biological sex differences in violence

Sex Differences in Impulsivity: A Meta-Analysis Catharine P. Cross, Lee T. Copping, and Anne Campbell Durham University Men are overrepresented in socially problematic behaviors, such as aggression and criminal behavior, which have been linked to impulsivity. Our review of impulsivity is organized around the tripartite theoretical distinction between reward hypersensitivity, punishment hyposensitivity, and inadequate effortful control. Drawing on evolutionary, criminological, developmental, and personality theories, we predicted that sex differences would be most pronounced in risky activities with men demonstrating greater sensation seeking, greater reward sensitivity, and lower punishment sensitivity. We predicted a small female advantage in effortful control. We analyzed 741 effect sizes from 277 studies, including psychometric and behavioral measures. Women were consistently more punishment sensitive (d 0.33), but men did not show greater reward sensitivity (d 0.01). Men showed significantly higher sensation seeking on questionnaire measures (d 0.41) and on a behavioral risk-taking task (d 0.36).

Questionnaire measures of deficits in effortful control showed a very modest effect size in the male direction (d 0.08). Sex differences were not found on delay discounting or executive function tasks.

The results indicate a stronger sex difference in motivational rather than effortful or executive forms of behavior control. Specifically, they support evolutionary and biological theories of risk taking predicated on sex differences in punishment sensitivity. A clearer understanding of sex differences in impulsivity depends upon recognizing important distinctions between sensation seeking and impulsivity, between executive and effortful forms of control, and between impulsivity as a deficit and as a trait.

Keywords:impulsivity, sex, sensation seeking, effortful control, reinforcement sensitivity Supplemental materials:http://dx.doi.org/10.1037/a0021591.supp Men engage in impulsive and risky behaviors more frequently than women. They die younger than women, and the higher male:female mortality ratio is particularly pronounced for deaths from external causes (Kruger & Nesse, 2006). Men drive more recklessly, with fully 97% of dangerous driving offenses commit- ted by men (Beattie, 2008; Norris, Matthews, & Riad, 2000). Men also have a significantly higher death rate from nonvehicle acci- dents such as falls, drowning, choking, electrocution, firearm accidents, and fires (Pampel, 2001). Violence-precipitated visits to hospital accident and emergency services are higher among men (Shepherd, 1990). Men are more physically and verbally aggres- sive than women across data sources and nations (Archer, 2004, 2009; Bettencourt & Miller, 1996; Eagly & Steffen, 1986; Hyde, 1986; Knight, Fabes, & Higgins, 1996; Knight, Guthrie, Page, & Fabes, 2002). Men constitute 76% of all criminal arrests in the United States, committing 89% of homicides and 82% of allviolent crime (U.S. Department of Justice, 2009). Worldwide, men use drugs (alcohol, tobacco, cannabis, and cocaine) more than women (Degenhardt et al., 2008). They participate more often in extreme sports, such as sky diving and mountain climbing (Harris, Jenkins, & Glaser, 2006; Robinson, 2008). Men are also more likely than women to suffer from a range of psychopathologies characterized by externalizing and impulsive behaviors such as antisocial personality disorder, conduct disorder, attention-deficit/ hyperactivity disorder, and intermittent explosive disorder (Amer- ican Psychiatric Association, 2000; Frank, 2000; Gershon & Ger- shon, 2002; Kessler et al., 2006; Moffitt, Caspi, Rutter, & Silva, 2001; Swanson, Bland, & Newman, 1994).

In all these domains, impulsivity has been invoked as an ex- planatory variable. Sometimes impulsivity is embedded in a theory or model, but more often it appears as an independent variable in regression analyses along with other plausible explanatory candi- dates. It is surprisingly rare, however, that sex differences in social and psychological pathologies have been considered in relation to sex differences in impulsivity in society at large. In the present study, we use meta-analysis to examine whether there are sex differences in unselected community samples across a range of psychometric and behavioral measures of impulsivity. We also examine whether, in these samples, variance in men’s impulsivity scores is greater than women’s. Such a finding could explain men’s overrepresentation in extreme and problematic impulsive behaviors. Indeed, although men would also be overrepresented at the left as well as the right tail of the distribution, low levels of impulsivity are unlikely to attract attention from educational, med- ical, or judicial systems.

Catharine P. Cross, Lee T. Copping, and Anne Campbell, Department of Psychology, Durham University, Stockton-on-Tees, United Kingdom.

We would like to thank Steven Muncer for statistical advice. Thanks also to all the authors who kindly provided data for inclusion in the analysis and to Joanne Campbell, Natalie Gray, and Trixie Lo for assistance with coding and proofreading. We are grateful to Roy Baumeister, Philip Corr, and Marvin Zuckerman for responding to theoretical and conceptual queries.

Correspondence concerning this article should be addressed to Catharine P. Cross, Department of Psychology, Durham University, Queens Campus, University Boulevard, Thornaby, Stockton-on-Tees TS17 6BH, United Kingdom. E-mail: [email protected] Psychological Bulletin© 2011 American Psychological Association 2011, Vol. 137, No. 1, 97–1300033-2909/11/$12.00 DOI: 10.1037/a0021591 97 This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Impulsivity: Models, Measures, and Sex Differences A terse, broad, and widely accepted definition of impulsivity is a “tendency to act spontaneously and without deliberation” (Carver, 2005, p. 313). However, the trait is far from unitary (Evenden, 1999), and Depue and Collins (1999, p. 495) noted that “impulsivity comprises a heterogeneous cluster of lower-order traits.” There have been a bewildering number of attempts to disaggregate impulsivity into more specific subtypes such as fail- ure to plan (Patton, Stanford, & Barratt, 1995), lack of persever- ance (Whiteside & Lynam, 2001), venturesomeness (H. J. Eysenck & Eysenck, 1985), poor self-discipline (Costa & McCrae, 1992), and novelty seeking (Cloninger, 1987).

In organizing our review of the literature, we focused on theo- retical approaches to impulsivity, highlighting the extent to which they emphasize overattraction to reward (strong approach motiva- tion), undersensitivity to punishment (weak avoidance motiva- tion), or problems with effortful or higher order control. In an automotive analogy, these can be thought of as a problem with a stuck accelerator, a problem of faulty brakes, or a problem of poor judgment by the driver. Many theoretical approaches to impulsiv- ity explicitly invoke this distinction between approach, avoidance, and higher order cognitive systems (Carver, 2005; Cloninger, 1987; Depue & Collins, 1999; Fowles, 1987; Gray, 1982; Nigg, 2001; Rothbart, Ahadi, & Evans, 2000). This tripartite distinction also dovetails with proposals made by evolutionary, developmen- tal, personality, criminological, and clinical psychologists about the source of sex differences in impulsivity. In this brief overview, we describe the various theoretical orientations and formulate predictions of likely sex differences. We also note measures that have been developed to assess the constructs that are included in our meta-analysis. These are summarized in Table 1. Some theo- rists have been explicit in their recognition and explanation of sex differences in impulsivity. In other cases, we have inferred sex differences via theorists’ proposed explanations of psychopathol- ogies that are more prevalent in one sex than the other.

Reward Sensitivity and Approach Motivation Evolutionary theory.Aggressive behavior, as we have noted, is considerably more frequent and serious among men.

Evolutionary approaches have been quite explicit in their predic- tions of sex differences in aggression. Across many species in- cluding our own, asymmetries of parental investment exert a significant impact on those aspects of psychology that have con- sequences for inclusive fitness. To the extent that effective polyg- yny was characteristic of hominid evolution (Archer, 2009; Larsen, 2003; Plavcan, 2001), men have had very high incentives for establishing intrasexual dominance as a means of securing a large number of mates and increasing their reproductive success (Daly & Wilson, 1983). This competition can take the form of direct aggression, with correspondingly increased rates of homi- cide and decreased life expectancy, especially among men who are young and unmarried (Daly & Wilson, 1988; Wilson & Daly, 1997). Wilson and Daly (1985) suggested that the psychological mechanism underlying this male-on-male aggression is an in- creased “taste for risk” among young men, a taste that also man- ifests itself in riskier decision making, gambling, dangerous driv- ing, and drug use. This formulation suggests that sex differencesshould be most marked in those impulsivity measures that include a component of sensation seeking or risk taking. In emphasizing the appetitive nature of motivation (i.e., the positive attractions of risk), this model also predicts sex differences in the sensitivity to reward associated with such risky enterprises.

Sensation seeking.Zuckerman’s (1979, p. 10) definition of sensation seeking as “the need for varied, novel, and complex sensations and experiences and the willingness to take physical and social risks for the sake of such experience” highlights the compelling attraction of novel experiences—an attraction of such intensity that the individual is willing to tolerate risks in their pursuit. Zuckerman and Kuhlman (2000, p. 1001) argued that “the approach gradient is higher and the avoidance gradient (anticipated anxiety) is lower in high sensation seekers than in low sensation seekers over the range of novel risk-taking activities.” Sex differ- ences have been found consistently on Zuckerman’s Sensation Seeking Scale (SSS; Zuckerman, 1994). These appear on the Thrill and Adventure, Boredom Susceptibility, and Disinhibition sub- scales but are absent on the Experience Seeking subscale, which measures preferences for new experiences that are not marked by risk (e.g., eating exotic food). A newer measure, the Impulsive Sensation Seeking (ImpSS) scale of the Zuckerman–Kuhlman Personality Questionnaire (ZKPQ), also shows sex differences, with men scoring higher (McDaniel & Zuckerman, 2003; Zucker- man, Kuhlman, Joireman, Teta, & Kraft, 1993). Sex differences in a range of risky behaviors were found to be completely mediated by the sex difference in impulsive sensation seeking (Zuckerman & Kuhlman, 2000).

Zuckerman (1989, 1994, 2007) has suggested that men’s role in mate competition and hunting is the distal factor driving this desire for risk. Testosterone levels are correlated with sensation seeking, as well as with prioritization of short-term goals, impulsivity, dominance, competition, and sexual arousal (Archer, 2006). In terms of central nervous system action, impulsive sensation seek- ing is proposed to result from the balance between the attraction of excitement and the avoidance of danger associated specifically with risky behaviors. The explanatory approach is biological:

Dopamine is involved in reward and approach behavior, whereas serotonin mediates restraint. Dopamine accelerates risky behavior because, when faced with danger, high-sensation seekers experi- ence stronger attraction than low-sensation seekers. Men’s greater sensation seeking chiefly results from a more reactive dopaminer- gic system (Zuckerman & Kuhlman, 2000). Zuckerman also ac- knowledges the relevance of inhibition mediated by the serotoner- gic system, but his chief emphasis is on the attractions of risk taking among men.

Criminology.In theirGeneral Theory of Crime, Gottfredson and Hirschi (1990) argued that the attractions of antisocial behav- ior are powerful, immediate, and evident. It is criminal desistance rather than involvement that requires explanation. They proposed that criminal behavior results from the interaction between attrac- tive criminal opportunities and low self-control. The effect size for low self-control on crime (d 0.41), in 21 empirical studies with 49,727 participants, ranks as “one of the strongest known corre- lates of crime” (Pratt & Cullen, 2000, p. 952).

Noting the ubiquitous sex differences in criminal behavior, Gottfredson and Hirschi (1990, p. 147) argued that greater self- control among women resulted from internalization of the stronger external and familial control exercised over daughters, rather than 98 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Table 1 Summary of Measurement Categories by Domain Category Measure Reward sensitivity Sensitivity to Reward and Sensitivity to Punishment Questionnaire (SPSRQ) and Generalized Reward and Punishment Expectancy Scales (GRAPES)SPSRQ (Torrubia et al., 2001): Reward scale; GRAPES (Ball & Zuckerman, 1990):

Reward scale Tridimensional Personality Questionnaire– Temperament and Character Inventory (TPQ– TCI) Reward Dependence TPQ (Cloninger, 1986): Reward scale; TCI (Center for Well-Being, n.d.): Reward scale Behavioral Activation System (BAS) Total BAS Scale (Carver & White, 1994): Total score BAS Drive BAS (Carver & White, 1994): Drive scale BAS Fun BAS (Carver & White, 1994): Fun Seeking scale BAS Reward BAS (Carver & White, 1994): Reward scale Punishment sensitivity SPSRQ and GRAPES SPSRQ (Torrubia et al., 2001): Punishment scale; GRAPES (Ball & Zuckerman, 1990):

Punishment scale TPQ–TCI Harm Avoidance TPQ (Cloninger, 1986): Harm Avoidance scale; TCI (Center for Well-Being, n.d.):

Harm Avoidance scale Behavioral Inhibition System (BIS) BIS Scale (Carver & White, 1994) Sensation seeking and risk taking Venturesomeness I 5(S. B. G. Eysenck & Eysenck, 1978) or I 6and I 7(S. B. G. Eysenck et al., 1985):

Venturesomeness scale Sensation Seeking Scale (SSS) Total SSS Form II (Zuckerman et al., 1964), Form IV (Zuckerman, 1971), or Form V (Zuckerman et al., 1978): Total score SSS Thrill and Adventure Seeking SSS Form IV (Zuckerman, 1971), Form V (Zuckerman et al., 1978), or Form VI (Zuckerman, 1984): Thrill and Adventure Seeking scale SSS Experience Seeking SSS Form IV (Zuckerman, 1971) or Form V (Zuckerman et al., 1978): Experience Seeking scale SSS Disinhibition SSS Form IV (Zuckerman, 1971), Form V (Zuckerman et al., 1978), or Form VI (Zuckerman, 1984): Disinhibition scale SSS Boredom Susceptibility SSS Form IV (Zuckerman, 1971) or Form V (Zuckerman et al., 1978): Boredom Susceptibility scale UPPS Sensation Seeking UPPS Impulsive Behavior Scale (Whiteside & Lynam, 2001): Sensation Seeking scale Dickman Functional Impulsivity (DIF) DIF (Dickman, 1990): Functional Impulsivity scale Risk Taking All measures of risk taking including the Jackson Personality Inventory (Jackson, 1994): Risk-Taking scale; Risky Impulsivity (Campbell & Muncer, 2009); and any measures developed for specific studies Zuckerman–Kuhlman Personality Questionnaire (ZKPQ) Impulsive Sensation Seeking ZKPQ (Zuckerman & Kuhlman, 1993): Impulsive Sensation Seeking scale Karolinska Scales of Personality (KSP) Monotony Avoidance KSP (Schalling, 1978): Monotony Avoidance scale Multidimensional Personality Questionnaire– Personality Research Form (MPQ–PRF) Harm Avoidance MPQ (Tellegen, 1982) or PRF (Jackson, 1994): Harm Avoidance scale Sensation Seeking (other measures) Anymeasure of sensation seeking not specified elsewhere, including the Tridimensional Personality Questionnaire (Cloninger, 1986): Novelty Seeking scale; the Arnett Inventory of Sensation Seeking (Arnett, 1994); and any measures developed for specific studies Effortful control: General measures of impulsivity Eysenck measures of impulsiveness I 5(S. B. G. Eysenck & Eysenck, 1978) or I 6and I 7(S. B. G. Eysenck et al., 1985); Eysenck Personality Inventory (H. J. Eysenck & Eysenck, 1968): Impulsiveness scale Barratt Impulsiveness Scale (BIS) Total BIS-10 (Barratt, 1985), BIS-11 (Patton, Stanford, & Barratt, 1995): aTotal score Karolinska Scales of Personality (KSP) Impulsivity KSP (Schalling, 1978): Impulsivity scale Other measures Any measure of impulsivity not specified elsewhere, including Personality Research Form (Jackson, 1994): Impulsivity scale; NEO Personality Inventory–Revised (Costa & McCrae, 1992): Impulsivity facet, Self-Discipline and Deliberation scales; and any measures developed for specific studies in the review Effortful control: Specific forms of impulsivity BIS Cognitive BIS-10 (Barratt, 1985), BIS-11 (Patton et al., 1995): aCognitive/Attentional Impulsiveness scale BIS Motor BIS-10 (Barratt, 1985), BIS-11 (Patton et al., 1995):

aMotor Impulsiveness scale BIS Non-Planning BIS-10 (Barratt, 1985), BIS-11 (Patton et al., 1995):aNon-Planning Impulsiveness scale UPPS PerseveranceUPPS Impulsive Behavior Scale (Whiteside & Lynam, 2001): Lack of Perseverance scale (table continues) 99 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. sons. Rejecting the need for sex-specific explanations of crime, they argued that self-control was equally relevant to offending by men and women, and this contention has been substantiated (Blackwell & Piquero, 2005; Burton, Cullen, Evans, Alarid, & Dunaway, 1998; Keane, Maxim, & Teevan, 1993; Piquero & Rosay, 1998; Pratt & Cullen, 2000; Tittle, Ward, & Grasmick, 2003). Women have greater self-control than men (Keane et al., 1993; Nakhaie, Silverman, & LaGrange, 2000; Tittle et al., 2003); and a strong hypothesis from the general theory of crime is that, when self-control is controlled, sex differences in criminal or delinquent involvement will become nonsignificant. This has been found in some studies (Burton et al., 1998; Tittle et al., 2003).

Even when it has not eliminated the effect of sex, it has reduced it substantially (LaGrange & Silverman, 1999; Nakhaie et al., 2000).

Low self-control has been measured as a combination of impul- sivity, risk seeking, preference for simple tasks and physical ac- tivities, temper, and self-centeredness (Grasmick, Tittle, Bursik, & Arneklev, 1993). However, a number of researchers have found the impulsivity and risk-seeking subscales to be almost as predic- tive as the full scale (Arneklev, Grasmick, Tittle, & Bursik, 1993; Deschenes & Esbensen, 1999; Longshore, Turner Rand, & Stein, 1996; Nakhaie et al., 2000; Piquero & Rosay, 1998; P. B. Wood, Pfefferbaum, & Arneklev, 1993). Of the two traits, risk seeking shows the stronger association with crime (LaGrange & Silver- man, 1999; Nakhaie et al., 2000). Together with Gottfredson and Hirschi’s (1990, p. 89) emphasis upon the implicit attractions of crime (“money without work, sex without courtship, revenge with- out court delays”), we therefore discuss this theory as representing an approach orientation to impulsivity.

Three-factor theories.Cloninger (1987) has advanced a biopsychological model of personality in the field of psychiatry.

He originally postulated three genetically mediated, independentdimensions of personality: novelty seeking, harm avoidance, and reward dependence. The original measure of these traits was the Tridimensional Personality Questionnaire (TPQ), which was sub- sequently modified and renamed the Temperament and Character Inventory (TCI). Variations in the balance of these sensitivities have been used to explain a range of mental illnesses. Cloninger uses the termnovelty seekingas an alternative to impulsivity, clearly identifying its appetitive motivation (Cloninger, 1986).

Novelty seeking is associated with activity in the dopaminergic reward system and is expressed as a tendency to respond to novel stimuli with excitement. The scale is composed of four facets:

Exploratory Excitability, Impulsiveness, Extravagance, and Disor- derliness. This form of impulsivity bears a strong resemblance to sensation seeking: Not only does it correlate highly (r .68) with the Zuckerman’s ImpSS scale, but both scales correlate negatively with monoamine oxidase levels, suggesting a common biological basis (Zuckerman & Cloninger, 1996). However, unlike for sen- sation seeking, no sex difference was found for novelty seeking (d 0.04) in a recent meta-analysis (Miettunen, Veijola, Lau- ronen, Kantoja¨ rvi, & Joukamaa, 2007).

H. J. Eysenck and Eysenck’s (1968) early two-factor personality theory identified impulsivity as a component of extraversion, linked to low cortical arousal and a consequent need for stimula- tion (resulting in sensation seeking). Impulsivity was later disag- gregated into two components: impulsiveness (poor impulse con- trol) and venturesomeness (stimulus hunger). The I 7inventory was developed to measure impulsiveness and venturesomeness as dis- tinct traits (S. B. G. Eysenck, 1993).

Venturesomeness shares the original quality of stimulus hunger, reflecting approach motivation, and hence S. B. G. Eysenck (1993) aligned it with extraversion. However, evidence suggests it is more closely associated with the psychoticism dimension of tough- Table 1 (continued) Category Measure UPPS Premeditation UPPS Impulsive Behavior Scale (Whiteside & Lynam, 2001): Lack of Premeditation scale UPPS Urgency UPPS Impulsive Behavior Scale (Whiteside & Lynam, 2001): Urgency scale Dickman Dysfunctional Impulsivity (DDI) DDI (Dickman, 1990): Dysfunctional Impulsivity scale Impulse Control Any measure of impulse control, including the Offer Self-Image Questionnaire (Offer et al., 1982): Impulse Control scale; MPQ (Tellegen, 1982): Control scale; and any measures developed for specific studies in the review Social Problem Solving Inventory–Revised (SPSI–R) SPSI–R (D’Zurilla et al., 1996): aImpulsivity/Carelessness Style scale Effortful control: Behavioral measures of impulsivity Balloon Analogue Risk Task (BART) BART (Lejuez et al., 2002) Delay Discounting Any delay discounting task (see, e.g., Mazur, 1987; Richards et al., 1999) using real or hypothetical rewards including money, sweets, and cigarettes Executive response inhibition Stop Signal task (Logan et al., 1997), Go/No-Go task (Newman et al., 1985), any Stroop-based task (Stroop, 1935), Continuous Performance Test (Conners, 2000), and Inhibitory Reach task (Enticott et al., 2006) Iowa Gambling Task (IGT) IGT (Bechara et al., 1994) Visual–cognitive tasks Matching Familiar Figures Test (Kagan et al., 1964), Intradimensional/Extradimensional learning task (Roberts et al., 1988), Tower of London Test (Shallice, 1982), Porteus Maze (Porteus, 1950), Trail Making Test (Reitan, 1958), Visual Comparison Task (Dickman & Meyer, 1988), and Spatial Orientation Dynamic Test–Revised (Colom et al., 2003) Note.UPPS Urgency, Premeditation, Perseverance, and Sensation Seeking. aIncludes versions translated into other languages.

100 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. mindedness, hostility, and nonconformity. Indeed Zuckerman (1989) suggested that the psychoticism factor really represents his dimension of impulsive sensation seeking. In support of this con- tention, the ImpSS scale loads strongly on a psychoticism factor, the best marker of which is Eysenck’s Psychoticism scale (Zuck- erman et al., 1993). In terms of item content, the Venturesomeness scale resembles sensation seeking, rather than impulsiveness (Zuckerman, 1989). Men score higher than women on Venture- someness (S. B. G. Eysenck, Pearson, Easting, & Allsopp, 1985), and it is positively correlated with the male hormone testosterone (Aluja & Torrubia, 2004; Coccaro, Beresford, Minar, Kaskow, & Geracioti, 2007; Daitzman & Zuckerman, 1980). As with Zucker- man’s sensation seeking, we anticipate that Venturesomeness will show a sex difference in the male direction.

Reinforcement sensitivity theory.Gray (1970, 1982), a former student of Eysenck’s, proposed that extraversion and neu- roticism should be rotated to form two new dimensions reflecting sensitivity to punishment (anxiety, associated with introversion and neuroticism) and sensitivity to reward (impulsivity, associated with extraversion and neuroticism). These new dimensions came to be called, respectively, the behavioral inhibition system (BIS) and the behavioral activation system (BAS).

Approach motivation is controlled by BAS, which is sensitive to signals of unconditioned and conditioned reward, nonpunishment, and escape from punishment. Gray labeled the personality mani- festation of the BAS dimension as “impulsivity,” indicating that heightened reward sensitivity was viewed as the key source of impulsive behavior. Note that Gray’s reward sensitivity is not restricted to reward associated with sensation seeking or other risky enterprises: Activity in the BAS causes movement toward goals more generally. Emotionally, this system generates feelings of hope, elation, and satisfaction. Dopaminergic pathways, espe- cially between the ventral tegmental area of the midbrain and the nucleus accumbens, are implicated in its functioning. Gray made no specific predictions in his theory regarding sex differences, although, like Eysenck, his formulation addressed clinical disor- ders where sex differences are well established. Gray’s theory has been studied extensively in relation to psychopathy, a predomi- nantly male disorder (Cale & Lilienfeld, 2002). Patterson and Newman (1993) argued that the oversensitivity of psychopathic individuals to reward results in hyperarousal and a consequent failure to pause and reflect when reinforcers are withdrawn. This process results in dysfunctional perseveration in mixed-incentive situations.

Measures of reward sensitivity and approach motivation.

Carver and White’s (1994) BIS and BAS psychometric scales have been widely used to assess Gray’s two dimensions of tempera- ment. The BAS scale factors into three subscales: Reward Respon- siveness (emotional enjoyment of reward), Drive (the pursuit of appetitive goals), and Fun Seeking (the tendency to seek out new, potentially rewarding experiences). Clearly this last scale overlaps considerably with aspects of sensation seeking; some work sug- gests that, unlike the other two BAS scales, it loads on a separate factor that has been called “rash impulsiveness” (Dawe, Gullo, & Loxton, 2004; Franken & Muris, 2006; Quilty & Oakman, 2004).

Torrubia, A´ vila, Molto´ , and Caseras (2001) developed another pair of scales to measure Gray’s two dimensions: the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ).

SPSRQ Sensitivity to Reward is correlated with Eysenck’s I 7 Impulsiveness, Zuckerman’s SSS, and Excitement Seeking in the five-factor model (J. T. Mitchell et al., 2007). The Reward scale from the Generalized Reward and Punishment Expectancy Scales (GRAPES; Ball & Zuckerman, 1990) has also been used, and shows a positive correlation with sensation seeking. A recent meta-analysis (Miettunen et al., 2007) found that women scored higher than men (d 0.63) on the Reward Dependency scale of Cloninger’s TCI, although there are important differences in item content between this and the other reward dependence measures that are discussed later.

The two most widely used measures of sensation seeking and risk taking are Eysenck’s I 7Venturesomeness scale and Zucker- man’s SSS. The Monotony Avoidance scale of the Karolinska Scales of Personality (KSP) also captures the intolerance of bore- dom that corresponds to the SSS Boredom Susceptibility subscale.

The more recent ZKPQ contains a scale of Impulsive Sensation Seeking. Dickman (1990) distinguished between Dysfunctional Impulsivity (a tendency to act with less foresight than others, leading the individual into difficult situations) and Functional Impulsivity (a tendency to respond quickly when the situation is optimal, such as taking advantages of unexpected opportunities).

These form separate scales on the Dickman Impulsivity Inventory.

Those who score high on Functional Impulsivity are characterized as “enthusiastic, active individuals who are willing to take risks” (Dickman, 1990, p. 98). This suggests, and data confirm, that functional impulsivity is closely aligned with sensation seeking:

We therefore consider it with other sensation-seeking measures.

Other measures of sensation seeking include the UPPS Sensation Seeking scale, which resulted from Whiteside and Lynam’s (2001) factor analysis of 21 impulsivity scales. Tellegen’s (1982) Multi- dimensional Personality Questionnaire (MPQ) also contains a sub- scale of Harm Avoidance, the items and structure of which corre- spond to reversed sensation seeking. We analyzed it together with other sensation-seeking measures (see Table 1). Punishment Insensitivity and Avoidance Motivation Here we consider approaches to impulsivity that highlight a hyposensitivity to the negative consequences of impulsive acts.

These are distinguished from approaches that view impulsivity as a failure of effortful control (which we discuss later) by virtue of the fact that they deal with deficits in reactive or motivational, rather than cognitive, control.

Evolutionary theory.Campbell (1999, 2002) proposed an evolutionary account, complementary to that of Daly and Wilson (1988), that focuses on female disincentives for risk. Women’s reproductive success depends to a greater extent than men’s upon avoiding injury and death. This results from infants’ greater de- pendence on the mother than on the father, women’s higher pa- rental investment in each offspring, and the limited number of offspring that a woman can bear in a lifetime. Hence women should be more sensitive to and more avoidant of danger than men, an effect that is mediated by higher levels of fear about physical injury or death. Cross-culturally, fear is experienced more in- tensely and frequently by women than by men (Brebner, 2003; Fischer & Manstead, 2000). As with Daly and Wilson’s formula- tion, the prediction is that sex differences will be manifest in those impulsivity inventories that contain an element of risk. But be- cause Campbell’s proposed mediating variable is fear, her account 101 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. predicts greater harm avoidance in women than in men, and possibly greater sensitivity to punishment reflected in higher BIS scores.

Three-factor theories.In Cloninger’s tripartite theory, harm avoidance is mediated by activity in a serotonergic punishment system and is manifest in a tendency to respond strongly to signals of aversive stimuli by inhibiting ongoing behavior. High scorers are “cautious, tense, apprehensive, fearful, inhibited, shy, easily fatigable, and apprehensive worriers” (Cloninger, 1987, p. 576). A recent meta-analysis (Miettunen et al., 2007) reported a small to moderate effect size favoring women on Harm Avoidance (d 0.33).

When Eysenck disaggregated impulsivity, he aligned impulsive- ness with psychoticism, a dimension characterized by insensitivity to punishment, poor impulse control, and a tendency to respond without regard to interpersonal consequences (H. J. Eysenck & Gudjonsson, 1989). However, impulsiveness is not associated with testosterone, as would be expected of a facet of psychoticism (Aluja & Torrubia, 2004; Coccaro et al., 2007; Daitzman & Zuck- erman, 1980), and norms for impulsiveness show no sex differ- ences (S. B. G. Eysenck et al., 1985).

Reinforcement sensitivity theory.Gray’s (1970) theory pro- posed that behavior was governed by the balance between three motivational systems. He identified the BAS system, described earlier, as the basis for impulsivity. The behavioral avoidance system (BIS) is an aversive motivational system that is sensitive to signals of punishment, nonreward, and novelty. Activity in the BIS inhibits behavior. Emotionally, the system is associated with feel- ings of fear, anxiety, and frustration. The BIS has been localized to the right anterior cortex. Gray also argued for a third, flight or fight system sensitive to innately aversive stimuli and associated with Eysenck’s third dimension of psychoticism.

In a subsequent revision of the theory (Gray & McNaughton, 2000), the flight or fight system, associated with fear, became responsible for avoidance as well as escape behaviors. The BIS, associated with anxiety, became responsible for resolving motiva- tional conflicts between approach and avoidance. The BAS re- mained relatively unaltered. However, these revisions, including the distinction between fear- and anxiety-related avoidance pro- cesses and the new role of the BIS, have not been reflected in personality inventories used to assess punishment sensitivity (but see Heym, Ferguson, & Lawrence, 2008; Perkins & Corr, 2006).

Most researchers continue to work with Gray’s original formula- tion (Bijttebier, Beck, Claes, & Vandereycken, 2009; Smillie, 2008).

As noted, Gray’s work has been applied to psychopathy. Al- though Gray proposed that overactive BAS was the source of impulsivity, Lykken (1957) suggested that the lack of fear found in psychopathic individuals resulted in a failure to form classically conditioned associations between fear and rule breaking. Thus, such individuals lack the normal negative reinforcer (fear reduc- tion) required for active and passive avoidance learning. Fowles (1988) suggested that individuals with psychopathy have a weak BIS and hence perform particularly poorly when passive avoid- ance (inhibition of a response) is required. A distinction has been made between primary and secondary psychopathy that may unite these different positions. Primary psychopaths, who correspond to the popular stereotype of the disorder, experience low levels of anxiety (weak BIS), which give rise to their antisocial actions(Lykken, 1995). Secondary psychopaths, however, experience heightened negative emotions and are hyperresponsive to oppor- tunities for reward reflected in stronger BAS (but normal BIS) reactivity. This proposal has recently received empirical support (Newman, MacCoon, Vaughn, & Sadeh, 2005; Ross et al., 2007; Wallace, Malterer, & Newman, 2009).

In sharp contrast to psychopathy, anxiety disorders are found more often in women than in men (Frank, 2000), and anxiety was the original focus of Gray’s (1982) BIS punishment hypersensi- tivity formulation. A considerable body of work has established that anxiety is associated with preferential attention to threatening stimuli. Orienting responses occur before the nature or meaning of the stimuli is consciously registered, indicating the engagement of low-level reactive processes that are automatic, unintentional, and unconscious (Bar-Haim, Lamy, Pergamin, Bakermans- Kranenburg, & van IJzendoorn, 2007). This attentional bias has been shown both in patients suffering from a range of anxiety disorders (Barlow, 2002) and in nonclinical samples high in trait anxiety (Mogg et al., 2000). Among people suffering from depres- sion, women and girls more frequently ruminate about negative life events, which both exacerbates depressive symptoms and indicates an attentional preoccupation with punishment (Rood, Roelofs, Bögels, Nolen-Hoeksema, & Schouten, 2009). Given women’s higher levels of subclinical anxiety and depression (Costa, Terracciano, & McCrae, 2001), we expect women to be particularly sensitive to cues of punishment.

Measures of punishment sensitivity.Carver and White’s (1994) BIS and BAS psychometric scales include a single BIS scale that measures sensitivity to signals of punishment. This scale correlates with measures of negative affectivity, negative temper- ament, and anxiety. Torrubia et al.’s (2001) SPSRQ Sensitivity to Punishment scale is correlated with Carver and White’s BIS and with harm avoidance and anxiety (see also Caseras, A´ vila, & Torrubia, 2003). Punishment sensitivity as measured by GRAPES correlates significantly with the BIS scale and anxiety (Gomez & Gomez, 2005). The TPQ–TCI measure of harm avoidance assesses an individual’s tendency to respond intensively to signals of aver- sive stimuli by inhibiting or stopping behavior (Cloninger, 1987).

We include it as a measure of punishment sensitivity. (Note that the identically named scale from the MPQ measures reversed sensation seeking; see Table 1.) Effortful Control Effortful control describes the “ability to choose a course of action under conditions of conflict, to plan for the future, and to detect errors” (Rothbart, 2007, p. 207). Behaviorally, it is defined as the ability to inhibit a dominant response and perform a sub- dominant response. It is a major form of self-regulation manifested as conscious or effortful decision making in the service of longer term objectives. It is the planfulness and executive nature of this ability that distinguishes it from the reactive or motivational the- ories that we have previously described.

Evolutionary.MacDonald (2008) argued that although evo- lution has shaped dedicated psychological modules (adaptations) to solve recurrent evolutionary problems, the effortful control system can inhibit such “automatic” evolved responses and thereby reduce impulsivity. MacDonald argued for sex differences in impulsivity based on strong sexual selection for male intra- 102 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. sexual competition, which makes approach tendencies less ame- nable to override by effortful control: “Males are thus expected to be higher on behavioral approach systems (sensation seeking, impulsivity, reward seeking, aggression) and therefore on ave- rage be less prone to control prepotent approach responses” (MacDonald, 2008, p. 1018). This sex difference should be par- ticularly marked during adolescence and young adulthood, when reproductive and competitive drives are strongest. In addition, future discounting (a preference for immediate rather than delayed reward) may be adaptive for individuals growing up in highly stressful environments and may underlie the sex difference in risk taking (Kruger & Nesse, 2006; Wilson & Daly, 1997).

Bjorklund and Kipp’s (1996) proposal of evolved sex differ- ences in impulsivity was not restricted to the domains of aggres- sion and risk taking. They argued that inhibitory ability was especially critical to women’s reproductive success in relation to mate choice and offspring care. Because women contribute the lion’s share of parental investment, selectivity in mate choice is more important to women. This makes the ability to conceal sexual interest advantageous in the service of evaluating long-term mate prospects. Women can gain additional genetic and material re- sources from clandestine copulations; thus, inhibitory control over the “leaked” expression of sexual interest in other men would be beneficial in securing the commitment of a long-term partner. In addition, the protracted dependency of offspring places strain on a mother’s self-control. She must prioritize the infant’s needs over her own, inhibit aggressive impulses toward it, and delay her own gratification—all of which would be aided by improved inhibitory control. Bjorklund and Kipp proposed that women’s advantage in inhibition would be relatively domain specific, evident only in those tasks that assayed social and emotional restraint. Their narrative review supported this hypothesis, concluding that wom- en’s greater inhibition was evident in the social domain (e.g., facial and bodily concealment of feelings), present though less strong in the behavioral domain (e.g., resistance to temptation), and absent in cognitive inhibition (e.g., Stroop test, memory interference, selective attention). This proposal predicts a female advantage in inhibitory control specifically in interpersonal domains.

Developmental.Rothbart and colleagues (Rothbart & Bates, 2006; Rothbart & Derryberry, 1981; Rothbart & Posner, 2006) explored the concept of effortful control as a form of self- regulation from a developmental perspective. Their model includes lower level motivational approaches but is distinguished by its emphasis on the child’s acquisition of higher level cognitive con- trol of impulsivity. In the early months, infants are primarily reactive to events; the two dimensions that capture variation in their temperamental responses map onto Gray’s BIS and BAS systems (Rothbart, 2007; Rothbart et al., 2000). These have been measured by scales assessing negative affectivity and surgency– extraversion, corresponding to BIS and BAS, respectively. To- gether these two systems modulate avoidance and approach be- havior. With increasing age the child develops effortful control, a form of self-regulatory executive control in the affective domain (MacDonald, 2008). This system is superordinate to the more primitive motivational systems, allowing the individual to sup- press reactive tendencies in the service of longer term objectives.

Attention shifting and behavioral inhibition allow the child to suppress prepotent but inappropriate behavior. The likely site of these processes is the ventromedial prefrontal cortex, particularlythe orbitofrontal cortex and the ventral anterior cingulated cortex (MacDonald, 2008; Posner & Rothbart, 2009).

Lower and higher level systems are not wholly independent because “the motivational circuits can function as specialized learning mechanisms, guiding the development of cortical repre- sentations in light of underlying appetitive and defensive needs” (Derryberry & Rothbart, 1997, p. 639). Cross-lagged correlations have been reported between early fear and later effortful control (e.g., Kochanska & Knaack, 2003). These patterns of association are attributed to the greater amenability of more fearful children to parental socialization practices (Derryberry & Rothbart, 1997).

Girls are more fearful than boys (Else-Quest, Hyde, Goldsmith, & Van Hulle, 2006; Hsu, Soong, Stigler, Hong, & Liang, 1981; Maziade, Boudreault, Thivierge, Cape´ raa`,&Coˆte´ , 1984); girls may therefore exceed boys in effortful control. Else-Quest et al.’s (2006) meta-analysis of childhood temperament differences re- vealed a large effect size favoring girls for effortful control (d 1.01). However, this dimension is a composite of scales from the Child Behavior Questionnaire, reflecting an easygoing, low- demand temperament that is apparently more characteristic of girls than boys. Impulsivity is measured separately as a subscale of the Surgency/Extraversion dimension, which broadly corresponds to BAS or approach motivation, showing a smaller effect size in the male direction (d 0.18).

The development of the prefrontal cortex that mediates effortful control continues through adolescence and into adulthood (Casey, Getz, & Galvan, 2008; Sternberg, 2007). Although impulsive behavior in childhood may result from the balance between the two lower level reactive systems, in adulthood it is likely to be associated with weak or ineffective effortful control (Posner & Rothbart, 2009). Baumeister and colleagues (Baumeister, Vohs, & Tice, 2007; Muraven & Baumeister, 2000) used the termself- controlto refer to control over thoughts, emotions, performance, and impulses. Self-control bears a strong similarity to effortful control, and indeed Baumeister et al. (2007, p. 351) described it as a “deliberate, conscious, effortful subset of self-regulation.” It is assessed as an amalgam of self-discipline, deliberate– nonimpulsive action, reliability, healthy habits, and work ethic (Tangney, Baumeister, & Boone, 2004). Although sex differences have not been the focus of such research, R. F. Baumeister (per- sonal communication, February 18, 2010) has suggested a likely female advantage in self-control as a result of men’s stronger impulses, especially in the domains of sex and aggression.

Measuring effortful control: Behavioral tasks.Effortful control has been studied via laboratory tasks (see Table 2 for a summary of tasks included in the present analysis). The range of tasks has been wide, and the specific processes on which they depend are underspecified. In some cases, the conceptual link to impulsivity seems tenuous. Post hoc attempts to classify them empirically have not produced consistent findings, probably as a result of the different tasks selected for inclusion in the analyses (e.g., Kindlon, Mezzacappa, & Earls, 1995; Lane, Cherek, Rhodes, Pietras, & Tcheremissine, 2003; Meda et al., 2009; Reynolds, Ortengren, Richards, & de Wit, 2006; Reynolds, Penfold, & Patak, 2008). It is generally agreed that effortful control has two impor- tant characteristics: It involves the conscious suppression of a prepotent or dominant response, and it permits individuals to take a longer time perspective with regard to their actions. The distinc- tion between these forms of control has been supported in factor- 103 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Table 2 Summary of Behavioral Tasks of Impulsivity Task Summary Executive response inhibition Go/No-Go Two randomly alternating stimuli are presented (e.g., a car and a house). The participant is instructed to respond selectively to one but not the other by pressing a button. One stimulus is presented more frequently to establish a prepotent response. Commission errors index impulsivity.

Stop Signal Similar to the Go/No-Go task, but on some trials a signal (usually auditory) is given immediately after the critical target stimulus. On these trials, the participant must inhibit his or her response. The delay between the onset of the stimulus and the onset of the signal to stop is varied until participants successfully inhibit their go responses on 50% of trials. At this point, stop signal reaction time (SSRT) is estimated as the difference between the stop signal delay and the mean go reaction time. Longer SSRTs index higher impulsivity.

Continuous Performance Test Letters appear one at a time on a screen. The participant must press a button when a particular sequential configuration (e.g.,Cfollowed byA) is shown. Commission errors index impulsivity.

Stroop In the control condition, the participant names aloud the ink color of a row ofXs as quickly as possible. In the interference condition that follows, the participant must name aloud the ink color in which a series of words is written: Each word is a color name (e.g., red) that is different from the ink color (e.g., blue) used to print it. The two conditions are compared, and the disparity between them is a measure of the time taken to resolve the conflict between an automatic, nondesired response (word reading) and a nonautomatic, desired response (color naming). Hence a larger value indexes lower effortful control. Some researchers also use errors or time taken in the interference condition.

Visual–cognitive Matching Familiar Figures Test (MFFT) A target design is presented together with a number of similar designs. The task is to match the target with its identical version. Speed and errors reflect impulsivity.

Visual Comparison Similar to MFFT, but the participant is presented with two very similar figures and makes a “same” or “different” decision.

Trail Making Test The participant draws lines joining 25 circles distributed over a sheet of paper. In Part A, the circles are numbered 1–25, and the participant connects the numbers in ascending order. In Part B, the circles include both numbers (1–13) and letters (A–L). The participant is asked to alternate between numbers and letters (i.e., 1–A–2–B–3–C, etc.). The participant is instructed to work quickly and not to lift the pen from the paper. Errors are pointed out to the participant, and correction is allowed. Errors affect the score by increasing the time taken to complete the task. The time taken for Part A is subtracted from the time taken for Part B. A smaller value reflects impulsivity.

Porteus Maze This is a graded set of paper forms on which the participant traces the way from a starting point to an exit, avoiding blind alleys. There are no time limits. The mazes vary in complexity from simple diamond shapes to intricate labyrinths. TheQscore, used to index impulsivity, is obtained by measuring the number of times the pencil is lifted, touches the boundary, etc.

Circle Tracing Participants are asked to trace over a 9-in. circle as slowly as they can. The start and stop position are clearly marked on the circle in bright letters. Impulsivity is indexed by time taken to perform the task on the second trial.

Spatial Orientation Dynamic Test–Revised A computerized task in which participants move a red and a blue dot toward a specific destination. The program sets a course for the two dots that can be modified by pressing arrow buttons for each of the dots. The dependent measure is the mean deviation (in degrees) between the course of each of the moving dots at the end of the trial and the course it should have taken to reach its destination. Impulsivity is indexed as a high mean deviation.

Tower of London Test A board presents colored disks or beads arranged on three vertical pegs. These form a target array that the participant must try to replicate on his or her own board where the disks or beads are arrayed differently across the three pegs. Measures include preplanning time (time between seeing the disks and making the first move), errors on the first move, average move time (time spent on executing the plan), trials solved in the minimum number of possible moves or within a specified time limit, and excess moves (number of moves in excess of the minimum necessary to complete the task).

Intradimensional/Extradimensional Shift Two dimensions (color-filled shapes and white lines) are used. Simple stimuli use only one of these dimensions, whereas compound stimuli are made up of both (e.g., white lines overlaying color-filled shapes). The participant starts by seeing two simple color-filled shapes and must learn which one is correct by touching it. Through feedback, the participant learns which stimulus is correct. After six correct responses, the stimuli and/or rules are changed.

These shifts are initially intradimensional (e.g., color-filled shapes remain the only relevant dimension), then extradimensional (white lines become the only relevant dimension). The test has a number of outcome measures (including errors and numbers of trials and stages completed) that index impulsivity. 104 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. analytic studies of behavioral tasks (Lane et al., 2003; Reynolds, Ortengren, et al., 2006; Reynolds et al., 2008) and by neuroimag- ing studies that implicate different neural pathways for the two processes (Band & van Boxtel, 1999; McClure, Laibson, Loewen- stein, & Cohen, 2004).

Four tasks have been widely interpreted as assessing the ability to suppress a dominant or prepotent response, which we refer to as executive response inhibition(Conners, 2000; Kindlon et al., 1995; Lane et al., 2003; Nigg, 2001; Reynolds et al., 2008; Reynolds, Richards, & de Wit, 2006). These are the Go/No-Go task, the Stop Signal task, the Stroop test, and the Continuous Performance Test.

These tasks may also be sensitive to failure of interference pro- tection and to inattention (Dougherty et al., 2009; Reynolds et al., 2008).

A second quality of effortful control is the ability to select actions by taking into account their long-term rather than imme- diate consequences. Individual differences in time horizons have been assessed chiefly by behavioral tasks in which a choice must be made between a larger long-term and a smaller short-term reward (Lane et al., 2003; Reynolds et al., 2008). The most popular measures are the Delay Discounting task and its variants. More impulsive individuals are believed to show a steeper rate of discounting. The Iowa Gambling Task (IGT) has also been inter- preted as assessing time perspectives with regard to reward (Bec- hara, Damasio, Tranel, & Damasio, 1997). More impulsive indi- viduals persist in their attraction to short-term higher rewards despite the long-term loss to which this strategy leads. The Balloon Analogue Risk Task (BART) assesses a participant’s willingness to risk loss in the service of winning a higher monetary reward (Lejuez et al., 2002) and has been found to load on a commonfactor with delay discounting (Reynolds, Ortengren, et al., 2006; but see Meda et al., 2009). These three tasks are distinguished from lower level, automatic responses to reward or punishment on the basis that the tasks require a conscious and deliberate decision.

Other tasks used to assess impulsivity do not clearly align themselves with the distinction between behavioral disinhibition and time horizons. We refer to these asvisual– cognitive tasks because they are united by their use of visual attention paradigms to explore various aspects of executive function including plan- ning, set formation and switching, and motor control. Most infer impulsivity from the number of errors made on the task, based on the assumption that impulsive individuals tend to trade speed for accuracy, although this proposal has been controversial (Block, Block, & Harrington, 1974; Dickman & Meyer, 1988; Malle & Neubauer, 1991; Quiroga et al., 2007; Wilding, Pankhania, & Williams, 2007).

Measuring effortful control: Psychometric measures.The two cardinal aspects of impulsivity, failure to inhibit a prepotent response (e.g., “I say things without thinking”) and short time horizons (e.g., “I plan trips well ahead of time”; reverse scored), also appear as items in psychometric inventories. However, the two components are not always distinguished as separate scales.

The two most commonly used inventories of general impulsivity are the Eysenck’s Impulsiveness questionnaires (I 5,I6,I7, and the Eysenck Personality Inventory) and the total score from the Barratt Impulsiveness Scale. We also consider the Impulsivity scale of the KSP as a general measure of impulsivity.

In addition to these global measures, there is an arsenal of measures for assessing subtypes of impulsivity. Many of these have been derived from factor analyses of novel or extant items Table 2 (continued) Task Summary Delay Discounting The participant makes a series of dichotomous choices between a “standard” (e.g., $10 available after one of six delays: 0, 7, 30, 90, 180, 365 days) and an “alternative” sum of money available immediately (e.g., 23 values between $0.01 and $10.50), resulting, in this case, in 137 choices.

The choices are presented in random order. The indifference point or switch point (the point at which the participant prefers the immediate to the delayed reward) is determined for each level of the standards. This can be used to calculatek, the rate at which the standard of $10 is discounted as a function of delay. Impulsive individuals show lower switch points and a higher value ofk(a steeper rate of discounting) than less impulsive individuals. Variations on this task include the Probability Discounting task (which uses probabilistic rather than delayed rewards) and the Experiential Delay task (in which participants choose between a probabilistic delayed sum and a smaller sum that is immediate and certain).

Iowa Gambling Task The participant is shown four decks of cards. Each card informs the participant of a win, or a simultaneous win and loss of money. Two “disadvantageous” card decks (AandB) yield high monetary rewards but higher occasional losses. Two “advantageous” decks (CandD) yield low rewards but lower occasional penalties. Impulsive individuals continue to choose from the disadvantageous decks despite the long-term loss to which this strategy leads. The outcome measure is normally the number of draws from disadvantageous packs (AandB) subtracted from advantageous packs (CandD). This is taken as a measure of impulsivity manifest in a preference for short-term gains in spite of long-term losses.

Balloon Analogue Risk Task A computer screen shows a balloon and pump. Each click on the pump inflates the balloon and, with each pump, 5 cents is earned in an invisible temporary reserve. Participants are told that at some point each balloon will explode. When a balloon is pumped past its explosion point, an audible “pop” signals that all the money in the temporary reserve is lost. At any point during a trial, the participant can stop pumping the balloon and transfer the money in the reserve to the permanent bank. After each balloon explosion or money transfer, a new balloon appears. The dependent measure is normally the average number of pumps excluding balloons that exploded (i.e., the average number of pumps on each balloon prior to money collection). This reflects a tendency to continue with balloon inflation despite the risk of losing the money already won on that trial. 105 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. and scales. Because the factor solution depends on the selection of scales included, there is little consensus on the fundamental di- mensions of impulsivity. We now briefly describe some of the major conceptual distinctions that we include as measures of specific impulsivity.

The Barratt Impulsiveness Scale (the most recent version of which is the BIS-11; see Patton et al., 1995; Stanford et al., 2009) distinguishes between Attentional/Cognitive Impulsiveness (easily distracted and has difficulty in controlling thoughts), Motor Im- pulsiveness (acts without thinking and lacks perseverance), and Non-Planning Impulsiveness (fails to make plans and is bored by cognitive complexity). The latter two scales correspond broadly to response disinhibition and short time horizon. A recent psycho- metric evaluation indicated no sex differences on any of the scales (Stanford et al., 2009).

Whiteside and Lynam (2001) included many existing impulsiv- ity scales (as well as the Big Five personality traits) in a factor analysis from which they derived their four UPPS measures. UPPS is the acronym for the four subscales of this measure: Urgency, (lack of) Premeditation, (lack of) Perseverance, and Sensation Seeking. Lack of Premeditation (a failure to delay action in order to think or plan) incorporates the components of response disin- hibition and time horizons. Lack of Perseverance captures poor self-discipline resulting in an inability to resist boredom and re- main with a task until completion. Urgency is the tendency to act rashly when experiencing strong negative affect. Their fourth subscale, Sensation Seeking, is considered separately under sensation-seeking measures.

Dickman’s (1990) Dysfunctional Impulsivity scale reflects fail- ure of deliberation and response inhibition, and we consider it as a subtype of impulsivity. We treat the Functional Impulsivity scale as a measure of sensation seeking, as discussed earlier.

Other measures of impulsivity are factors or scales taken from global personality inventories. Tellegen’s (1982) MPQ contains a facet scale of Control Versus Impulsiveness. We include this facet in preference to the higher order factor of Constraint, which aggregates Control Versus Impulsiveness with Harm Avoidance and Traditionalism. We also include the Impulsivity/Carelessness Style scale from the Social Problem-Solving Inventory (D’Zurilla, Nezu, & Maydeu-Olivares, 1996).

In the NEO Personality Inventory–Revised, Costa and McCrae (1992) identified three forms of impulsivity. They employed the termimpulsivenessnarrowly for a facet of Neuroticism defined as the “inability to control cravings and urges” (suggesting common- ality with Whiteside and Lynam’s Urgency scale). Women score significantly higher than men, with effect sizes of 0.23 in the United States and 0.11 in other cultures (Costa et al., 2001). The authors explicitly noted that this facet “should not be confused with spontaneity, risk taking or rapid decision time” (Costa & McCrae, 1992, p. 16). This last quality, which corresponds more closely with other researchers’ definitions, appears to be measured by Deliberation (“the tendency to think carefully before acting”; p.

18) and perhaps by Self-Discipline (“the ability to begin tasks and carry them through to completion despite boredom and other distractions”; p. 18). Both of these are facets of Conscientiousness, and sex differences are nonsignificant on both scales (Costa et al., 2001).

Despite these distinctions between subtypes, there is consider- able similarity between items that belong to different scales andload on different factors. Consider, for example, two items: “I am a steady thinker” and “I am a careful thinker.” Both are from the BIS-11, but the first assesses attentional impulsiveness and the second motor impulsiveness. The following three items again seem to have similar meanings but come from different scales and inventories: “I have trouble controlling my impulses” (UPPS Ur- gency), “I act on impulse” (BIS Motor Impulsiveness), and “I often make up my mind without taking the time to consider the situation from all angles” (Dickman Dysfunctional Impulsivity).

The various scales include a mixture of items reflecting poor inhibition of behavior, overly fast decision making, restlessness, inattention, low anxiety, and failure of long-term planning. Many rely on general statements such as “I am an impulsive person,” for which respondents must effectively employ their own understand- ing of impulsivity to formulate an answer.

In studies in which both psychometric and behavioral measures are employed, weak or nonsignificant correlation between them are typically reported (Crean, de Wit, & Richards, 2000; Gerbing, Ahadi, & Patton, 1987; Helmers, Young, & Pihl, 1995; Lane et al., 2003; Malle & Neubauer, 1991; Milich & Kramer, 1984; S. H.

Mitchell, 1999; Paulsen & Johnson, 1980; Reynolds, Ortengren, et al., 2006; Reynolds et al., 2008; Reynolds, Richards, & de Wit, 2006; White et al., 1994). Those significant correlations that do emerge are not consistently between measures on which congru- ence would be expected (Kirby, Petry, & Bickel, 1999; Mobini, Grant, Kass, & Yeomans, 2007; Swann, Bjork, Moeller, & Dough- erty, 2002). Overview of the Study As the preceding discussion indicates, there is a wide range of measures designed to assess impulsivity based on disparate theo- retical approaches and operationalizations. A researcher wishing to use impulsivity as an explanatory variable might use any one of these, depending on his or her definition of impulsivity and the reason for wanting to measure it. Part of the aim of the present analysis was to demonstrate the variety of ways that psychologists measure impulsivity and to examine the extent to which significant sex differences depend upon the choice of measure and conceptual approach. We therefore begin our analysis by computing effect sizes separately for each measure of impulsivity. Following this, we group the measures into domains based on differences in the conceptualization and measurement of impulsivity.

Six Domains of Impulsivity Measurement We group the measures into the following six domains (see Table 1 for an overview): (a) reward sensitivity, (b) punishment sensitivity, (c) sensation seeking and risk taking, (d) general im- pulsivity (e) specific forms of impulsivity, and (f) behavioral measures of impulsivity. What follows is a brief outline of each domain.

Reward sensitivity and punishment sensitivity are included as distinct domains to address the suggestion that impulsivity might be explained by oversensitivity to reward or by deficiencies in sensitivity to punishment. Sensation seeking and risk taking mea- sures are distinguishable from impulsivity measures by their greater emphasis on risk, sensation, and danger than on the im- 106 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. pulsiveness of the action. Such inventories clearly identify them- selves as concerned with sensation seeking or subtypes thereof.

General impulsivity includes inventories that pose questions at a general level (e.g., “I am an impulsive person”) rather than spec- ifying contexts or distinguishing psychological functions. Impul- sivity is generally assessed here as a global construct as opposed to subtypes (e.g., motor impulsiveness). Studies reporting total scores derived from summing or averaging specific subscales are ana- lyzed here. The domain of specific forms of impulsivity assesses impulsivity in specific psychological processes or contexts. Spe- cific measures stem from factor-analytic studies indicating that impulsivity is multidimensional. (Note that UPPS Sensation Seek- ing and Dickman Functional Impulsivity are included in the sensation-seeking category rather than specific forms.) Finally, behavioral measures of impulsivity are included as a separate domain to maintain the distinction between psychometric self- report measures and behavioral tasks. This domain includes exec- utive response inhibition tasks (e.g., the Stop Signal task), visual– cognitive tasks (e.g., the Matching Familiar Figures Test), the IGT, Delay Discounting, and the BART (for a description of these tasks, see Table 2).

Hypothesized Sex Differences Men are expected to score higher on sensation-seeking and risk-taking measures. At an evolutionary level, this expectation derives from men’s lower parental investment and the consequent reproductive benefits associated with risk taking in the service of mate competition and hunting. This sex difference, to the extent that it derives from an evolved module, is likely to occur at a motivational level and to be resistant to conscious or strategic control (MacDonald, 2008). Most theorists attribute men’s greater sensation seeking to a strong appetitive motivation and thus predict that men should demonstrate higher BAS or sensitivity to reward than women. We therefore predict a male advantage on measures of reward sensitivity. However, Campbell (1999, 2002) argued from an evolutionary perspective that women’s aversion to sensa- tion seeking results from their lower threshold for experiencing fear. Similarly, Cloninger (1987), from a proximal genetic and neurochemical basis, argued for greater harm avoidance by women. Women’s higher levels of anxiety and depression suggest a greater sensitivity to threatening stimuli. We expect this to be reflected in higher BIS and sensitivity to punishment scores among women. We therefore predict a female advantage on measures of punishment sensitivity.

Effortful control is represented in three of our measurement domains: general impulsivity, specific forms of impulsivity, and behavioral measures of impulsivity. Developmental studies have shown a large effect size favoring girls for effortful control (Else- Quest et al., 2006), and in their narrative review, Bjorklund and Kipp (1996) claimed a female advantage in social and behavioral tasks in line with their evolutionary hypothesis. Several research- ers have proposed that the greater strength of male drives makes them harder to hold in check (MacDonald, 2008; Zuckerman, 1994). All of this evidence suggests that effortful control will be stronger in women than in men.

When we consider effortful control conceptualizations of im- pulsivity, however, sex differences are likely to depend on the inventory or task used (Costa et al., 2001; Feingold, 1994; McCraeet al., 2005). Different behavioral measures appear to assess quite different components of impulsivity, ranging from errors in spatial navigation to a tendency to favor immediate over delayed reward.

Psychometrically measured specific forms of impulsivity also cover a broad range of behaviors, from an inability to resist food when depressed to a tendency not to plan tasks carefully. Further- more, the general wording of some general impulsivity measures (e.g., “I act on impulse”) may result in men’s and women’s tending spontaneously to think of different sex-typical contexts. This ten- dency would diminish the power to detect consistent sex differ- ences. Therefore, although we tentatively predict that women will demonstrate greater effortful control than men, we expect consid- erable inconsistency in the domains of behavioral measures and specific forms of impulsivity and only a modest effect of sex on general measures. Variance Ratios In addition to examining sex differences in central tendency, we computed male:female variance ratios for different measures of impulsivity. A male-biased variance ratio has been found for a number of physical and psychological traits (Hedges & Nowell, 1995; Lehre, Lehre, Laake, & Danbolt, 2009). From an evolution- ary perspective, Archer and Mehdikhani (2003) proposed that men are freer than women to vary in their levels of parental investment, giving rise to greater male variability on sexually selected traits.

Their analysis bore this out for measures of physical aggression and mate choice. The present data afford the opportunity to extend this proposal of greater male variance, as well as a higher male mean, for impulsivity—a trait that has also been argued to be sexually selected (Daly & Wilson, 1988). Method Sample of Studies The initial search was conducted with the database PsycINFO, which has a broad coverage of psychology and social science journals as well as unpublished dissertations. Search terms in- cluded the keywordsimpulsivityandimpulsivenessbut notsexor genderin order to prevent selection bias. Specific inventories were not subject to search, because the aim was to identify the range of measures used for assessing impulsivity. This was especially im- portant due to historic variations in the conceptualization and operationalization of this concept. The following search limits were imposed: (a) human populations only, (b) English language only, (c) male and female populations, (d) age groups above the age of 10, and (e) articles published between 1980 and 2008. The search yielded 3,156 abstracts.

Abstracts were screened, and any articles failing to meet the following criteria were removed: (a) the study was empirical, (b) the sample included a minimum of 10 men and 10 women, (c) data from normative samples were reported (defined as samples with no specified a priori selection factors regarding traits or behaviors; for example, samples of individuals with alcoholism or children of individuals with alcoholism were excluded, whereas studies of the drinking habits of normative student populations were included; where clinical studies were examined, data were recorded only from normative control groups), (d) self-reported psychometric 107 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. and/or behavioral measures were used, (e) impulsivity was mea- sured as an independent construct (for instance, some common attention-deficit/hyperactivity disorder checklists amalgamate hy- peractivity and impulsivity into a single dimension and report a single combined measure; such scales were excluded), and (f) data were presented or potentially available from which a sex differ- ence could be calculated. Where abstracts did not provide suffi- cient information to establish whether they met the inclusion criteria, they were included in the next stage of the selection process.

One thousand and sixty-five articles were downloaded or re- quested through interlibrary loan, and 70 unpublished dissertations were downloaded via the ProQuest database. If an article met the inclusion criteria but lacked sufficient data for an effect size to be computed, authors were contacted by e-mail if the article had been published within the last 5 years. Two hundred and three such requests were made with 75 usable responses. In 12 cases, authors provided additional data from studies not identified in the initial search.

Ultimately, 244 articles and 33 unpublished studies were in- cluded in the meta-analysis, giving a total of 277 studies with 310 samples. From these, 741dvalues were calculated (see supple- mental materials in conjunction with the references for a listing of all studies included in the analysis).

Coding the Studies For each study, the following information was coded: (a) all statistics relevant to the magnitude of the sex difference (means, standard deviations, correlations,tandFtests), (b) the number of male and female participants, (c) the measures of impulsivity employed in the study, (d) the population studied (university, community, schools or colleges), (e) the age of the sample (mean, standard deviation, or range), (f) the nationality of the sample, (g) the publication status of the study, and (h) the sex of the first author. The coding of categorical variables was undertaken by two coders. Cohen’s kappa was calculated as a measure of interrater agreement and ranged from .83 (age) to 1.00 (publication status).

Discrepancies were checked and resolved by agreement between the two coders. Across all measures, 741 effect sizes were ana- lyzed, with a total sample size of 149,496 participants from 27 countries (see Table 3).

Grouping by Category and Domain Effect sizes were grouped into 40 measurement categories (see Table 1). Of these, 35 represented established measures. Some studies, however, used measures created specifically for their study, unpublished measures, or measures that did not appear more than twice in the whole sample of studies. These were placed into one of five general categories: general impulsivity other measures, sensation seeking other measures, risk taking, impulse control, and visual– cognitive tasks.

Measures were also grouped into six domains of impulsivity, as outlined in the introduction (see Table 1). Given the lack of consensus about the dimensionality and conceptualization of im- pulsivity, some researchers may disagree with these groupings.

Results are therefore presented to allow examination both on a category-by-category basis and by domain. Statistical Analysis Statistical independence.The requirement of independence of observations means that the same sample could not be included multiple times when computing an aggregate effect size. Many studies used multiple measures of impulsivity. Aggregating studies by measure does not violate this requirement of independence.

However, in the domain-level analysis, where multiple measures from a sample were grouped in the same domain, the mean of the dvalues for the measures was included. Effect sizes and variance ratios were calculated for all categories and domains.

Mean-difference effect sizes.Formulae for calculating effect sizes were taken from Lipsey and Wilson (2001). For reported measures, Cohen’sdwas calculated (by dividing the difference between male and female means by an estimate of the pooled standard deviation):

d x male x female SD pooled .

Four effect sizes were reported by the authors. Wheredvalues were not reported,dwas calculated either by converting existing parametric statistics such asF(15 effect sizes),t(12 effect sizes), andrvalues (72 effect sizes) or directly from published or provided means and stan- dard deviations (559 effect sizes). Seventy-nine values were estimated Table 3 Summary Statistics for All Samples Included in the Analysis CategorykN Male Female Age (years) 11–15 34 13,215 14,032 15–18 42 21,395 22,333 18–21 84 12,492 18,856 21–30 76 8,964 11,516 30–40 29 5,239 7,489 40 19 3,605 4,050 Age not specified or wide age range 26 2,911 3,400 Geographical area United States Canada, and Central America 184 41,467 46,807 United Kingdom, Europe, Australia, and New Zealand 115 23,525 31,838 Asia, Africa, and Middle East 11 2,830 3,030 Population Schools (up to age 18) 51 29,264 30,019 University/college students 147 17,203 27,107 Community 89 16,073 18,388 Mixed or not specified 23 5,282 6,162 Publication status Published 275 61,220 74,898 Unpublished 35 6,601 6,777 Domain General measures of impulsivity 206 50,805 62,428 Specific measures of impulsivity 62 7,873 10,891 Sensation seeking and risk taking 130 23,402 28,914 Reward sensitivity 18 2,380 3,598 Punishment sensitivity 19 2,698 4,212 Behavioral measures 50 3,746 3,753 Grand total a 310 67,821 81,675 aObtained by summing the total number of participants for all 310 samples. 108 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. as zero where nonsignificant gender differences were reported but no relevant statistics could be located. In the Results section, summary effect sizes including and excluding these conservatively estimatedd values are reported. Following convention, female means were sub- tracted from male means so that positivedvalues represent higher male than female scores.

Outliers, heterogeneity, and moderator analysis.Outliers were identified on a category-by-category basis as follows. Cases in which the effect size was estimated as zero due to insufficient data were removed. For the remainingdvalues,zscores were calculated. Values ofdwithzscores outside the range of 2.5 and 2.5 were classified as outliers and subsequently removed from analysis. Results are reported both including and omitting outliers.

The heterogeneity statistic,Q, was calculated for each analysis.

Qstatistics test for equality of effect sizes within each analysis and follow a chi-square distribution withk 1 degrees of freedom (Hedges & Olkin, 1985). A simplified formula is as follows:

Q i 1 k w d i d 2, wherew 1/v,v (N male N female )/N total d 2/2(N total ), andk is the number of effect sizes.

SignificantQstatistics are indicative of the presence of a non- heterogeneous dispersion between effect sizes but not its magni- tude.Qcan be sensitive to sample size (Hardy & Thompson, 1998; Higgins & Thompson, 2002), and its significance is expected when analyzing considerable numbers of studies (Higgins, 2008). Het- erogeneity is incorporated into estimates of effect size via random- effects models.

Random-effects model.Random-effects models make the assumption that the variation between studies is attributable not only to sampling differences between studies but also to other, unspecified influences within studies. It assumes effect size pa- rameters to be randomly sampled and estimates these parameters based on the population (but see Schulze, 2004). The random- effects model is particularly appropriate when effect sizes are significantly heterogeneous. The conceptual background of this study suggested that heterogeneity within the various measures and domains was likely, and so a random-effects model was implemented a priori.

Moderator analyses were performed for each measure, in order to explore study variables potentially accounting for variability in effect sizes. SignificantQstatistics were not considered prerequi- sites for conducting a moderator analysis (see Rosenthal & DiMatteo, 2001). The moderator variables tested were as follows:

age (grouped by mean age into six levels: 10 –15 years, 15–18 years, 18 –21 years, 21–30 years, 30 – 40 years, 40 years and over), population (grouped into three categories: university students, community samples, school samples), geographical area (grouped into three categories: United States, Canada, and Central America; United Kingdom, Europe, Australia, and New Zealand; Asia, Africa, and the Middle East), sex of first author, and publication status of the study. The test statistic for the moderator analysis is Q B, which is analogous to theFstatistic in analysis of variance (Hedges & Pigott, 2004). A significantQ Bdenotes that the effect sizes for the different subgroups in the analysis differ significantly.

Variance ratios.Untransformed variance ratios were calcu- lated wherever sufficient data were available, resulting in 475values. Ratios were computed by dividing the male variance by the female variance. Greater male than female variability is therefore reflected in values greater than 1. In keeping with previous authors (Else-Quest et al., 2006), ratios were transformed via base-10 log before calculating category means.

Publication bias.In many of the studies retrieved for this meta-analysis, sex was not a variable of interest, making publication bias less likely. Nevertheless, the possibility of publication bias was explored where possible. Two methods were employed. First, a mod- erator analysis was run to determine if effect sizes for published studies significantly differed from unpublished studies. Second, fol- lowing Begg and Mazumdar (1994), the rank correlation between standard error (largely a function of sample size) and effect size for studies within domains was calculated. This is a statistical analogue of a funnel plot. Because the assessment of publication bias by any means is unreliable where the number of studies is small (Borenstein, Hedges, Higgins, & Rothstein, 2009), this test was implemented only for categories with at least 20 studies.

Statistical software.Thedvalues andQstatistics were calculated with SPSS, and the random-effects models, moderator analyses, and tests for publication bias were run with Comprehen- sive Meta-Analysis Version 2 (Borenstein, Hedges, Higgins, & Rothstein, 2005). Results Tables 4 –7 report effect sizes by measure and associated sta- tistics, as well as the overall effect size for the impulsivity domains to which they have been assigned: reward sensitivity, punishment sensitivity, sensation seeking and risk taking, and general impul- sivity. We did not aggregate the results from specific forms of impulsivity and behavioral measures of impulsivity because, in these domains, aggregation would violate the distinctiveness of the measures. Results from these domains are presented in Tables 8 and 9, respectively. For a complete list of effect sizes and variance ratios for all studies, see the supplemental materials. The supple- mental materials also identify the authors of the study, the number of male and female participants, moderator variables coded (age, population, geographical area, sex of first author, published or unpublished source), and the impulsivity measures used.

Table 10 shows the significant moderator variables for each measure. All moderators significant atp .05 are reported in these tables, but because of the large number of analyses con- ducted and the consequent inflated likelihood of Type I errors, only those that were significant atp .01 are discussed in the text.

We also restrict our discussion of significant variance ratios to those wherep .01.

Reward Sensitivity Overall effect sizes.For the domain general analysis, there were 18 effect sizes, all but one of which were computed (see Table 4). The overall effect size was negligible and nonsignificant (d 0.01). However, there was marked variation in the direction and magnitude of effect sizes for specific measures.

The effect size for the BAS total score was nonsignificant but slightly favored women (d 0.13). This was chiefly due to women’s significantly higher scores on the BAS Reward subscale (d 0.27). The BAS Reward scale poses questions about 109 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. emotional responsiveness (e.g., “When good things happen to me, it affects me strongly”). Women outscored men even more strongly on the TCI scale of Reward Dependence (d 0.56).

This scale, despite its name, is composed of subscales specifically assessing “sentimentality, social sensitivity, attachment, and de- pendence on approval by others” (Center for Well-Being, n.d., “What does the TCI measure?” para. 6). These are areas where past research suggests women should score highly (Cross & Mad- son, 1997).

The female advantage on these scales stands in contrast to the sex difference favoring men on the SPSRQ and GRAPES Reward scales (d 0.44). These latter two scales contain many items that oriented to competitive success and ambition (e.g., SPSRQ: “Are you interested in money to the point of being able to do risky jobs?”; GRAPES: “I expect that I will rise to the top of any field of work I am or will be engaging in”). Thus there appeared to be differences in the conceptualization and contextualization of re- ward that are potentially confounded with masculinity and femi- ninity.

The remaining two BAS scales, Drive (d 0.06) and Fun (d 0.08), yielded nonsignificant sex differences. Again, this null result might be related to the way in which the constructs are operationalized. Although the Drive scale appears to have an appetitive component reflecting ambition, it differs from the SPSRQ in that it does not refer specifically to money or status.

Instead, the item wording is again very general (e.g., “I go out of my way to get things I want”). The Fun scale contains items that appear to tap impulsivity (e.g., “I often act on the spur of the moment”). It is therefore perhaps unsurprising that the modest effect sizes on these two scales were in line with that found for the domain of general impulsivity (see Measures of General Impul- sivity).Moderator analysis.Only the BAS total and the BAS Re- ward scale showed significant heterogeneity. Moderator analyses were performed on all measures (see Table 10). Only one was significant atp .01: Age moderated the sex difference in BAS Reward, with a smaller sex difference for samples aged 18 –21 years (d 0.16) than for the 21–30 age group (d 0.54).

Variance ratios.Mean antilog variance ratios can be found in Table 4. None are significantly different from 1. Punishment Sensitivity Overall effect sizes.For the domain general analysis, there were 18 independent effect sizes, all but one of which were computed (see Table 5). There was a significant, small to moderate effect size favoring women (d 0.33), although, once again, there was variation in the magnitude as a function of the measure used.

All three measures showed a difference in favor of women, two of which were significant. TCI Harm Avoidance (d 0.43) assesses feelings of anxiety in unpredictable situations (e.g., “Usu- ally I am more worried than most people that something might go wrong in the future”). The gist of the item content is very similar to that of the BIS, on which there was a moderate to large sex difference (d 0.63). BIS items are also concerned with anxiety in the face of failure (e.g., “I feel worried when I think I have done poorly at something important,” “If I think something unpleasant is going to happen, I usually get pretty ‘worked up’”). Both TCI Harm Avoidance and the BIS therefore assess emotional responses to actual or anticipated punishment.

The aggregated effect size for SPSRQ and GRAPES mea- sures was again in the female direction but only approached significance (d 0.12). Many of the GRAPES items appear Table 4 Sex Differences in Measures of Reward Sensitivity Measured95% CI kN QVR (k ) LL ULMen Women SPSRQ and GRAPES All studies 0.42 0.33 0.52 9 1,091 2,443 13.57 1.05 (9) Computed only a 0.44 0.36 0.53 8 1,068 2,358 9.83 1.05 (9) TPQ–TCI Reward Dependence All studies 0.56 0.68 0.44 4 437 841 2.22 1.08 (4) BAS Total All studies 0.13 0.38 0.12 4 420 537 9.13 0.80 (4) BAS Drive All studies 0.06 0.04 0.15 9 1,201 1,372 9.19 0.96 (9) BAS Fun All studies 0.08 0.01 0.17 9 1,201 1,372 8.71 1.08 (9) BAS Reward All studies 0.27 0.41 0.13 9 1,201 1,372 19.35 0.95 (9) Total of reward sensitivity measures All studies 0.01 0.17 0.19 18 2,380 3,598 340.90 1.03 (44) Computed only a 0.01 0.18 0.20 17 2,357 3,513 340.86 1.03 (44) Note.Effect sizes are in the male direction if positive and in the female direction if negative. CI confidence interval;LL lower limit;UL upper limit;Q homogeneity statistic; VR (k ) mean variance ratio (number of sample sizes from which variance ratios could be calculated); SPSRQ Sensitivity to Reward and Sensitivity to Punishment Questionnaire; GRAPES Generalized Reward and Punishment Expectancy Scales; TPQ–TCI Tridimensional Personality Questionnaire–Temperament and Character Inventory; BAS Behavioral Activation System. aRemoved: A´ vila & Parcet (2000). p .05. p .001. 110 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. to tap pessimism and anticipatory worry in a similar way to the above scales (e.g., “When there is a disease going around, I worry about getting it,” “In light of all the crime in the world, I expect to be the victim of a mugging or an assault at some point during my life”). However the SPSRQ items seem to capture social assertiveness versus shyness (e.g., “Would you be bothered if you had to return to a store when you noticed you were given the wrong change?” “Do you generally avoid speak- ing in public?”). The content therefore appears to be more associated with extraversion–introversion, on which we would not expect a marked sex difference (Costa et al., 2001; Schmitt, Realo, Voracek, & Allik, 2008).

Moderator analysis.Only the effect sizes for punishment sensitivity as measured by the SPSRQ and GRAPES scales showed significant heterogeneity. Moderator analyses were per- formed on all categories. Age moderated the sex difference on the BAS Reward scale, such that the sex difference was more pro- nounced in the 21–30 age group (d 0.54) than the 18 –21 age group (d 0.16).

Variance ratios.Mean antilog variance ratios can be found in Table 5. None are significantly different from 1.

Sensation Seeking and Risk Taking Overall effect sizes.Table 6 reports effect sizes for the aggregated domain of sensation seeking and risk taking and the 13 measures it subsumes. For the domain general analysis, there were 130 independent effect sizes, of which five were estimated as zero.

Thedvalues for MPQ Harm Avoidance were reverse-scored before being combined with the other measures in this domain.

The overall effect size was small to moderate in size, with signif- icantly higher sensation seeking and risk taking among men (d 0.41).

For the measures subsumed in this domain, 10 of the 13 mea- sures had significant sex differences, and all reflected greater sensation seeking by men. The largest effect size was for MPQ and Personality Research Form (PRF; Jackson, 1994) measures ofHarm Avoidance (d 0.78). The MPQ Harm Avoidance ques- tionnaire offers respondents a choice between two somewhat aver- sive activities from which they select the one that they would like to undertake less (e.g., “Having to walk around all day on a blistered foot” or “Sleeping out on a camping trip in an area where there are rattlesnakes”). High scorers prefer safer activities even if they are tedious and do not enjoy the excitement of adventure (Tellegen, 1982). This scale appeared to magnify the sex differ- ences found on the similarly structured SSS Thrill and Adventure, which differs in offering a positive choice between two alterna- tives (e.g., “I would like to try surfboard riding” or “I would not like to try surfboard riding”).

Four of the measures showed moderate sex differences includ- ing I 7Venturesomeness (d 0.51), SSS Total (d 0.50), SSS Disinhibition (d 0.57), SSS Thrill and Adventure Seeking (d 0.41), and UPPS Sensation Seeking (d 0.49). Slightly lower effect sizes were found for Risk Taking (d 0.38), Dickman Functional Impulsivity (d 0.24), and Sensation Seeking Other Measures (d 0.22). The ZKPQ ImpSS scale includes items separately assessing impulsivity and sensation seeking, and the effect size of 0.19 was nonsignificant with high heterogeneity (based on four studies). The two scales measuring intolerance of monotony showed small effect sizes: SSS Boredom Susceptibility (d 0.20) and KSP Monotony Avoidance (d 0.15). SSS Experience Seeking, which captures a desire for novel but safe activities, showed a nonsignificant effect size of 0.01. This pro- vides more evidence that risk taking per se produces sex differ- ences.

Moderator analysis.For most of the measures within the domain of sensation seeking and risk taking, there was significant heterogeneity. The exceptions were SSS Total, Risk Taking, KSP Monotony Avoidance, and MPQ–PRF Harm Avoidance. Moder- ator analyses were performed for all measures (see Table 10).

The sex difference on Eysenck’s I 7Venturesomeness scale appears to be moderated by age. With the exception of a small number of samples aged 30 – 40 years (d 0.84), the largest effect Table 5 Sex Differences in Measures of Punishment Sensitivity Categoryd95% CI kN QVR (k ) LL ULMen Women SPSRQ and GRAPES All studies 0.11 0.23 0.00 9 1,136 2,563 18.50 0.97 (9) Computed only a 0.12 0.24 0.01 8 1,113 2,478 18.31 0.97 (9) TPQ–TCI Harm Avoidance All studies 0.43 0.52 0.33 5 784 1,391 4.43 1.08 (4) BIS All studies 0.63 0.74 0.52 8 1,026 1,197 8.65 1.14 (8) Total of punishment sensitivity measures All studies 0.32 0.45 0.19 18 2,598 4,091 119.46 1.05 (21) Computed only a 0.33 0.47 0.20 17 2,575 4,006 117.63 1.05 (21) Note.Effect sizes are in the male direction if positive and in the female direction if negative. CI confidence interval;LL lower limit;UL upper limit;Q homogeneity statistic; VR (k ) mean variance ratio (number of sample sizes from which variance ratios could be calculated); SPSRQ Sensitivity to Reward and Sensitivity to Punishment Questionnaire; GRAPES Generalized Reward and Punishment Expectancy Scales; TPQ–TCI Tridimensional Personality Questionnaire–Temperament and Character Inventory; BIS Behavioral Inhibition System. aRemoved: A´ vila & Parcet (2000). p .05. p .001. 111 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. sizes are present in the 15–18 (d 0.63) and 18 –21 (d 0.54) age groups, with effect sizes in the other age groups ranging from 0.37 to 0.46. This suggests that, in general, the sex difference in Venturesomeness is largest in young adults. No other moderators were significant in this domain.

Variance ratios.Mean antilog variance ratios can be found in Table 6. Only the variance ratio for SSS Disinhibition is signifi- cantly larger than 1 (p .01), indicating greater male variability on this measure. Overall, there is little evidence for greater male than female variability within this domain. Measures of General Impulsivity Overall effect sizes.Although the domain general effect size (from 206 independent effect sizes, 180 of which were computed) was significant, it was extremely small in magnitude (d 0.08), indicating slightly higher levels of impulsivity in men.

Table 7 shows the mean weighted effect sizes for each of the four measures included in this domain. There was no significant sex difference on Eysenck-based measures of impulsiveness. The KSP Impulsivity scale was also nonsignificant. Although the sex Table 6 Sex Differences in Measures of Sensation Seeking and Risk Taking Measured95% CI kN QVR (k ) LL ULMen Women Eysenck Venturesomeness All studies 0.49 0.43 0.56 49 7,443 10,553 160.99 0.91 (41) Computed only a 0.51 0.44 0.57 47 7,349 10,395 146.80 0.91 (41) Outliers removed b 0.53 0.47 0.59 45 7,267 10,232 118.02 0.91 (39) SSS Total All studies 0.48 0.41 0.56 22 2,563 3,072 31.56 0.95 (17) Computed only c 0.50 0.43 0.56 21 2,541 2,992 27.36 0.95 (17) SSS Thrill and Adventure Seeking All studies 0.41 0.29 0.54 16 2,761 3,498 69.39 0.85 (14) SSS Experience Seeking All studies 0.01 0.11 0.12 10 1,406 2,021 18.27 1.04 (8) Computed only d 0.01 0.11 0.12 9 1,385 1,998 18.27 1.04 (8) SSS Disinhibition All studies 0.52 0.40 0.65 15 2,286 3,007 52.02 1.26 (13) Computed only d 0.54 0.42 0.66 14 2,265 2,984 48.73 1.26 (13) Outliers removed e 0.57 0.46 0.69 13 2,204 2,965 38.93 1.37 (12) SSS Boredom Susceptibility All studies 0.20 0.09 0.31 14 1,922 2,764 36.58 1.07 (11) UPPS Sensation Seeking All studies 0.48 0.33 0.63 15 1,566 2,284 62.44 0.95 (11) Computed only f 0.49 0.34 0.65 14 1,552 2,262 60.39 0.95 (11) Dickman Functional Impulsivity All studies 0.24 0.08 0.39 11 935 1,346 27.59 1.04 (9) ZKPQ Impulsive Sensation Seeking All studies 0.19 0.22 0.60 4 623 706 58.30 1.21 (4) KSP Monotony Avoidance All studies 0.15 0.00 0.29 4 269 510 0.27 0.85 (4) MPQ–PRF Harm Avoidance All studies 0.78 0.92 0.64 3 334 528 0.11 0.91 (3) Risk Taking All studies 0.36 0.29 0.44 11 3,739 3,330 25.66 1.10 (7) Computed only g 0.38 0.31 0.44 10 3,659 3,250 20.00 1.10 (7) Sensation seeking other measures All studies 0.21 0.11 0.30 24 5,694 6,748 236.92 1.08 (23) Computed only h 0.22 0.13 0.32 22 5,432 6,428 229.67 1.08 (23) Total of sensation-seeking measures i All studies 0.39 0.35 0.43 130 23,402 28,914 578.23 0.99 (169) Computed only j 0.41 0.37 0.45 125 22,952 28,334 607.19 0.99 (169) Outliers removed k 0.41 0.37 0.45 123 22,815 28,154 274.42 1.00 (164) Note.Effect sizes are in the male direction if positive and in the female direction if negative. CI confidence interval;LL lower limit;UL upper limit;Q homogeneity statistic; VR (k ) mean variance ratio (number of sample sizes from which variance ratios could be calculated); SSS Sensation Seeking Scale; UPPS Urgency, Premeditation, Perseverance, and Sensation Seeking; ZKPQ Zuckerman–Kuhlman Personality Questionnaire; KSP Karolinska Scales of Personality; MPQ–PRF Multidimensional Personality Questionnaire–Personality Research Form. aRemoved: Leshem & Glicksohn (2007); Reynolds, Ortengren, et al. (2006). bRemoved (in order): Clarke (2004); Rim (1994). cRemoved: Lennings (1991). dRemoved: Lundahl (1995). eRemoved: Curran (2006). fRemoved: Verdejo-Garc ´a et al. (2007). gRemoved: Sahoo (1985). hRemoved:

Lennings (1991); Overman et al. (2004). iIncludes MPQ–PRF Harm Avoidance, reverse scored. jRemoved: Lennings (1991); Leshem & Glicksohn (2007); Lundahl (1995); Overman et al. (2004); Reynolds, Ortengren, et al. (2006); Sahoo (1985); Verdejo-Garc ´a et al. (2007). kRemoved (in order):

Copping (2007); Curran (2006; SSS Experience Seeking and Boredom Susceptibility, ZKPQ Impulsive Sensation Seeking); Lundahl (1995; SSS Thrill and Adventure Seeking); McAlister et al. (2005); Weyers et al. (1995; age 27: Tridimensional Personality Questionnaire–Novelty Seeking). p .05. p .01. p .001. 112 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. differences on the BIS-11 Total (d 0.12) and Impulsivity Other Measures (d 0.13) showed men to be significantly more impul- sive, the effect sizes were again small in magnitude.

Moderator analysis.For all measures within the domain of general impulsivity except the KSP Impulsivity measure, there was significant heterogeneity. Moderator analyses were performed on all measures (see Table 10). Population moderated the sex differ- ence in KSP Impulsivity. The two community samples showed a small but significant sex difference in the female direction (d 0.18), but there was no sex difference in university samples.

Variance ratios.Mean antilog variance ratios can be found in Table 7. None of them are significantly different from 1 atp .01.

Specific Forms of Impulsivity Overall effect sizes.Nine measures of specific forms of impulsivity were analyzed, with a total of 128 independent effect sizes (111 of which were computed) from 56 studies.

Table 8 shows the mean weighted effect sizes for these mea- sures. For most of the measures, there was no sex difference.

There were significant but small sex differences in the maledirection on BIS-11 Cognitive Impulsivity (d 0.13), indicat- ing men’s greater difficulty in concentrating and focusing at- tention; on BIS-11 Non-Planning (d 0.15), suggesting men’s lesser tendency to consider the future; and on Dickman’s Dys- functional Impulsivity (d 0.12), which captures a failure of premeditation resulting in negative consequences. There was a small to moderate effect size on Impulsivity/Carelessness in the Social Problem-Solving Inventory (d 0.32), indicating that men are more likely than women to rush into ill-considered “solutions” to interpersonal problems. There was also a small but significant sex difference in the female direction on UPPS Urgency (d 0.10), indicating that women are more likely to report that their impulse control is disrupted by negative affect or that they feel regret for their impulsive actions. The overall picture is that there are weak, inconsistent sex differences in these specific forms of impulsivity.

Moderator analysis.For most of the specific measures of impulsivity, there was significant heterogeneity in the effect sizes.

The exceptions were UPPS Premeditation, UPPS Urgency, Dick- man Dysfunctional Impulsivity, and the Social Problem-Solving Table 7 Sex Differences in General Measures of Impulsivity Measured95% CI kN QVR (k ) LL ULMen Women Eysenck Impulsiveness All studies 0.03 0.00 0.07 100 14,425 19,680 222.72 1.00 (74) Computed only a 0.04 0.00 0.08 88 13,603 18,768 222.27 1.00 (74) Outliers removed b 0.03 0.01 0.07 82 13,427 18,584 183.63 0.97 (68) BIS Total All studies 0.11 0.05 0.16 58 6,296 8,452 115.14 0.99 (42) Computed only c 0.12 0.06 0.19 48 5,729 7,561 110.68 0.99 (42) Outliers removed d 0.12 0.06 0.18 47 5,702 7,548 105.88 1.01 (41) KSP Impulsivity All studies 0.06 0.19 0.07 7 826 4,452 8.83 0.79 (5) Computed only e 0.06 0.21 0.10 5 789 4,318 8.38 0.79 (5) Impulsivity other measures All studies 0.12 0.07 0.17 54 30,040 31,403 345.60 1.02 (38) Computed only f 0.13 0.08 0.19 47 29,379 30,575 344.99 1.02 (38) Outliers removed g 0.14 0.08 0.19 46 29,354 30,535 338.78 1.02 (38) Total of general impulsivity measures All studies 0.07 0.05 0.10 206 50,805 62,428 244.52 1.00 (159) Computed only h 0.08 0.05 0.11 180 48,862 59,859 359.28 1.00 (159) Outliers removed i 0.08 0.05 0.11 173 48,688 59,683 131.42 0.98 (153) Note.Effect sizes are in the male direction if positive and in the female direction if negative. CI confidence interval;LL lower limit;UL upper limit;Q homogeneity statistic; VR (k ) mean variance ratio (number of sample sizes from which variance ratios could be calculated); BIS Barratt Impulsiveness Scale; KSP Karolinska Scales of Personality. aRemoved: Allen et al. (1998); Brown et al. (2006); Deffenbacher et al. (2003); Doran et al. (2007); Keilp et al. (2005); Ketzenberger & Forrest (2000); Leshem & Glicksohn (2007); Reynolds, Ortengren, et al. (2006); Reynolds et al. (2007); van den Broek et al. (1992). bRemoved (in order): Weyers et al. (1995; age 50); Saklofske & Eysenck (1983; age 15); Weller (2001); Starrett (1983; senior high); Corr et al. (1995); Lopez Viets (2001). cRemoved:

Allen et al. (1998); Chung & Martin (2002); Dinn et al. (2002); Hulsey (2001); Jack & Ronan (1998); Leshem & Glicksohn (2007); Nagoshi et al. (1994); Neubauer (1992); Patock-Peckham et al. (1998); Reynolds, Ortengren, et al. (2006); Rigby et al. (1992); van den Broek et al. (1992). dRemoved: Clark et al. (2005). eRemoved: Lennings (1991); Lennings & Burns (1998). fRemoved: Allen et al. (1998); Bembenutty & Karabenick (1998); McMahon & Washburn (2003); Overman et al. (2004); Plouffe & Grawelle (1989); Ryff & Heincke (1983); Schweizer (2002). gRemoved: Malle & Neubauer (1991). hRemoved: Allen et al. (1998); Bembenutty & Karabenick (1998); Brown et al. (2006); Chung & Martin (2002); Deffenbacher et al. (2003); Dinn et al. (2002); Doran et al. (2007); Hulsey (2001); Jack & Ronan (1998); Keilp et al. (2005); Ketzenberger & Forrest (2000); Lennings (1991); Lennings & Burns (1998); Leshem & Glicksohn (2007); McMahon & Washburn (2003); Nagoshi et al. (1994); Neubauer (1992); Overman et al. (2004); Patock-Peckham et al. (1998); Plouffe & Grawelle (1989); Reynolds, Ortengren, et al. (2006); Reynolds et al. (2007); Rigby et al. (1992); Ryff & Heincke (1983); Schweizer (2002); van den Broek et al. (1992). iRemoved (in order): Weyers et al. (1995; 50-year-olds); Clark et al. (2005); Saklofske & Eysenck (1983; 15-year-olds); Malle & Neubauer (1991); Weller (2001); Starrett (1983: senior high sample); Corr et al. (1995). p .05. p .01. p .001. 113 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Inventory. Moderator analyses were performed for all measures.

Table 10 presents those categorical variables that were found to have a significant moderating effect on the sex difference.

The sex difference in BIS Non-Planning was moderated by geographical area, with samples from the United States, Canada, and Central America showing a moderate sex difference in the male direction (d 0.30) and samples from the United Kingdom, Europe, Australia, and New Zealand showing no sex difference.

The sex difference in UPPS Perseverance was moderated by age:

The sex difference in the male direction appears only in samples aged over 21 (d 0.38). In UPPS Urgency, age also moderated the magnitude of the sex difference in an inconsistent fashion. Here an effect size in favor of women was confined to the age 15–18 age group (d 0.31). The significant moderation by population sampled may be an artifact of this age effect; the effect size was significant and in the female direction for the school samples (d 0.26), but not for undergraduate samples.

The sex difference in Impulse Control also appears to be mod- erated by age but in an inconsistent fashion. The two samples aged 15–18 show roughly equal sex differences in opposite directions, resulting in an overall null result; samples aged 18 –21 show a sex difference in the male direction (d 0.40); whereas samples aged over 21 show a small sex difference in the female direction (d 0.17). Geographical area also appears to moderate the sex dif- ference in impulse control: The two samples from the United Kingdom, Europe, Australia, and New Zealand show a substantialsex difference in the female direction (d 0.55), whereas those from the United States, Canada, and Central America show a small sex difference in the male direction (d 0.17).

Variance ratios.Mean antilog variance ratios can be found in Table 8. None were significantly different from 1. Behavioral Measures of Impulsivity Overall effect sizes.The 48 studies in behavioral measures of impulsivity produced 64 independent effect sizes, of which 43 were computed. Effect sizes are presented in Table 9. A significant sex difference, moderate in size and in the male direction, was found on the BART (d 0.36). This suggests that men are willing to continue the pursuit of a reward in the face of increasing risk for a longer time than women. Because the BART is a measure of risk taking, it is not surprising that the significant sex difference is consistent with those found in the general domain of sensation seeking and risk taking.

On the IGT, men were found to perform significantly better (i.e., less impulsively) than women (d 0.34). This finding is in contradiction to developmental and evolutionary predictions relat- ing to effortful control, suggesting that women are less able than men to resist a monetary reward in the short term in order to avoid a greater monetary loss later. However, it should be noted that the IGT was not designed to assess impulsivity but decision making.

Bechara, Damasio, Damasio, and Anderson (1994, p. 8) noted that Table 8 Sex Differences in Measures of Specific Forms of Impulsivity Categoryd95% CI kN QVR (k ) LL ULMen Women BIS Cognitive All studies 0.13 0.00 0.26 18 1,776 2,372 56.79 0.92 (16) BIS Motor All studies 0.08 0.00 0.17 19 2,990 3,620 34.09 1.04 (13) BIS Non-Planning All studies 0.15 0.06 0.24 20 3,187 3,839 43.31 0.96 (17) UPPS Perseverance All studies 0.05 0.07 0.17 14 1,449 2,111 34.27 0.93 (12) Computed only a 0.05 0.08 0.17 13 1,435 2,089 34.26 0.93 (12) UPPS Premeditation All studies 0.01 0.08 0.06 14 1,449 2,111 7.77 1.06 (12) Computed only a 0.01 0.08 0.06 13 1,435 2,089 7.77 1.06 (12) Outliers removed b 0.00 0.07 0.07 12 1,423 2,031 3.40 1.00 (11) UPPS Urgency All studies 0.10 0.19 0.01 14 1,449 2,111 19.15 0.94 (12) Computed only a 0.10 0.19 0.01 13 1,435 2,089 19.06 0.94 (12) Dickman Dysfunctional Impulsivity All studies 0.12 0.02 0.23 12 1,107 1,518 16.58 0.91 (10) Impulse Control All studies 0.02 0.22 0.25 11 1,303 1,767 92.15 0.85 (9) Computed only c 0.02 0.23 0.26 10 1,277 1,743 92.09 0.85 (9) Social Problem-Solving Inventory All studies 0.23 0.09 0.37 6 990 1,850 11.37 1.05 (5) Computed only d 0.32 0.23 0.41 5 869 1,199 2.80 1.05 (5) Note.Effect sizes are in the male direction if positive and in the female direction if negative. CI confidence interval;LL lower limit;UL upper limit;Q homogeneity statistic; VR (k ) mean variance ratio (number of sample sizes from which variance ratios could be calculated); BIS Barratt Impulsiveness Scale; UPPS Urgency, Premeditation, Perseverance, and Sensation Seeking. aRemoved: Verdejo-Garc ´a et al. (2007). bRemoved: Anestis et al. (2007). cRemoved: Fox et al. (2007). dRemoved: Maydeu-Olivares et al. (2000). p .05. p .01. p .001. 114 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. a patient who performed poorly on the IGT due to damage to the prefrontal cortex was “not perseverative, nor is he impulsive.” Men’s superior performance on this task may actually be the consequence of women’s greater punishment sensitivity: There is evidence that women prefer an IGT strategy that minimizes the frequency of punishment, even though this may be disadvanta- geous in the long run (Goudriaan, Grekin, & Sher, 2007). This argument raises questions about the validity of attributing poor performance on this task uniquely to impulsivity. Delay discount- ing, also used as a measure of the propensity to resist small short-term rewards as part of a long-term strategy, showed no sex difference. Although this result is consistent with our finding that general measures of impulsivity did not differ between the sexes, we note that delay discounting measures only one of the many facets thought to be subsumed by the construct of impulsivity (C. L. Smith & Hantula, 2008). Correlations between delay dis- counting and psychometric measures of impulsivity are typically weak (Reynolds, Ortengren, et al., 2006; Reynolds, Richards, et al., 2006; C. L. Smith & Hantula, 2008).

Where impulsivity is inferred from errors on visual– cognitive tasks, a sex difference in the female direction is found (d 0.26). The use of visuospatial tasks to infer impulsivity also raises problems of validity. These measures were not developed as measures of impulsivity but as tests of, among other things, spatial ability (the Spatial Orientation Dynamic Test–Revised; Quiroga et al., 2007), intelligence (the Porteus Maze, Porteus, 1950; the Tower of London Test, Shallice, 1982), and visual attention (the Trail Making Test; Reitan, 1958). Although the Matching Familiar Figures Test was developed to measure a form of impulsivity, concerns about its construct validity have been raised before (Block et al., 1974). Attributing errors on visuospatial tasks toimpulsivity may be particularly misleading where sex differences are of interest: The sex difference in visuospatial ability is one of the most robust in the literature (Voyer, Voyer, & Bryden, 1995), so a sex difference on these tasks might well be related to this difference in ability rather than impulsivity.

Consistent with Bjorklund and Kipp’s (1996) review, no sex differences were found where impulsivity assessment was based on executive response inhibition tasks. As outlined in previous sections, these included Stroop tasks, the Stop Signal task, and the Go/No-Go task. These tasks are not direct measures of impulsivity but of attention (MacLeod, 1991), inhibitory motor control (Band & van Boxtel, 1999), and passive avoidance learning (Newman, Widom, & Nathan, 1985), respectively. Correlations between these measures and psychometric measures of impulsivity are often weak or absent (Casillas, 2006; Enticott, Ogloff, & Brad- shaw, 2006; Reynolds, Ortengren, et al., 2006; Reynolds, Rich- ards, & de Wit, 2006; Rodr ´guez-Fornells, Lorenzo-Seva, & Andres-Pueyo, 2002; but see Logan, Schachar, & Tannock, 1997).

It has been suggested that performance on the Stop Signal task may be impaired only when trait impulsivity is exceptionally high (Enticott et al., 2006), so that using it to infer impulsivity in normal populations may be problematic.

Moderator analysis.Moderator analyses were conducted for the BART, delay discounting, and executive response inhibition (there were too few studies for moderator analyses related to the IGT or the visuospatial tasks). The results are presented in Table 10. Although small numbers of studies mean that these results must be interpreted with caution, both the analysis by age and the analysis by population suggest that the sex difference in measures of impulsivity based on executive response inhibition is moderated by age. A sex difference in the male direction is present in younger Table 9 Sex Differences in Behavioral Measures of Impulsivity Categoryd95% CI kN QVR (k ) LL ULMen Women Executive response inhibition All studies 0.13 0.04 0.30 19 863 974 84.54 0.94 (19) Computed values only a 0.21 0.06 0.48 10 592 647 83.21 0.94 (19) Visual–cognitive tasks All studies 0.20 0.37 0.04 7 1,558 1,408 172.46 0.92 (8) Computed values only b 0.26 0.43 0.08 6 1,499 1,285 156.43 0.92 (8) Iowa Gambling Task All studies 0.19 0.35 0.03 7 602 725 15.56 — Computed values only c 0.34 0.48 0.20 4 380 420 4.31 — Delay Discounting All studies 0.08 0.19 0.02 21 905 882 40.52 0.95 (17) Computed values only d 0.07 0.22 0.07 15 783 751 39.70 0.95 (17) Balloon Analogue Risk Task All studies 0.30 0.11 0.49 10 265 311 21.12 1.37 (3) Computed values only e 0.36 0.16 0.57 8 220 266 18.93 1.37 (3) Note.Dashes indicate that no variance statistics were reported. Effect sizes are in the male direction if positive and in the female direction if negative.

CI confidence interval;LL lower limit;UL upper limit;Q homogeneity statistic; VR (k ) mean variance ratio (number of sample sizes from which variance ratios could be calculated). aRemoved: Acheson et al. (2007); Brown et al. (2006); de Wit et al. (2002); Feldman (1999); Keilp et al. (2005); Marczinski et al. (2007); Reynolds, Ortengren, et al. (2006); Tinius (2003); Walderhaug (2007). bRemoved: Leshem & Glicksohn (2007). cRemoved: Davis et al. (2007); Goudriaan et al.

(2007); Jollant et al. (2005). dRemoved: Acheson et al. (2007); Allen et al. (1998); de Wit et al. (2002); Kollins (2003). eRemoved: Acheson et al.

(2007); Reynolds (2003); Reynolds et al. (2004); Reynolds, Ortengren, et al. (2006). p .05. p .001. 115 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Table 10 Categorical Analysis of All Measures, Grouped by Domain Measure and categoryd95% CI Q w kQ B LL UL General impulsivity measures Eysenck Impulsiveness Age (years)12.77 10–15 0.07 0.01 0.15 13.88 12 15–18 0.06 0.09 0.20 40.90 11 18–21 0.03 0.02 0.09 45.51 27 21–30 0.09 0.02 0.16 37.52 23 30–40 0.06 0.34 0.23 14.14 5 40 0.21 0.37 0.05 7.79 5 BIS Total Geographical area6.71 United States, Canada, and Central America 0.18 0.09 0.26 68.46 32 United Kingdom, Europe, Australia, and New Zealand 0.05 0.04 0.13 17.01 13 Asia, Africa, and Middle East 0.04 0.03 0.11 0.64 3 KSP Impulsivity Population7.26 University students 0.07 0.09 0.23 0.86 4 Community 0.18 0.27 0.09 0.69 2 Geographical area6.56 United States, Canada, and Central America 0.09 0.09 0.26 0.69 2 United Kingdom, Europe, Australia, and New Zealand 0.17 0.25 0.08 1.59 5 Specific measures of impulsivity BIS Non-Planning Geographical area17.26 United States, Canada, and Central America 0.30 0.20 0.40 11.11 11 United Kingdom, Europe, Australia, and New Zealand 0.02 0.07 0.11 7.80 8 UPPS Perseverance Age (years)13.99 15–18 0.03 0.16 0.11 0.48 2 18–21 0.01 0.18 0.15 15.12 7 UPPS Urgency Population6.85 University students 0.03 0.14 0.07 10.38 9 Schools (up to age 18) 0.26 0.59 0.07 0.18 2 Age (years)15.62 15–18 0.31 0.45 0.17 0.56 2 18–21 0.02 0.07 0.12 1.88 7 21–30 0.14 0.32 0.04 0.41 3 Geographical area6.66 United States, Canada, and Central America 0.04 0.14 0.07 10.42 9 United Kingdom, Europe, Australia, and New Zealand 0.24 0.36 0.12 0.85 4 Sex of first author5.93 Female 0.02 0.14 0.10 9.55 7 Male 0.22 0.33 0.11 1.71 6 Impulse control Age (years)21.98 15–18 0.00 0.74 0.74 26.33 2 18–21 0.40 0.27 0.54 2.43 3 21–30 0.17 0.36 0.03 0.36 2 Geographical area9.18 United States, Canada, and Central America 0.17 0.02 0.35 32.40 8 United Kingdom, Europe, Australia, and New Zealand 0.55 0.98 0.13 4.19 2 Sensation seeking and risk taking Eysenck Venturesomeness Age (years)26.12 10–15 0.46 0.35 0.58 18.84 9 15–18 0.63 0.44 0.81 0.82 3 18–21 0.54 0.43 0.65 27.99 11 116 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. samples (age 10 –15 years,d 0.71; school samples,d 0.62), whereas older samples (21–30 years) show no significant sex difference or a small sex difference in the female direction (com- munity samples,d 0.18). This pattern suggests that, on these tasks, boys may lag behind girls in their ability to inhibit prepotent responses earlier in life, before catching up later on.

Variance ratios.Mean antilog variance ratios can be found in Table 9. No variance ratios were significantly different from 1.

Publication Bias As noted earlier, sex differences were not the object of study in most of the studies retrieved for this meta-analysis, reducing the likelihood of publication bias. Moderator analysis using publica- tion status as a moderator variable found no evidence that effect sizes differed between published and unpublished studies. Further- more, rank correlations between standard error and effect size were not significant (see Table 11). Although in some domains there were insufficient studies to test for publication bias, the tests that could be conducted revealed no evidence for publication bias. Discussion We have organized our discussion in terms of the theoretical distinction made in the introduction between lower order (reward and punishment sensitivity) and higher order (effortful control) theories of impulsivity. We then consider sex differences in vari-ance ratios. We end with a summary and suggestions for future developments in the field. Reward and Punishment Sensitivity in Relation to Sensation Seeking The aggregate measure of reward sensitivity showed no signif- icant sex difference. However, it appears that the various measures within this domain are measuring quite different constructs. On the TCI, items refer specifically to social sensitivity and attachment, and the effect size favoring women probably reflects the greater salience of this domain to women. This pattern may also hold true for the BAS Reward scale, where much emphasis is placed on the strength of emotional responses to positive events. There is evi- dence that women experience emotions more intensely than men and are more willing to articulate them (Brebner, 2003; Vigil, 2009), which may account for women’s higher scores. In contrast, the SPSRQ and GRAPES scales emphasize strong pursuit of reward, particularly in the form of money or status, and here a sex difference favoring men is observed. This sex difference fits well with the predictions outlined in the introduction regarding men’s greater approach motivation in the pursuit of dominance.

Where sex differences in reward sensitivity are of theoretical interest, the choice of reward sensitivity measure is crucial. It is essential to consider what, if any, particular form of reward is most relevant. It must also be made clear whether sensitivity to reward Table 10 (continued) Measure and categoryd95% CI Q w kQ B LL UL 21–30 0.46 0.33 0.58 51.37 60 30–40 0.84 0.70 0.98 1.33 3 40 0.37 0.21 0.53 4.29 4 Reward and punishment sensitivity BAS Reward Age (years)9.75 18–21 0.16 0.29 0.04 6.35 5 21–30 0.54 0.73 0.34 0.02 2 Behavioral measures of impulsivity Balloon Analogue Risk Task Age (years)6.65 10–15 0.43 0.02 0.85 1.15 2 18–21 0.57 0.30 0.85 0.12 3 21–30 0.02 0.30 0.34 0.65 3 Executive response inhibition Population17.37 Community 0.17 0.40 0.06 0.82 4 Schools (up to age 18) 0.62 0.46 0.78 7.58 4 University students 0.05 0.18 0.28 0.35 2 Age (years)30.69 10–15 0.71 0.51 0.92 0.22 2 15–18 0.32 0.36 1.01 5.34 2 21–30 0.19 0.44 0.05 0.47 3 Note.Only significant moderators are shown. Effect sizes are in the male direction if positive and in the female direction if negative. CI confidence interval; LL lower limit;UL upper limit;Q W total within-group variance;Q B variance between contrasted categories; BIS Barratt Impulsiveness Scale; KSP Karolinska Scales of Personality; UPPS Urgency, Premeditation, Perseverance, and Sensation Seeking; BAS Behavioral Activation System. p .05. p .01. p .001. 117 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. refers to the extent to which reward is liked or the extent to which reward is pursued. Our data suggest that this subtle difference in operationalizing sensitivity can lead to sex differences in opposite directions.

Measures of punishment sensitivity were consistently in the female direction. Although the differences between measures were less dramatic than for reward sensitivity, we found again that measures with a stronger emphasis on emotion produced larger sex differences in the female direction. This finding suggests that the extent to which we observe sex differences in punishment sensi- tivity depends on the extent to which measures refer specifically to fear and anxiety, rather than to general dislike or avoidance. As with reward sensitivity, the selection of the appropriate instrument to measure punishment sensitivity will depend on the context of the research.

Explanations of sensation seeking and risk taking have drawn on these lower order theories in terms of affective and neurochemical responses to prospective reward and punishment. It is in the domain of sensation seeking that sex differences were most marked. Sensation seeking is a trait characterized by strong affec- tive motivation— unlike impulsivity, where the presence of affec- tive motivation is ambiguous. We propose that sensation seeking, along with its cousins novelty seeking, risk taking, fun seeking, venturesomeness, and reversed harm avoidance, constitutes a dis- tinctive trait that should not be subsumed under the general con- cept of impulsivity. At a conceptual level, Zuckerman’s (1979) definition of sensation seeking makes no reference to acting with- out deliberation. Zuckerman (1994) himself has noted that para- chute jumpers do not jump from planes on impulse; they plan carefully, checking their equipment, drop site, parachute, and timings. As operationalized in most self-report questionnaires, sensation-seeking items do not make reference to the failure of deliberation, which is the hallmark of impulsive action. Empiri- cally, impulsivity and sensation seeking frequently appear as dis- tinct factors in multivariate analyses. Reviewing 11 factor-analyticstudies of major personality scales, Depue and Collins (1999) found that sensation-seeking, novelty-seeking, and risk-taking scales showed a distinct clustering and were only loosely associ- ated with scales measuring “nonaffective” impulsivity. Several other studies using a range of impulsivity scales have also identi- fied a factor of sensation seeking distinct from other aspects of impulsivity (Flory et al., 2006; Magid & Colder, 2007; Miller, Joseph, & Tudway, 2004; G. T. Smith et al., 2007; Whiteside & Lynam, 2001; Zelenski & Larsen, 1999). That sensation seeking loads on a distinct dimension argues as much for its statistical and conceptual distinctiveness as it does for its status as a facet of impulsivity. In the present analysis, it was noticeable that sex differences were considerably weaker on the ZKPQ ImpSS than on the SSS. When factor-analyzed, ImpSS splits into its two constit- uent factors of impulsivity and sensation seeking (Zuckerman & Kuhlman, 1993). This may account for the dilution of the effect size on this measure, with weaker sex differences in impulsivity counteracting the stronger sex differences in sensation seeking.

Within the domain of sensation seeking and risk taking, we found some encouraging evidence of consistency between psycho- metric and behavioral measures. The BART task was developed as a measure of risk taking (Lejuez et al., 2002), and there is good evidence for its construct validity (Aklin, Lejuez, Zvolensky, Kahler, & Gwadz, 2005; Hunt, Hopko, Bare, Lejuez, & Robinson, 2005). It is not surprising that this task shows a significant sex difference in the male direction. Unlike the behavioral tasks that measured a failure to inhibit a prepotent response, the BART measures the active pursuit of reward. In a factor-analytic study, the BART has been found to be distinct from executive inhibition tasks (Reynolds, Ortengren, et al., 2006). This finding adds to the empirical evidence for a distinction between impulsivity and risk taking.

Evolutionary theories, predicated on differential parental invest- ment, predict higher risk taking by men, and these are supported by the current review. Greater male risk taking is not unique to our Table 11 Evaluation of Evidence for Publication Bias Using Moderator Analysis by Publication Status and Rank Correlation Between Standard Error and Effect Size Domain and measureEffect size by publication status Rank correlation kEvidence for publication bias Published kUnpublished kQ B d95% CId95% CISE p General impulsivity Whole domain 0.07 [0.04, 0.10] 159 0.14 [0.04, 0.25] 21 1.61 0.01 .45 180 None Eysenck Impulsiveness 0.03 [ 0.01, 0.08] 80 0.11 [ 0.04, 0.26] 8 0.92 0.02 .39 88 None BIS Total 0.12 [0.06, 0.19] 44 0.06 [ 0.13, 0.25] 4 0.43 0.10 .16 48 None Impulsivity other measures 0.12 [0.06, 0.18] 38 0.19 [0.04, 0.34] 9 0.67 0.01 .44 47 None Specific measures of impulsivity BIS Non-Planning — — — — — — — 0.06 .36 20 None Sensation seeking and risk taking Whole domain 0.39 [0.34, 0.44] 107 0.37 [0.22, 0.53] 17 0.05 0.05 .20 127 None Eysenck Venturesomeness 0.51 [0.44, 0.57] 44 0.58 [0.03, 1.13] 3 0.07 0.01 .45 49 None SSS Total 0.52 [0.44, 0.60] 16 0.45 [0.31, 0.60] 4 0.64 0.09 .29 20 None Sensation seeking other measures — — — — — — — 0.09 .26 23 None Note.Dashes indicate insufficient studies for analysis by group. The domains of reward sensitivity, punishment sensitivity, and behavioral measures were too small to evaluate. Allpvalues are one-tailed. CI confidence interval;Q B variance between contrasted categories; BIS Barratt Impulsiveness Scale; SSS Sensation Seeking Scale. 118 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. species, and such a conserved and sex-specific evolutionary adap- tation is likely to be instantiated at a relatively low level in terms of neural structure. Emotional and motivational factors are suffi- cient to generate individual differences in appetite for and aversion to risk. Within the evolutionary framework, a distinction can be drawn between Campbell’s (1999) argument that women are more sensitized than men to negative outcomes (punishment sensitivity) and Daly and Wilson’s (1988) argument that men experience a greater positive attraction to risk (reward sensitivity).

Campbell’s (1999) position is supported by our finding that women were consistently higher in measures of punishment sen- sitivity. Women’s risk aversion was also evident in their markedly higher scores on MPQ Harm Avoidance. On this measure, in which respondents choose the less objectionable of two aversive activities, the effect size (d 0.78) is almost twice as big as that found on the SSS Thrill and Adventure scale (d 0.41), which offers an appetitive choice regarding engagement in risky activi- ties. This finding suggests that women may be even more prone to avoid risky activities than men are to seek them out.

In a meta-analysis of sex differences in risk taking, Byrnes, Miller, and Schafer (1999) found greater risk taking by men over a range of paradigms, but these were most marked in studies involving real rather than hypothetical risk. In reference to the distinction between higher level cognitive and lower level moti- vational processes, they noted that “the processes involved in the translation of cognitions to behaviors (e.g., fear responses) may explain gender differences in risk taking more adequately than the cognitive processes involved in the reflective evaluation of op- tions” (Byrnes et al., 1999, p. 378). They proposed that these lower level motivational factors may play as strong a role as cognition in risky decision making. This “risk as feelings” idea was developed by Loewenstein, Weber, Hsee, and Welch (2001), who noted that emotional reactions to risk can and frequently do occur without cognitive intervention, and that sex differences in fear and anxiety underlie women’s more cautious, risk-averse decisions (Lerner & Keltner, 2000). In the areas of health maintenance and extreme sports (Harris, Jenkins, & Glaser, 2006), which present real threats to physical integrity, the sex difference in risk taking is best explained by women’s greater anticipation of negative conse- quences and by their higher ratings of the severity of those nega- tive consequences should they occur.

Although Campbell (1999) originally predicted women’s greater fear specifically in the context of prospective physical injury, many studies have now demonstrated greater fear and anxiety in women across a range of contexts (see Campbell, 2006).

Women exceed men cross-culturally on the Vulnerability (d 0.43) and Anxiety facets (d 0.36) of the NEO Personality Inventory–Revised (Costa et al., 2001). Anxiety is strongly linked to a lower threshold for detecting and attending to threat, and experimental studies demonstrate this threshold to be lower in women than in men (McLean & Anderson, 2009).

Daly and Wilson’s (1988) complementary thesis emphasizes men’s greater attraction to risk. In this view, men engage in more dangerous activities as a result of the inherent attractions of the activities (e.g., scuba diving, parachute jumping). Although it is evident why potentially life-threatening activities might promote fear and avoidance, it is less clear why some individuals should find them inherently attractive. Daly and Wilson argued that men use such activities to advertise their courage as part of intrasexualcompetition, thus gaining greater reproductive success; this mas- culine taste-for-risk therefore represents an evolved module. Con- sistent with this is Zuckerman’s (1994) argument that the physio- logical arousal resulting from such activities signals reward in the brain. Although measures of reward sensitivity do not provide unanimous support for this appetitive view, we note that men’s scores do exceed women’s where questionnaire items focus on competitive dominance striving.

The attraction of risky activities to men, however, need not depend upon heightened male sensitivity to reward but can be explained in terms of their lower punishment sensitivity as follows (Campbell, 2002). Typically an invertedU-shaped function de- scribes the relationship between the arousal (low– high) generated by an activity and its subjective hedonic valence to the actor (pleasant– unpleasant). If men have a higher fear threshold, their function will be right-displaced relative to women’s. Hence a higher degree of arousal will be necessary to generate the same degree of pleasure. Men will show a shift from enjoyment to excitement (and from apprehension to fear) at higher levels of arousal compared with women. Hence a high-speed car ride that is unpleasant (aversive) to women could be exciting (attractive) to men. Effortful Control We consider general measures, specific forms of impulsivity, and behavioral measures as assessing higher order or effortful control, as they presuppose an explicit, conscious decision with regard to action or inaction. The sex difference in general measures of impulsivity, although statistically significant, was small in mag- nitude. The most widely used psychometric measure of general impulsivity, Eysenck’s I 7Impulsiveness questionnaire, showed no significant sex difference. The analysis of specific measures added to the picture of weak, inconsistent sex differences in impulsivity.

Measures of behavioral impulsivity were very inconsistent, with some suggesting greater female impulsivity, some suggesting greater male impulsivity, and some showing no sex difference.

This inconsistency is likely to be related to variation in the con- structs measured by these tasks. Within the domain of higher order processes, it is relevant to highlight the distinction between “hot” effortful control and “cool” executive function control (Ardila, 2008; Happaney, Zelazo, & Stuss, 2004; MacDonald, 2008). Both are higher order processes governing subcortical processes.

Executive function governs cognition in emotionally neutral conditions and has been localized to the dorsolateral prefrontal cortex (Cummings, 1993; Fuster, 1997). Many of the behavioral tasks included in our analysis assess this kind of inhibition, where impulsivity is manifested in an inability to inhibit motor responses, maintain attention, develop and execute a plan, or switch to a new dimensional set. Executive functions of this kind are correlated with general intelligence, where sex differences are likely to be minimal (Jensen, 1998). Our analysis indicates that sex differences are nonsignificant on these cool executive function tasks (Stroop, Go/No-Go, Stop Signal, Continuous Performance Test). The Delay Discounting task also showed no sex difference. Although this task involves monetary incentives and might, therefore, be considered an affective task, we suggest that it relies primarily on the cooler executive form of decision making. In most studies, participants’ choices are entirely hypothetical, because the high sums involved 119 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. (e.g., $1,000) make it impossible to honor their choices. In other studies, participants are told there is a small (e.g., 10%) probability that one of their choices might be honored (e.g., McLeish & Oxoby, 2007), or one trial is randomly selected for payment (e.g., Reynolds, Richards, & de Wit, 2006). Given that participants make as many as 400 sequential choices, it is clear that the task has a strong hypothetical component. Hypothetical decisions draw on cooler cognitive forms of decision making, which are assumed to be based on rationality and expected utility theory (Loewenstein et al., 2001; Madden, Begotka, Raiff, & Kastern, 2003). In their meta-analysis, Byrnes et al. (1999) found a very small tendency for men to make riskier decisions in these hypothetical choice– dilemma tasks (d 0.07).

Although women demonstrated higher impulsivity in visual– cognitive tasks, this result should be treated with caution. Most of these tasks were not originally designed to assess impulsivity. By employing number of errors as the measure of impulsive respond- ing, they conflate men’s established superior visual–spatial abili- ties with lower impulsivity (Voyer et al., 1995). The findings from the IGT should also be treated with caution because, as we have noted, this was not originally designed as an impulsivity measure (Bechara et al., 1994), and the sex difference may reflect women’s greater punishment sensitivity (Goudriaan et al., 2007).

Hot forms of inhibition refer to control over social and affective processes—the effortful control system. It has been localized to the orbitofrontal region of the prefrontal cortex, which has bidirec- tional connections with limbic system structures, notably the amygdala (Davidson, Putnam, & Larson, 2000; Rolls, 2000).

There is suggestive, though not yet conclusive, evidence that women may have an advantage in affective inhibition: Women have greater binding potential for serotonin in several regions including the amygdala and orbitofrontal cortex (Parsey et al., 2002). They also have greater orbitofrontal volume (Goldstein et al., 2001; J. L. Wood, Heitmiller, Andreasen, & Nopoulos, 2008) and greater functional connectivity between the orbitofrontal cor- tex and the amygdala (Meyer-Lindenberg et al., 2006). Following MacDonald’s (2008) and R. F. Baumeister’s (personal communi- cation, February 18, 2010) argument that men’s appetitive im- pulses are less amenable to cortical override than women’s, we anticipated sex differences in effortful control.

The weak sex difference that we found (d 0.08) begs the question of the extent to which psychometric impulsivity measures are accessing hot versus cold inhibitory control. This is not easy to determine. Questions of the kind “I am an impulsive person” do not indicate whether the relevant context is affectively loaded or neutral. Some respondents might interpret this item as referring to affectively hot contexts such as a love affair or an argument, whereas others might think of a cool context such as an ill- considered chess move. Any tendency for men to interpret items in one way and women in another could distort or obscure sex differences. Future studies could usefully examine whether sex differences are systematically moderated by the requirement for hot, as opposed to cool, behavior control. This endeavor would entail clearer exposition of the factors that render a decision affective rather than emotionally neutral. Consider an item such as “I plan tasks carefully.” A negative response to this item might reflect a deficit in the cool executive ability to plan or a social- affective hot preference for spontaneity over predictability.Nonetheless, the management of social interactions appears to be a strong candidate for affective effortful control. In accord with Bjorklund and Kipp’s (1996) proposal, men are more impulsive than women in social problem solving. Whereas this tendency may, as Bjorklund and Kipp suggest, derive from the evolutionary advantages accruing to women who could suppress and conceal emotion toward others, it is also consistent with women’s greater interpersonal interests. Women have been credited with more sensitive social skills and with a stronger interpersonal orientation than men (Cross & Madson, 1997; Hall, 1984; Horgan, Schmid Mast, Hall, & Carter, 2004; Su, Rounds, & Armstrong, 2009). It may be that their superior performance results from a stronger dependence on, and motivation to sustain, social relationships.

This advantage might derive from evolutionary pressures associ- ated with survival and child care (Taylor et al., 2000).

The distinction between executive function and effortful control might reflect more than simply the presence or absence of an affective component. Performance on executive function tasks is often referred to in terms of ability or deficit, implying degrees of competence; impulsive actions are seen as failures of effortful control. As with intelligence, more executive function is better than less. According to this view, sex differences in effortful control will produce male overrepresentation in problem behavior due to men’s greater propensity for failure to act in a controlled manner. It is not clear, however, that effortful control should be viewed in this way. An overly strong effortful control system is associated with internalizing behavior problems (Murray & Kochanska, 2002). Rather than as a competence, effortful control might be best conceptualized as a personality style. In this case, actions that we construe as impulsive represent a preference that might in some circumstances be beneficial (Carver, 2005; Dick- man, 1990; MacDonald, 2008). Stable individual differences will exist in the tendency to make a particular kind of choice, such as spontaneity versus restraint. As with other personality traits (Penke, Denissen, & Miller, 2007), effortful control may be neither an unalloyed good nor an absolute hindrance; it may simply be something that varies between people. According to this trait view of effortful control, a sex difference in effortful control could account for both the overrepresentation of men and boys in exter- nalizing pathologies and the overrepresentation of women and girls in internalizing ones. Understanding whether sex differences in effortful control represent competency failures or personality traits is important in addressing sex-linked social problems includ- ing aggression, substance misuse, and accidental deaths.

Our weak and inconsistent results for effortful control contrast with the very marked sex difference found in children (Else-Quest et al., 2006). Effortful control in children is measured with the Child Behavior Questionnaire (Rothbart, Ahadi, Hershey, & Fisher, 2001) by summing five scales that appear to assess cool executive functions and avoidance of high sensory stimulation. In the former domain, effect sizes were small for the measures of attention focus (d 0.16) and attention shifting (d 0.31).

Effect sizes reflecting tolerance for low levels of sensation were somewhat higher for perceptual sensitivity (detection of slight, low-intensity stimuli;d 0.38), low-intensity pleasure (enjoy- ment of situations involving low-stimulus intensity;d 0.29), and inhibitory control (capacity to suppress approach responses in uncertain situations or when instructed;d 0.41). These latter measures appear to capture aspects of (reversed) sensation hunger.

120 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. It may be that the aggregated effortful control value (d 1.01) disproportionately reflects these sex differences in sensation seek- ing and, if this is the case, is somewhat more consistent with our findings for adults. As noted previously, the Child Behavior Ques- tionnaire assesses impulsiveness separately from effortful control as speed of response initiation (a facet of Surgency/Extraversion).

Here the effect size of 0.18 is only slightly larger than our adult values for several Impulsivity measures. Alternatively, differences in data sources may explain the apparent convergence of the sexes with age. In Else-Quest et al.’s (2006) meta-analysis, the vast majority of the data came from parents’ or teachers’ ratings of child behavior. The larger sex difference they report might reflect gender stereotyping effects associated with third-party reports, a possibility considered by the authors.

To the extent that sex differences in impulsivity do indeed narrow with age, differential neuronal maturation may be a can- didate explanation. Both sexes acquire stronger inhibitory control as they move toward adulthood, which may be tied to the late maturation of prefrontal areas— especially the dorsolateral and ventromedial regions (Hooper, Luciana, Conklin, & Yarger, 2004).

Girls show an earlier maturation peak in frontal lobe areas, but during adolescence, boys show a sharper increase in gray matter reduction and white matter development (Giedd et al., 2006).

There is also evidence that boys and girls may recruit different neuronal circuits to solve the same inhibitory control problem (Christakou et al., 2009). This possibility could be usefully inves- tigated in future work.

Variance Ratios Archer and Mehdikhani (2003) proposed that traits reflecting sexually selected characteristics should show significantly greater variance among men than among women. This proposal stems from the fact that men have more freedom to vary in their sexual strategy in terms of offering high or low levels of paternal invest- ment. Greater male variance, therefore, stems from the retention of both male strategies in the gene pool. Women, as a sex, are more constrained in the levels of maternal investment they must make, which results in lower intrasexual variance. Greater male than female variance has been found on a number of physical (Lehre et al., 2009) and psychological (Archer & Mehdikhani, 2003; Hedges & Nowell, 1995) measures. Operationally, sexual selection is inferred when the sexes vary in central tendency. Sensation seek- ing and punishment sensitivity are therefore candidates for exam- ining Archer and Mehdikhani’s thesis. Variance ratios did not differ significantly from 1 in these or in other impulsivity mea- sures, except on the SSS Disinhibition scale. This null result is surprising given that sex differences in risk taking are thought to arise from differential parental investment (Daly & Wilson, 1988).

Furthermore, differences in central tendency strongly suggest the action of sexual selection. The exclusion criteria of the current analysis might account for this null finding. For reasons outlined in the preceding sections, we excluded clinical and incarcerated sam- ples, which places a constraint on the observed variability. Given the overrepresentation of men and boys in pathological and crim- inal behavior in which risk taking is a factor, it is not unreasonable to suggest that this constraint may affect the male variance more than the female variance, leading to a nonsignificant sex differencehere. Our observation of equal variance is therefore inconclusive, rather than contradictory to Archer and Mehdikhani’s thesis. Summary and Suggestions Our results suggest that sex differences are most evident in low-level motivational responses captured by punishment and re- ward sensitivity, risk taking, and sensation seeking. Where human behavioral sex differences mirror those found in other species, the most likely neural sites are lower level limbic system processes that are phylogenetically conserved. Greater risk taking by men is characteristic of a number of mammalian species (Daly & Wilson, 1983). For example, in common chimpanzees, males are more reckless, impulsive, and active than females (King, Weiss, & Sisco, 2008). The present results suggest that it may be women’s greater sensitivity to and anxiety about the punishing conse- quences of risky action that deters them from the same level of engagement as men.

Sex differences are much smaller for effortful control, which suggests that it has been less subject to sexual selection. The ability to control the expression of emotions is key to sustaining the stable social groups on which both sexes depend (Barkley, 2001; MacDonald, 2008). The enlargement of the human neocortex has been attributed to the need for fast and flexible behavioral adjust- ment to unpredictable changes within the lifetime of the individual (Plotkin, 1997). Such demands have been as great for men as for women, and where selection acts equally on both sexes, sex differences are not expected. The marked overrepresentation of men in aggressive and sexual social pathologies may tell us more about the strength of sexual selection acting on male sexuality and aggression than the natural selection pressures operating on im- pulse restraint.

We end with three lessons that we have learned from undertak- ing this analysis that we hope will be helpful in guiding future research.

Impulsivity is not unitary.In our introduction, we high- lighted the distinctly nonunitary nature of impulsivity as a con- struct. Attempts to integrate various psychometric and behavioral measures into a coherent and replicable set of dimensions have not been entirely successful. This state of affairs may be due to a heavy reliance on factor analysis: The pool of measures entered into the analyses vary between studies, so different results are produced.

Elucidating the dimensionality of impulsivity requires convergent evidence. One promising route might be through imaging studies in which the neural structures and circuits associated with different forms of impulsivity may indicate their distinctiveness (e.g., Dal- ley, Mar, Economidou, & Robbins, 2008; Davidson, Jackson, & Kalin, 2000; Llewellyn, 2008; Meyer-Lindenberg et al., 2006; Smillie, 2008). Until such clarity is achieved, we can only urge caution. Our analysis shows that sex differences depend very much on the inventory or task that is employed. Generalizations from a specific measure to impulsivity more generally must be made tentatively and must acknowledge the multifaceted nature of the construct.

Impulsivity may be both hot and cool.An important dis- tinction within impulsivity is between different forms of higher order control. Executive function is primarily concerned with cognitive aspects of impulsivity manifested in failures of attention maintenance and switching, and the establishment and reorgani- 121 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. zation of dimensional sets. These might rely on different neural structures (dorsolateral prefrontal cortex) than those recruited in effortful control over emotional and affective states (orbitofrontal prefrontal cortex). We found no sex differences in the former and evidence of small differences in the latter. These conclusions must remain tentative until we have a clearer understanding of the extent to which various tasks and measures uniquely assess one system rather than the other. Behavioral tasks vary greatly in which system they engage, and it is often unclear whether a given task is being processed affectively or cognitively. For example, there has been a tendency to assume that the use of monetary incentives is sufficient to render a task affective. It would be helpful to have this contention confirmed by neuroimaging studies, especially in regard to possible sex differences. The corresponding ambiguity in psychometric inventories arises from the use of nonspecific item wording: “I often act without thinking” can be interpreted to apply to cool executive disinhibition (e.g., careless mistakes in solving a mathematical problem) or to an override of affective effortful control (e.g., insulting one’s boss).

Impulsivity is not sensation seeking.There is a clear con- ceptual and empirical distinction between sensation seeking and im- pulsivity. Although there is little unanimity regarding the definition of impulsivity, it has been variously described as acting without delib- eration, failure to inhibit a prepotent response, lack of planning, and failure of perseverance. None of these characteristics applies to sensation-seeking activities. We suggest that sensation seeking should be recognized as a dimension of personality distinct from impulsivity, rather than a trait subsumed by it. Our results provide support for this contention: They clearly indicate that sex differences are small for impulsivity but considerably more marked for sensation seeking.

Using the two constructs interchangeably may produce misleading results with regard to sex differences.

Many impulsive actions are harmless. Hugging someone out of happiness, buying a treat on the spur of the moment, or opting for a new dish at a restaurant are hardly dangerous actions, for the most part. Parachuting, rock climbing, or skiing, although risky, are not generally impulsive. They require planning, training, and a measured consideration of the risk. Yetsome actions may clearly be both impulsive and risky: running across a road, having sex with a stranger, or accepting an offer of drink or drugs, for example (Camp- bell & Muncer, 2009). The assessment of actions that are both risky and impulsive is an area in need of attention. We believe that this form of impulsive risk taking—risky impulsivity—is most likely to under- lie aggressive and criminal behavior. References References marked with an asterisk indicate studies included in the meta-analysis that are discussed in the text. For a complete list, go to http://dx.doi.org/10.1037/a0021591.supp.

*Acheson, A., Richards, J. B., & de Wit, H. (2007). Effects of sleep deprivation on impulsive behaviors in men and women.Physiology & Behavior, 91,579 –587. doi:10.1016/j.physbeh.2007.03.020 *Aklin, W. M., Lejuez, C. W., Zvolensky, M. J., Kahler, C. W., & Gwadz, M. (2005). Evaluation of behavioral measures of risk taking propensity with inner city adolescents.Behaviour Research and Therapy, 43,215– 228. doi:10.1016/j.brat.2003.12.007 *Allen, T. J., Moeller, F. G., Rhoades, H. M., & Cherek, D. R. (1998).

Impulsivity and history of drug dependence.Drug and Alcohol Depen- dence, 50,137–145. doi:10.1016/S0376-8716(98)00023-4Aluja, A., & Torrubia, R. (2004). Hostility–aggressiveness, sensation seek- ing and sex hormones in men: Re-exploring their relationship.Neuro- psychobiology, 50,102–107. doi:10.1159/000077947 American Psychiatric Association. (2000).Diagnostic and statistical man- ual of mental disorders(4th ed., text rev.). Washington, DC: Author.

doi:10.1176/appi.books.9780890423349 *Anestis, M. D., Selby, E. A., & Joiner, T. E. (2007). The role of urgency in maladaptive behaviors.Behaviour Research and Therapy, 45,3018 – 3029. doi:10.1016/j.brat.2007.08.012 Archer, J. (2004). Sex differences in aggression in real-world settings: A meta-analytic review.Review of General Psychology, 8,291–322. doi:

10.1037/1089-2680.8.4.291 Archer, J. (2006). Testosterone and human aggression: An evaluation of the challenge hypothesis.Neuroscience and Biobehavioral Reviews, 30, 319 –335. doi:10.1016/j.neubiorev.2004.12.007 Archer, J. (2009). Does sexual selection explain human sex differences in aggression?Behavioral and Brain Sciences, 32,266 –311. doi:10.1017/ S0140525X09990951 Archer, J., & Mehdikhani, M. (2003). Variability among males in sexually selected attributes.Review of General Psychology, 7,219 –236. doi:

10.1037/1089-2680.7.3.219 Ardila, A. (2008). On the evolutionary origins of executive functions.

Brain and Cognition, 68,92–99. doi:10.1016/j.bandc.2008.03.003 Arneklev, B. J., Grasmick, H. G., Tittle, C. R., & Bursik, R. J. (1993). Low self-control and imprudent behavior.Journal of Quantitative Criminol- ogy, 9,225–247. doi:10.1007/BF01064461 Arnett, J. (1994). Sensation seeking: A new conceptualization and a new scale.Personality and Individual Differences, 16,289 –296. doi:

10.1016/0191-8869(94)90165-1 *A´ vila, C., & Parcet, M. A. (2000). The role of Gray’s impulsivity in anxiety-mediated differences in resistance to extinction.European Jour- nal of Personality, 14,185–198. doi:10.1002/1099-0984(200005/06) 14:3 185::AID-PER370 3.0.CO;2-U Ball, S. A., & Zuckerman, M. (1990). Sensation seeking, Eysenck’s per- sonality dimensions and reinforcement sensitivity in concept formation.

Personality and Individual Differences, 11,343–353. doi:10.1016/0191- 8869(90)90216-E Band, G. P. H., & van Boxtel, G. J. M. (1999). Inhibitory motor control in stop paradigms: Review and reinterpretation of neural mechanisms.Acta Psychologica, 101,179 –211. doi:10.1016/S0001-6918(99)00005-0 Bar-Haim, Y., Lamy, D., Pergamin, L., Bakermans-Kranenburg, M. J., & van IJzendoorn, M. H. (2007). Threat-related attentional bias in anxious and nonanxious individuals: A meta-analytic study.Psychological Bul- letin, 133,1–24. doi:10.1037/0033-2909.133.1.1 Barkley, R. A. (2001). The executive functions and self-regulation: An evolutionary neuropsychological perspective.Neuropsychology Review, 11,1–29. doi:10.1023/A:1009085417776 Barlow, D. H. (2002).Anxiety and its disorders: The nature and treatment of anxiety and panic(2nd ed.). New York, NY: Guilford Press. doi:

10.1016/S1077-7229(03)80027-5 Barratt, E. S. (1985). Impulsiveness subtraits: Arousal and information processing. In J. T. Spence & C. E. Izard (Eds.),Motivation, emotion and personality(pp. 137–146). Amsterdam, the Netherlands: Elsevier.

Baumeister, R. F., Vohs, K. D., & Tice, D. M. (2007). The strength model of self-control.Current Directions in Psychological Science, 16,351– 355. doi:10.1111/j.1467-8721.2007.00534.x Beattie, G. (2008).Sex differences in driving and insurance risk: Under- standing the neurobiological and evolutionary foundations of the differ- ences.Manchester, England: University of Manchester.

Bechara, A., Damasio, A. R., Damasio, H., & Anderson, S. W. (1994).

Insensitivity to future consequences following damage to human pre- frontal cortex.Cognition, 50,7–15. doi:10.1016/0010-0277(94)90018-3 Bechara, A., Damasio, H., Tranel, D., & Damasio, A. R. (1997). Deciding 122 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. advantageously before knowing the advantageous strategy.Science, 275, 1293–1295. doi:10.1126/science.275.5304.1293 Begg, C. B., & Mazumdar, M. (1994). Operating characteristics of a rank correlation test for publication bias.Biometrics, 50,1088 –1101. doi:

10.2307/2533446 *Bembenutty, H., & Karabenick, S. A. (1998). Academic delay of grati- fication.Learning and Individual Differences, 10,329 –346. doi:

10.1016/S1041-6080(99)80126-5 Bettencourt, B. A., & Miller, N. (1996). Gender differences in aggression as a function of provocation: A meta-analysis.Psychological Bulletin, 119,422– 447. doi:10.1037/0033-2909.119.3.422 Bijttebier, P., Beck, I., Claes, L., & Vandereycken, W. (2009). Gray’s reinforcement sensitivity theory as a framework for research on personality–psychopathology associations.Clinical Psychology Review, 29,421– 430. doi:10.1016/j.cpr.2009.04.002 Bjorklund, D. F., & Kipp, K. (1996). Parental investment theory and gender differences in the evolution of inhibition mechanisms.Psycho- logical Bulletin, 120,163–188. doi:10.1037/0033-2909.120.2.163 Blackwell, B. S., & Piquero, A. R. (2005). On the relationships between gender, power control, self-control and crime.Journal of Criminal Justice, 33,1–17. doi:10.1016/j.jcrimjus.2004.10.001 Block, J., Block, J. H., & Harrington, D. M. (1974). Some misgivings about the Matching Familiar Figures Test as a measure of reflection– impulsivity.Developmental Psychology, 10,611– 632. doi.org/10.1037/ h0037047 Borenstein, M., Hedges, L., Higgins, J., & Rothstein, H. (2005).Compre- hensive meta-analysis Version 2[Computer software]. Englewood, NJ:

Biostat.

Borenstein, M., Hedges, L. V., Higgins, J. P. T., & Rothstein, H. R. (2009).

Introduction to meta-analysis.Chichester, England: Wiley. doi:10.1002/ 9780470743386 Brebner, J. (2003). Gender and emotions.Personality and Individual Differences, 34,387–394. doi:10.1016/S0191-8869(02)00059-4 *Brown, S. M., Manuck, S. B., Flory, J. D., & Hariri, A. R. (2006). Neural basis of individual differences in impulsivity: Contributions of corti- colimbic circuits for behavioral arousal and control.Emotion, 6,239 – 245. doi:10.1037/1528-3542.6.2.239 Burton, V. S., Jr., Cullen, F. T., Evans, T. D., Alarid, L. F., & Dunaway, R. G.

(1998). Gender, self-control, and crime.Journal of Research in Crime and Delinquency, 35,123–147. doi:10.1177/0022427898035002001 Byrnes, J. P., Miller, D. C., & Schafer, W. D. (1999). Gender differences in risk taking: A meta-analysis.Psychological Bulletin, 125,367–383.

doi:10.1037/0033-2909.125.3.367 Cale, E. M., & Lilienfeld, S. O. (2002). Sex differences in psychopathy and antisocial personality disorder: A review and integration.Clinical Psy- chology Review, 22,1179 –1207. doi:10.1016/S0272-7358(01)00125-8 Campbell, A. (1999). Staying alive: Evolution, culture and women’s ag- gression.Behavioral and Brain Sciences, 22,203–252. doi:10.1017/ S0140525X99001818 Campbell, A. (2002).A mind of her own: The evolutionary psychology of women.Oxford, England: Oxford University Press. doi:10.1093/acprof:

oso/9780198504986.001.0001 Campbell, A. (2006). Sex differences in direct aggression: What are the psychological mediators?Aggression and Violent Behavior, 11,237– 264. doi:10.1016/j.avb.2005.09.002 Campbell, A., & Muncer, S. (2009). Can “risky” impulsivity explain sex differences in aggression?Personality and Individual Differences, 47, 402– 406. doi:10.1016/j.paid.2009.04.006 Carver, C. S. (2005). Impulse and constraint: Perspectives from personality psychology, convergence with theory in other areas, and potential for integration.Personality and Social Psychology Review, 9,312–333.

doi:10.1207/s15327957pspr0904_2 Carver, C. S., & White, T. L. (1994). Behavioral inhibition, behavioral activation, and affective responses to impending reward and punishment:The BIS/BAS Scales.Journal of Personality and Social Psychology, 67, 319 –333. doi:10.1037/0022-3514.67.2.319 *Caseras, X., A´ vila, C., & Torrubia, R. (2003). The measurement of individual differences in Behavioural Inhibition and Behavioural Acti- vation Systems: A comparison of personality scales.Personality and Individual Differences, 34,999 –1013. doi:10.1016/S0191-8869 (02)00084-3 Casey, B. J., Getz, S., & Galvan, A. (2008). The adolescent brain.Devel- opmental Review, 28,62–77. doi:10.1016/j.dr.2007.08.003 *Casillas, A. (2006). Personality and neuropsychological correlates of impulsivity.Dissertation Abstracts International: Section B. Sciences and Engineering, 66(8), 4476.

Center for Well-Being. (n.d.).TCI: A comprehensive assessment of per- sonality.St. Louis, MO: Washington University School of Medicine.

Retrieved from http://psychobiology.wustl.edu/joomla Christakou, A., Halari, R., Smith, A. B., Ifkovits, E., Brammer, M., & Rubia, K. (2009). Sex-dependent age modulation of frontostriatal and temporo-parietal activation during cognitive control.NeuroImage, 48, 223–236. doi:10.1016/j.neuroimage.2009.06.070 *Chung, T., & Martin, C. S. (2002). Concurrent and discriminant validity ofDSM–IVsymptoms of impaired control over alcohol consumption in adolescents.Alcoholism: Clinical and Experimental Research, 26,485– 492. doi:10.1111/j.1530-0277.2002.tb02565.x *Clark, L., Roiser, J. P., Cools, R., Rubinsztein, D. C., Sahakian, B. J., & Robbins, T. W. (2005). Stop signal response inhibition is not modulated by tryptophan depletion or the serotonin transporter polymorphism in healthy volunteers: Implications for the 5-HT theory of impulsivity.

Psychopharmacology, 182,570 –578. doi:10.1007/s00213-005-0104-6 *Clarke, D. (2004). Impulsiveness, locus of control, motivation and prob- lem gambling.Journal of Gambling Studies, 20,319 –345. doi:10.1007/ s10899-004-4578-7 Cloninger, C. R. (1986). A unified biosocial theory of personality and its role in the development of anxiety states.Psychiatric Developments, 4, 167–226.

Cloninger, C. R. (1987). A systematic method for clinical description and classification of personality variants. A proposal.Archives of General Psychiatry, 44,573–588.

Coccaro, E. F., Beresford, B., Minar, P., Kaskow, J., & Geracioti, T.

(2007). CSF testosterone: Relationship to aggression, impulsivity, and venturesomeness in adult males with personality disorder.Journal of Psychiatric Research, 41,488 – 492. doi:10.1016/j.jpsychires .2006.04.009 Colom, R., Contreras, M. J., Shih, P. C., & Santacreu, J. (2003). The assessment of spatial ability with a single computerized test.European Journal of Psychological Assessment, 19,92–100. doi:10.1027//1015- 5759.19.2.92 Conners, C. K. (2000).Conner’s Continuous Performance Test (CPT II).

North Tonawanda, NY: Multi-Health Systems.

*Copping, L. T. (2007).Social class and social representation: Is impul- sivity the mediator?(Unpublished master’s thesis). Department of Psy- chology, Durham University, Stockton-on-Tees, England.

*Corr, P. J., Pickering, A. D., & Gray, J. A. (1995). Sociability/impulsivity and caffeine-induced arousal: Critical flicker/fusion frequency and pro- cedural learning.Personality and Individual Differences, 18,713–730.

doi:10.1016/0191-8869(95)00001-M Costa, P. T., Jr., & McCrae, R. R. (1992).Revised NEO Personality Inventory (NEO-PI–R) and NEO Five Factor Inventory (NEO-FFI) professional manual.Odessa, FL: Psychological Assessment Resources.

Costa, P. T., Jr., Terracciano, A., & McCrae, R. R. (2001). Gender differences in personality traits across cultures: Robust and surprising findings.Journal of Personality and Social Psychology, 81,322–331.

doi:10.1037/0022-3514.81.2.322 Crean, J. P., de Wit, H., & Richards, J. B. (2000). Reward discounting as a measure of impulsive behavior in a psychiatric outpatient population. 123 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Experimental and Clinical Psychopharmacology, 8,155–162. doi:

10.1037/1064-1297.8.2.155 Cross, S. E., & Madson, L. (1997). Models of the self: Self-construals and gender.Psychological Bulletin, 122,5–37. doi:10.1037/0033- 2909.122.1.5 Cummings, J. L. (1993). Frontal-subcortical circuits and human behaviour.

Archives of Neurology, 50,873– 880.

*Curran, M. F. (2006). Risk taking as a contributing factor to driving while under the influence of alcohol.Dissertation Abstracts International:

Section B. Sciences and Engineering, 67(3), 1741.

Daitzman, R. J., & Zuckerman, M. (1980). Disinhibitory sensation seeking, personality and gonadal hormones.Personality and Individual Differ- ences, 1,103–110. doi:10.1016/0191-8869(80)90027-6 Dalley, J. W., Mar, A. C., Economidou, D., & Robbins, T. W. (2008).

Neurobehavioral mechanisms of impulsivity: Fronto-striatal systems and functional neurochemistry.Pharmacology, Biochemistry and Behavior, 90,250 –260. doi:10.1016/j.pbb.2007.12.021 Daly, M., & Wilson, M. (1983).Sex, evolution and behavior: Adaptations for reproduction.Boston, MA: Willard Grant Press.

Daly, M., & Wilson, M. (1988).Homicide.New York, NY: Aldine de Gruyter.

Davidson, R. J., Jackson, D. C., & Kalin, N. H. (2000). Emotion, plasticity, context, and regulation: Perspectives from affective neuroscience.Psy- chological Bulletin, 126,890 –909. doi:10.1037/0033-2909.126.6.890 Davidson, R. J., Putnam, K. M., & Larson, C. L. (2000). Dysfunction in the neural circuitry of emotion regulation—A possible prelude to violence.

Science, 289,591–594. doi:10.1126/science.289.5479.591 *Davis, C., Patte, K., Tweed, S., & Curtis, C. (2007). Personality traits associated with decision-making deficits.Personality and Individual Differences, 42,279 –290. doi:10.1016/j.paid.2006.07.006 Dawe, S., Gullo, M. J., & Loxton, N. J. (2004). Reward drive and rash impulsiveness as dimensions of impulsivity: Implications for substance misuse.Addictive Behaviors, 29,1389 –1405. doi:10.1016/j.addbeh .2004.06.004 *Deffenbacher, J. L., Filetti, L. B., Richards, T. L., Lynch, R. S., & Oetting, E. R. (2003). Characteristics of two groups of angry drivers.

Journal of Counseling Psychology, 50,123–132. doi:10.1037/0022- 0167.50.2.123 Degenhardt, L., Chiu, W.-T., Sampson, N., Kessler, R. C., Anthony, J. C., Angermeyer, M., . . . Wells, J. E. (2008). Toward a global view of alcohol, tobacco, cannabis, and cocaine use: Findings from the WHO World Mental Health Surveys.PLoS Medicine, 5,e141. doi:10.1371/ journal.pmed.0050141 Depue, R. A., & Collins, P. F. (1999). Neurobiology of the structure of personality: Dopamine, facilitation of incentive motivation, and extra- version.Behavioral and Brain Sciences, 22,491–569. doi:10.1017/ S0140525X99002046 Derryberry, D., & Rothbart, M. K. (1997). Reactive and effortful processes in the organization of temperament.Development and Psychopathology, 9,633– 652. doi:10.1017/S0954579497001375 Deschenes, E. P., & Esbensen, F. A. (1999). Violence and gangs: Gender differences in perceptions and behavior.Journal of Quantitative Crim- inology, 15,63–96. doi:10.1023/A:1007552105190 *de Wit, H., Engasser, J. L., & Richards, J. B. (2002). Acute administration ofd-amphetamine decreases impulsivity in healthy volunteers.Neuro- psychopharmacology, 27,813– 825. doi:10.1016/S0893-133X(02) 00343-3 Dickman, S. J. (1990). Functional and dysfunctional impulsivity: Person- ality and cognitive correlates.Journal of Personality and Social Psy- chology, 58,95–102. doi:10.1037/0022-3514.58.1.95 Dickman, S. J., & Meyer, D. E. (1988). Impulsivity and speed–accuracy tradeoffs in information processing.Journal of Personality and Social Psychology, 54,274 –290. doi:10.1037/0022-3514.54.2.274 *Dinn, W. M., Harris, C. L., Aycicegi, A., Greene, P., & Andover, M. S.(2002). Positive and negative schizotypy in a student sample: Neuro- cognitive and clinical correlates.Schizophrenia Research, 56,171–185.

doi:10.1016/S0920-9964(01)00230-4 *Doran, N., McChargue, D., & Cohen, L. (2007). Impulsivity and the reinforcing value of cigarette smoking.Addictive Behaviors, 32,90 –98.

doi:10.1016/j.addbeh.2006.03.023 Dougherty, D. M., Mathias, C. W., Marsh-Richard, D. M., Furr, R. M., Nouvion, S. O., & Dawes, M. A. (2009). Distinctions in behavioral impul- sivity: Implications for substance abuse research.Addictive Disorders and Their Treatment, 8,61–73. doi:10.1097/ADT.0b013e318172e488 D’Zurilla, T., Nezu, A., & Maydeu-Olivares, A. (1996).Manual for the Social Problem-Solving Inventory–Revised.North Tonawanda, NY:

Multi-Health Systems.

Eagly, A. H., & Steffen, V. J. (1986). Gender and aggressive behavior: A meta-analytic review of the social psychological literature.Psychologi- cal Bulletin, 100,309 –330. doi:10.1037/0033-2909.100.3.309 Else-Quest, N. M., Hyde, J. S., Goldsmith, H. H., & Van Hulle, C. A.

(2006). Gender differences in temperament: A meta-analysis.Psycho- logical Bulletin, 132,33–72. doi:10.1037/0033-2909.132.1.33 *Enticott, P. G., Ogloff, J. R. P., & Bradshaw, J. L. (2006). Associations between laboratory measures of executive inhibitory control and self- reported impulsivity.Personality and Individual Differences, 41,285– 294. doi:10.1016/j.paid.2006.01.011 Evenden, J. L. (1999). Varieties of impulsivity.Psychopharmacology, 146, 348 –361. doi:10.1007/PL00005481 Eysenck, H. J., & Eysenck, M. W. (1985).Personality and individual differences: A natural science approach.New York, NY: Plenum Press.

Eysenck, H. J., & Eysenck, S. B. G. (1968).Manual for the Eysenck Personality Inventory.San Diego, CA: Educational and Industrial Test- ing Service.

Eysenck, H. J., & Gudjonsson, G. H. (1989).The causes and cures of criminality.New York, NY: Plenum Press.

Eysenck, S. B. G. (1993). The I 7: Development of a measure of impulsivity and its relationship to the superfactors of personality. In W. G. McCown, J. L. Johnson, & M. B. Shure (Eds.),The impulsive client: Theory, research, and treatment(pp. 141–149). Washington, DC: American Psychological Association. doi:10.1037/10500-009 Eysenck, S. B. G., & Eysenck, H. J. (1978). Impulsiveness and venture- someness: Their position in a dimensional system of personality descrip- tion.Psychological Reports, 43,1247–1255.

*Eysenck, S. B. G., Pearson, P. R., Easting, G., & Allsopp, J. F. (1985).

Age norms for impulsiveness, venturesomeness and empathy in adults.

Personality and Individual Differences, 6,613– 619. doi:10.1016/0191- 8869(85)90011-X Feingold, A. (1994). Gender differences in personality: A meta-analysis.

Psychological Bulletin, 116,429 – 456. doi:10.1037/0033-2909 .116.3.429 *Feldman, D. J. (1999). Haste and disinhibition: An analysis of impulsive cognitive style manifest in adult performance on neuropsychological measures.Dissertation Abstracts International: Section B. Sciences and Engineering, 59(11), 6063.

Fischer, A. H., & Manstead, A. S. R. (2000). The relation between gender and emotion in different cultures. In A. H. Fischer (Ed.),Gender and emotion:

Social psychological perspectives(pp. 71–94). Cambridge, England: Cam- bridge University Press. doi:10.1017/CBO9780511628191 *Flory, J. D., Harvey, P. D., Mitropoulou, V., New, A. S., Silverman, J. M., Siever, L. J., & Manuck, S. B. (2006). Dispositional impulsivity in normal and abnormal samples.Journal of Psychiatric Research, 40, 438 – 447. doi:10.1016/j.jpsychires.2006.01.008 Fowles, D. C. (1987). Application of a behavioural theory of motivation to the concepts of anxiety and impulsivity.Journal of Research in Person- ality, 21,417– 435. doi:10.1016/0092-6566(87)90030-4 Fowles, D. C. (1988). Psychophysiology and psychopathology: A motiva- 124 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. tional approach.Psychophysiology, 25,373–391. doi:10.1111/j.1469- 8986.1988.tb01873.x *Fox, H. C., Axelrod, S. R., Paliwal, P., Sleeper, J., & Sinha, R. (2007).

Difficulties in emotion regulation and impulse control during cocaine abstinence.Drug and Alcohol Dependence, 89,298 –301. doi:10.1016/ j.drugalcdep.2006.12.026 Frank, E. (Ed.). (2000).Gender and its effects on psychopathology.Ar- lington, VA: American Psychiatric Press.

Franken, I. H. A., & Muris, P. (2006). Gray’s impulsivity dimension: A distinction between reward sensitivity versus rash impulsiveness.Per- sonality and Individual Differences, 40,1337–1347. doi:10.1016/ j.paid.2005.11.016 Fuster, J. M. (1997).The prefrontal cortex: Anatomy, physiology and neuropsychology(3rd ed.). Philadelphia, PA: Lippincott-Raven.

Gerbing, D. W., Ahadi, S. A., & Patton, J. H. (1987). Toward a concep- tualization of impulsivity: Components across the behavioral and self- report domains.Multivariate Behavioral Research, 22,357–379. doi:

10.1207/s15327906mbr2203_6 Gershon, J., & Gershon, J. (2002). A meta-analytic review of gender differences in ADHD.Journal of Attention Disorders, 5,143–154.

doi:10.1177/108705470200500302 Giedd, J. N., Clasen, L. S., Lenroot, R., Greenstein, D., Wallace, G. L., Ordaz, S., . . . Chrousos, G. P. (2006). Puberty-related influences on brain development.Molecular and Cellular Endocrinology, 254 –255, 154 –162. doi:10.1016/j.mce.2006.04.016 Goldstein, J. M., Seidman, L. J., Horton, N. J., Makris, N., Kennedy, D. N., Caviness, V. S., Jr., . . . Tsuang, M. T. (2001). Normal sexual dimor- phism of the adult human brain assessed by in vivo magnetic resonance imaging.Cerebral Cortex, 11,490 – 497. doi:10.1093/cercor/11.6.490 Gomez, R., & Gomez, A. (2005). Convergent, discriminant and concurrent validities of measures of the behavioural approach and behavioural inhibition systems: Confirmatory factor analytic approach.Personality and Individual Differences, 38,87–102. doi:10.1016/j.paid.2004.03.011 Gottfredson, M., & Hirschi, T. (1990).A general theory of crime.Stanford, CA: Stanford University Press.

*Goudriaan, A. E., Grekin, E. R., & Sher, K. J. (2007). Decision making and binge drinking: A longitudinal study.Alcoholism: Clinical and Experimental Research, 31,928 –938. doi:10.1111/j.1530-0277 .2007.00378.x Grasmick, H. G., Tittle, C. R., Bursik, R. J., Jr., & Arneklev, B. J. (1993).

Testing the core empirical implications of Gottfredson and Hirschi’s general theory of crime.Journal of Research in Crime and Delinquency, 30,5–29. doi:10.1177/0022427893030001002 Gray, J. A. (1970). The psychophysiological basis of introversion– extraversion.Behaviour Research and Therapy, 8,249 –266. doi:

10.1016/0005-7967(70)90069-0 Gray, J. A. (1982).The neuropsychology of anxiety: An enquiry into the functions of the septo-hippocampal system.Oxford, England: Oxford University Press.

Gray, J. A., & McNaughton, N. (2000).The neuropsychology of anxiety:

An enquiry into the functions of the septo-hippocampal system(2nd ed.).

Oxford, England: Oxford University Press.

Hall, J. A. (1984).Nonverbal sex differences: Communication accuracy and expressive style.Baltimore, MD: Johns Hopkins University Press.

Happaney, K., Zelazo, P. D., & Stuss, D. T. (2004). Development of orbitofrontal function: Current themes and future directions.Brain and Cognition, 55,1–10. doi:10.1016/j.bandc.2004.01.001 Hardy, R. J., & Thompson, S. G. (1998). Detecting and describing heter- ogeneity in meta-analysis.Statistics in Medicine, 17,841– 856.

doi:10.1002/(SICI)1097-0258(19980430)17:8 841::AID-SIM781 3.0.CO;2-D Harris, C. R., Jenkins, M., & Glaser, D. (2006). Gender differences in risk assessment: Why do women take fewer risks than men?Judgment and Decision Making Journal, 1,48 – 63.Hedges, L. V., & Nowell, A. (1995). Sex differences in mental test scores, variability, and numbers of high-scoring individuals.Science, 269,41– 45. doi:10.1126/science.7604277 Hedges, L. V., & Olkin, I. (1985).Statistical methods for meta-analysis.

London, England: Academic Press.

Hedges, L. V., & Pigott, T. D. (2004). The power of statistical tests for moderators in meta-analysis.Psychological Methods, 9,426 – 445. doi:

10.1037/1082-989X.9.4.426 Helmers, K. F., Young, S. N., & Pihl, R. O. (1995). Assessment of measures of impulsivity in healthy male volunteers.Personality and Individual Differences, 19,927–935. doi:10.1016/S0191-8869 (95)00107-7 Heym, N., Ferguson, E., & Lawrence, C. (2008). An evaluation of the relationship between Gray’s revised RST and Eysenck’s PEN: Distin- guishing BIS and FFFS in Carver and White’s BIS/BAS scales.Per- sonality and Individual Differences, 45,709 –715. doi:10.1016/ j.paid.2008.07.013 Higgins, J. P. T. (2008). Commentary: Heterogeneity in meta-analysis should be expected and appropriately quantified.International Journal of Epidemiology, 37,1158 –1160. doi:1158-1160.10.1093/ije/dyn204 Higgins, J. P. T., & Thompson, S. G. (2002). Quantifying heterogeneity in a meta-analysis.Statistics in Medicine, 21,1539 –1558. doi:10.1002/ sim.1186 Hooper, C. J., Luciana, M., Conklin, H. M., & Yarger, R. S. (2004).

Adolescents’ performance on the Iowa Gambling Task: Implications for the development of decision making and ventromedial prefrontal cortex.

Developmental Psychology, 40,1148 –1158. doi:10.1037/0012- 1649.40.6.1148 Horgan, T. G., Schmid Mast, M., Hall, J. A., & Carter, J. D. (2004).

Gender differences in memory for the appearance of others.Person- ality and Social Psychology Bulletin, 30,185–196. doi:10.1177/ 0146167203259928 Hsu, C., Soong, W., Stigler, J. W., Hong, C., & Liang, C. (1981). The temperamental characteristics of Chinese babies.Child Development, 52,1337–1340. doi:10.2307/1129528 *Hulsey, C. D. (2001). Predictors of problem gambling among college students.Dissertation Abstracts International: Section B. Sciences and Engineering, 61(7), 3847.

*Hunt, M. K., Hopko, D. R., Bare, R., Lejuez, C. W., & Robinson, E. V.

(2005). Construct validity of the Balloon Analog Risk Task (BART):

Associations with psychopathy and impulsivity.Assessment, 12,416 – 428. doi:10.1177/1073191105278740 Hyde, J. S. (1986). Gender differences in aggression. In J. S. Hyde & M. C.

Linn (Eds.),The psychology of gender: Advances through meta-analysis (pp. 51– 66). Baltimore, MD: Johns Hopkins University Press.

*Jack, S. J., & Ronan, K. R. (1998). Sensation seeking among high- and low-risk sports participants.Personality and Individual Differences, 25, 1063–1083. doi:10.1016/S0191-8869(98)00081-6 Jackson, D. N. (1994).Jackson Personality Inventory–Revised manual.

Port Huron, MI: Research Psychologists Press.

Jensen, A. R. (1998).Thegfactor: The science of mental ability.Westport, CT: Praeger.

*Jollant, F., Bellivier, F., Leboyer, M., Astruc, B., Torres, S., Verdier, R.,...Courtet, P. (2005). Impaired decision making in suicide attempt- ers.American Journal of Psychiatry, 162,304 –310. doi:10.1176/ appi.ajp.162.2.304 Kagan, J., Rosman, B. L., Kay, D., Albert, J., & Phillips, W. (1964).

Information processing in the child: Significance of analytic and reflec- tive attitudes.Psychological Monographs: General and Applied, 78(1, Whole No. 578).

Keane, C., Maxim, P. S., & Teevan, J. J. (1993). Drinking and driving, self-control, and gender: Testing a general theory of crime.Journal of Research in Crime and Delinquency, 30,30 – 46. doi:10.1177/ 0022427893030001003 125 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. *Keilp, J. G., Sackeim, H. A., & Mann, J. J. (2005). Correlates of trait impulsiveness in performance measures and neuropsychological tests.

Psychiatry Research, 135,191–201. doi:10.1016/j.psychres.2005.03.006 Kessler, R. C., Coccaro, E. F., Fava, M., Jaeger, S., Jin, R., & Walters, E.

(2006). The prevalence and correlates ofDSM–IVintermittent explosive disorder in the National Comorbidity Survey Replication.Archives of General Psychiatry, 63,669 – 678. doi:10.1001/archpsyc.63.6.669 *Ketzenberger, K. E., & Forrest, L. (2000). Impulsiveness and compul- siveness in alcoholics and nonalcoholics.Addictive Behaviors, 25,791– 795. doi:10.1016/S0306-4603(00)00062-9 Kindlon, D. J., Mezzacappa, E., & Earls, F. (1995). Psychometric proper- ties of impulsivity measures: Temporal stability, validity and factor structure.Journal of Child Psychology and Psychiatry, 36,645– 661.

doi:10.1111/j.1469-7610.1995.tb01316.x King, J. E., Weiss, A., & Sisco, M. M. (2008). Aping humans: Age and sex effects in chimpanzee (Pan troglodytes) and human (Homo sapiens) personality.Journal of Comparative Psychology, 122,418 – 427. doi:

10.1037/a0013125 Kirby, K. N., Petry, N. M., & Bickel, W. K. (1999). Heroin addicts have higher discount rates for delayed rewards than non-drug-using controls.

Journal of Experimental Psychology: General, 128,78 – 87. doi:

10.1037/0096-3445.128.1.78 Knight, G. P., Fabes, R. A., & Higgins, D. A. (1996). Concerns about drawing causal inferences from meta-analyses: An example in the study of gender differences in aggression.Psychological Bulletin, 119,410 – 421. doi:10.1037/0033-2909.119.3.410 Knight, G. P., Guthrie, I. K., Page, M. C., & Fabes, R. A. (2002).

Emotional arousal and gender differences in aggression: A meta- analysis.Aggressive Behavior, 28,366 –393. doi:10.1002/ab.80011 Kochanska, G., & Knaack, A. (2003). Effortful control as a personality characteristic of young children: Antecedents, correlates, and conse- quences.Journal of Personality, 71,1087–1112. doi:10.1111/1467- 6494.7106008 *Kollins, S. H. (2003). Delay discounting is associated with substance use in college students.Addictive Behaviors, 28,1167–1173. doi:10.1016/ S0306-4603(02)00220-4 Kruger, D. J., & Nesse, R. M. (2006). An evolutionary life-history frame- work for understanding sex differences in human mortality rates.Human Nature, 17,74 –97. doi:10.1007/s12110-006-1021-z LaGrange, T. C., & Silverman, R. A. (1999). Low self-control and oppor- tunity: Testing the general theory of crime as an explanation for gender differences in delinquency.Criminology, 37,41–72. doi:10.1111/j.1745- 9125.1999.tb00479.x Lane, S. D., Cherek, D. R., Rhodes, H. M., Pietras, C. J., & Tcheremissine, O. V. (2003). Relationships among laboratory and psychometric mea- sures of impulsivity: Implications in substance abuse and dependence.

Addictive Disorders and Their Treatment, 2,33– 40. doi:10.1097/ 00132576-200302020-00001 Larsen, C. S. (2003). Equality for the sexes in human evolution? Early hominid sexual dimorphism and implications for mating systems and social behavior.Proceedings of the National Academy of Sciences, USA, 100,9103–9104. doi:10.1073/pnas.1633678100 Lehre, A.-C., Lehre, K. P., Laake, P., & Danbolt, N. C. (2009). Greater intrasex phenotype variability in males than in females is a fundamental aspect of gender differences in humans.Developmental Psychobiology, 51,198 –206. doi:10.1002/dev.20358 *Lejuez, C. W., Read, J. P., Kahler, C. W., Richards, J. B., Ramsey, S. E., Stuart, G. L., . . . Brown, R. A. (2002). Evaluation of a behavioral measure of risk taking: The Balloon Analogue Risk Task (BART).

Journal of Experimental Psychology: Applied, 8,75– 84. doi:10.1037/ 1076-898X.8.2.75 *Lennings, C. J. (1991). The Schalling Sensation Seeking and Impulsivity Scales: Their relationship to time perspective and time awareness. Apreliminary report.Psychological Reports, 69,131–136. doi:10.2466/ PR0.69.5.131-136 *Lennings, C. J., & Burns, A. M. (1998). Time perspective: Temporal extension, time estimation, and impulsivity.Journal of Psychology:

Interdisciplinary and Applied, 132,367–380. doi:10.1080/ 00223989809599271 Lerner, J. S., & Keltner, D. (2000). Beyond valence: Toward a model of emotion-specific influences on judgement and choice.Cognition & Emotion, 14,473– 493. doi:10.1080/026999300402763 *Leshem, R., & Glicksohn, J. (2007). The construct of impulsivity revis- ited.Personality and Individual Differences, 43,681– 691. doi:10.1016/ j.paid.2007.01.015 Lipsey, M. W., & Wilson, D. B. (2001).Practical meta-analysis.London, England: Sage.

Llewellyn, D. J. (2008). The psychology of risk taking: Toward the integration of psychometric and neuropsychological paradigms.Ameri- can Journal of Psychology, 121,363–376. doi:10.2307/20445472 Loewenstein, G. F., Weber, E. U., Hsee, C. K., & Welch, N. (2001). Risk as feelings.Psychological Bulletin, 127,267–286. doi:10.1037/0033- 2909.127.2.267 Logan, G. D., Schachar, R. J., & Tannock, R. (1997). Impulsivity and inhibitory control.Psychological Science, 8,60 – 64. doi:10.1111/j.1467- 9280.1997.tb00545.x Longshore, D., Turner Rand, S., & Stein, J. A. (1996). Self-control in a criminal sample: An examination of construct validity.Criminology, 34, 209 –228. doi:10.1111/j.1745-9125.1996.tb01203.x *Lopez Viets, V. C. (2001). Psychosocial variables and college student gambling.Dissertation Abstracts International: Section B. Sciences and Engineering, 61(7), 3850.

*Lundahl, L. H. (1995). Separation of the effects of family history of alcoholism, heavy drinking, and gender on personality functioning and sensitivity to alcohol in college students.Dissertation Abstracts Inter- national: Section B. Sciences and Engineering, 56(5), 2874.

Lykken, D. T. (1957). A study of anxiety in the sociopathic personality.

Journal of Abnormal and Social Psychology, 55,6 –10. doi:10.1037/ h0047232 Lykken, D. T. (1995).The antisocial personalities.Hillsdale, NJ: Erlbaum.

MacDonald, K. B. (2008). Effortful control, explicit processing, and the regulation of human evolved predispositions.Psychological Review, 115,1012–1031. doi:10.1037/a0013327 MacLeod, C. M. (1991). Half a century of research on the Stroop effect: An integrative review.Psychological Bulletin, 109,163–203. doi:10.1037/ 0033-2909.109.2.163 Madden, G. J., Begotka, A. M., Raiff, B. R., & Kastern, L. L. (2003). Delay discounting of real and hypothetical rewards.Experimental and Clinical Psychopharmacology, 11,139 –145. doi:10.1037/1064-1297.11.2.139 *Magid, V., & Colder, C. R. (2007). The UPPS Impulsive Behavior Scale:

Factor structure and associations with college drinking.Personality and Individual Differences, 43,1927–1937. doi:10.1016/j.paid.2007.06.013 *Malle, B. F., & Neubauer, A. C. (1991). Impulsivity, reflection, and questionnaire response latencies: No evidence for a broad impulsivity trait.Personality and Individual Differences, 12,865– 871. doi:10.1016/ 0191-8869(91)90153-3 *Marczinski, C. A., Combs, S. W., & Fillmore, M. T. (2007). Increased sensitivity to the disinhibiting effects of alcohol in binge drinkers.

Psychology of Addictive Behaviors, 21,346 –354. doi:10.1037/0893- 164X.21.3.346 *Maydeu-Olivares, A., Rodr ´guez-Fornells, A., Go´ mez-Benito, J., & D’Zurilla, T. J. (2000). Psychometric properties of the Spanish adapta- tion of the Social Problem-Solving Inventory–Revised (SPSI–R).Per- sonality and Individual Differences, 29,699 –708. doi:10.1016/S0191- 8869(99)00226-3 Maziade, M., Boudreault, M., Thivierge, J., Cape´ raa`,P.,&Coˆte´ , R. (1984).

Infant temperament: SES and gender differences and reliability of mea- 126 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. surement in a large Quebec sample.Merrill-Palmer Quarterly, 30, 213–226.

Mazur, J. E. (1987). An adjusting procedure for studying delayed rein- forcement. In M. L. Commons, J. E. Mazur, J. A. Nevin, & H. Rachlin (Eds.),Quantitative analysis of behavior: Vol. 5. The effect of delay and intervening events on reinforcement value(pp. 55–73). Hillsdale, NJ:

Erlbaum.

*McAlister, A. R., Pachana, N., & Jackson, C. J. (2005). Predictors of young dating adults’ inclination to engage in extradyadic sexual activ- ities: A multi-perspective study.British Journal of Psychology, 96, 331–350. doi:10.1348/000712605X47936 McClure, S. M., Laibson, D. I., Loewenstein, G., & Cohen, J. D. (2004).

Separate neural systems value immediate and delayed monetary rewards.

Science, 306,503–507. doi:10.1126/science.1100907 McCrae, R. R., Terracciano, A., & 78 members of the Personality Profiles of Cultures Project. (2005). Universal features of personality traits from the observer’s perspective: Data from 50 cultures.Journal of Personality and Social Psychology, 88,547–561. doi:10.1037/0022-3514.88.3.547 *McDaniel, S. R., & Zuckerman, M. (2003). The relationship of impulsive sensation seeking and gender to interest and participation in gambling activities.Personality and Individual Differences, 35,1385–1400. doi:

10.1016/S0191-8869(02)00357-4 McLean, C. P., & Anderson, E. R. (2009). Brave men and timid women?

A review of the gender differences in fear and anxiety.Clinical Psy- chology Review, 29,496 –505. doi:10.1016/j.cpr.2009.05.003 *McLeish, K. N., & Oxoby, R. J. (2007). Measuring impatience: Elicited discount rates and the Barratt Impulsiveness Scale.Personality and Individual Differences, 43,553–565. doi:10.1016/j.paid.2007.01.002 *McMahon, S. D., & Washburn, J. J. (2003). Violence prevention: An evaluation of program effects with urban African American students.

Journal of Primary Prevention, 24,43– 62. doi:10.1023/A:

1025075617356 Meda, S. A., Stevens, M. C., Potenza, M. N., Pittman, B., Gueorguieva, R., Andrews, M. M., . . . Pearlson, G. D. (2009). Investigating the behav- ioral and self-report constructs of impulsivity domains using principal component analysis.Behavioural Pharmacology, 20,390 –399. doi:

10.1097/FBP.0b013e32833113a3 Meyer-Lindenberg, A., Buckholtz, J. W., Kolachana, B., Hariri, A. R., Pezawas, L., Blasi, G., . . . Weinberger, D. R. (2006). Neural mecha- nisms of genetic risk for impulsivity and violence in humans.Proceed- ings of the National Academy of Sciences, USA, 103,6269 – 6274.

doi:10.1073/pnas.0511311103 Miettunen, J., Veijola, J., Lauronen, E., Kantoja¨ rvi, L., & Joukamaa, M.

(2007). Sex differences in Cloninger’s temperament dimensions—A meta-analysis.Comprehensive Psychiatry, 48,161–169. doi:10.1016/ j.comppsych.2006.10.007 Milich, R., & Kramer, J. (1984). Reflections on impulsivity: An empirical investigation of impulsivity as a construct. In K. Gadow & I. Bialer (Eds.),Advances in learning and behavioral disabilities(Vol. 3, pp.

57–94). Greenwich, CT: JAI Press.

Miller, E., Joseph, S., & Tudway, J. (2004). Assessing the component structure of four self-report measures of impulsivity.Personality and Individual Differences, 37,349 –358. doi:10.1016/j.paid.2003.09.008 Mitchell, J. T., Kimbrel, N. A., Hundt, N. E., Cobb, A. R., Nelson-Gray, R. O., & Lootens, C. M. (2007). An analysis of reinforcement sensitivity theory and the five-factor model.European Journal of Personality, 21, 869 – 887. doi:10.1002/per.644 Mitchell, S. H. (1999). Measures of impulsivity in cigarette smokers and non-smokers.Psychopharmacology, 146,455– 464. doi:10.1007/ PL00005491 Mobini, S., Grant, A., Kass, A. E., & Yeomans, M. R. (2007). Relation- ships between functional and dysfunctional impulsivity, delay discount- ing and cognitive distortions.Personality and Individual Differences, 43,1517–1528. doi:10.1016/j.paid.2007.04.009Moffitt, T. E., Caspi, A., Rutter, M., & Silva, P. A. (2001).Sex differences in antisocial behaviour: Conduct disorder, delinquency, and violence in the Dunedin Longitudinal Study.Cambridge, England: Cambridge Uni- versity Press. doi:10.1017/CBO9780511490057 Mogg, K., Bradley, B. P., Dixon, C., Fisher, S., Twelftree, H., & McWil- liams, A. (2000). Trait anxiety, defensiveness and selective processing of threat: An investigation using two measures of attentional bias.

Personality and Individual Differences, 28,1063–1077. doi:10.1016/ S0191-8869(99)00157-9 Muraven, M., & Baumeister, R. F. (2000). Self-regulation and depletion of limited resources: Does self-control resemble a muscle?Psychological Bulletin, 126,247–259. doi:10.1037/0033-2909.126.2.247 Murray, K. T., & Kochanska, G. (2002). Effortful control: Factor structure and relation to externalizing and internalizing behaviors.Journal of Abnormal Child Psychology, 30,503–514. doi:10.1023/A:

1019821031523 *Nagoshi, C. T., Wood, M. D., Cote, C. C., & Abbit, S. M. (1994). College drinking game participation within the context of other predictors of alcohol use and problems.Psychology of Addictive Behaviors, 8,203– 213. doi:10.1037/0893-164X.8.4.203 Nakhaie, M. R., Silverman, R. A., & LaGrange, T. C. (2000). Self-control and social control: An examination of gender, ethnicity, class, and delinquency.Canadian Journal of Criminology, 25,35–59. doi:10.2307/ 3341910 *Neubauer, A. C. (1992). Psychometric comparison of two circadian rhythm questionnaires and their relationship with personality.Person- ality and Individual Differences, 13,125–131. doi:10.1016/0191- 8869(92)90035-N Newman, J. P., MacCoon, D. G., Vaughn, L. J., & Sadeh, N. (2005).

Validating a distinction between primary and secondary psychopathy with measures of Gray’s BIS and BAS constructs.Journal of Abnormal Psychology, 114,319 –323. doi:10.1037/0021-843X.114.2.319 Newman, J. P., Widom, C. S., & Nathan, S. (1985). Passive avoidance in syndromes of disinhibition: Psychopathy and extraversion.Journal of Personality and Social Psychology, 48,1316 –1327. doi:10.1037/0022- 3514.48.5.1316 Nigg, J. T. (2001). Is ADHD a disinhibitory disorder?Psychological Bulletin, 127,571–598. doi:10.1037/0033-2909.127.5.571 Norris, F. H., Matthews, B. A., & Riad, J. K. (2000). Characterological, situational, and behavioral risk factors for motor vehicle accidents: A prospective examination.Accident Analysis and Prevention, 32,505– 515. doi:10.1016/S0001-4575(99)00068-8 Offer, D., Ostrov, E., & Howard, K. I. (1982).The Offer Self-Image Questionnaire for Adolescents: A manual.Chicago, IL: Michael Reese Hospital.

*Overman, W. H., Frassrand, K., Ansel, S., Trawalter, S., Bies, B., & Redmond, A. (2004). Performance on the IOWA card task by adoles- cents and adults.Neuropsychologia, 42,1838 –1851. doi:10.1016/ j.neuropsychologia.2004.03.014 Pampel, F. C. (2001). Gender equality and the sex differential in mortality from accidents in high income nations.Population Research and Policy Review, 20,397– 421. doi:10.1023/A:1013307620643 Parsey, R. V., Oquendo, M. A., Simpson, N. R., Ogden, R. T., Van Heertum, R., Arango, V., & Mann, J. J. (2002). Effects of sex, age, and aggressive traits in man on brain serotonin 5-HT1A receptor binding potential measured by PET using [C-11]WAY-100635.Brain Research, 954,173–182. doi:10.1016/S0006-8993(02)03243-2 *Patock-Peckham, J. A., Hutchinson, G. T., Cheong, J., & Nagoshi, C. T.

(1998). Effect of religion and religiosity on alcohol use in a college student sample.Drug and Alcohol Dependence, 49,81– 88. doi:10.1016/ S0376-8716(97)00142-7 Patterson, C. M., & Newman, J. P. (1993). Reflectivity and learning from aversive events: Toward a psychological mechanism for the syndromes 127 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. of disinhibition.Psychological Review, 100,716 –736. doi:10.1037/ 0033-295X.100.4.716 *Patton, J. H., Stanford, M. S., & Barratt, E. S. (1995). Factor structure of the Barratt Impulsiveness Scale.Journal of Clinical Psychology, 51,768 –774.

doi:10.1002/1097-4679(199511)51:6 768::AID-JCLP2270510607 3.0.CO;2-1 Paulsen, K. A., & Johnson, M. (1980). Impulsivity: A multidimensional concept with developmental aspects.Journal of Abnormal Child Psy- chology, 8,269 –277. doi:10.1007/BF00919070 Penke, L., Denissen, J. J. A., & Miller, G. F. (2007). The evolutionary genetics of personality.European Journal of Personality, 21,549 –587.

doi:10.1002/per.629 Perkins, A. M., & Corr, P. J. (2006). Reactions to threat and personality:

Psychometric differentiation of intensity and direction dimensions of human defensive behaviour.Behavioural and Brain Research, 169, 21–28. doi:10.1016/j.bbr.2005.11.027 Piquero, A. R., & Rosay, A. B. (1998). The reliability and validity of Grasmick et al.’s self-control scale: A comment on Longshore et al.

Criminology, 36,157–174. doi:10.1111/j.1745-9125.1998.tb01244.x Plavcan, J. M. (2001). Sexual dimorphism in primate evolution.Yearbook of Physical Anthropology, 116,25–53. doi:10.1002/ajpa.10011 Plotkin, H. (1997).Darwin machines and the nature of knowledge.Cam- bridge, MA: Harvard University Press.

*Plouffe, L., & Gravelle, F. (1989). Age, sex, and personality correlates of self-actualization in elderly adults.Psychological Reports, 65,643– 647.

Porteus, S. D. (1950).The Porteus Maze Test and intelligence.Palo Alto, CA: Pacific Books.

Posner, M. I., & Rothbart, M. K. (2009). Toward a physical basis of attention and self-regulation.Physics of Life Reviews, 6,103–120. doi:

10.1016/j.plrev.2009.02.001 Pratt, T. C., & Cullen, F. T. (2000). The empirical status of Gottfredson and Hirschi’s general theory of crime: A meta-analysis.Criminology, 38, 931–964. doi:10.1111/j.1745-9125.2000.tb00911.x Quilty, L. C., & Oakman, J. M. (2004). The assessment of behavioural activation—The relationship between impulsivity and behavioural acti- vation.Personality and Individual Differences, 37,429 – 442. doi:

10.1016/j.paid.2003.09.014 *Quiroga, M. A., Herna´ ndez, J. M., Rubio, V., Shih, P. C., Santacreu, J., & Howard, V. N. (2007). Influence of impulsivity–reflexivity when testing dynamic spatial ability: Sex andgdifferences.Spanish Journal of Psychology, 10,294 –302.

Reitan, R. M. (1958). Validity of the Trail Making Test as an indicator of organic brain damage.Perceptual and Motor Skills, 8,271–276. doi:

10.2466/PMS.8.7.271-276 *Reynolds, B. (2003). Impulsivity and friends who smoke as predictors of adolescent smoking.Dissertation Abstracts International: Section B.

Sciences and Engineering, 63(12), 6122.

*Reynolds, B., Ortengren, A., Richards, J. B., & de Wit, H. (2006).

Dimensions of impulsive behavior: Personality and behavioral mea- sures.Personality and Individual Differences, 40,305–315. doi:

10.1016/j.paid.2005.03.024 *Reynolds, B., Patak, M., Shroff, P., Penfold, R. B., Melanko, S., & Duhig, A. M. (2007). Laboratory and self-report assessments of impulsive behavior in adolescent daily smokers and nonsmokers.Experimental and Clinical Psychopharmacology, 15,264 –271. doi:10.1037/1064- 1297.15.3.264 Reynolds, B., Penfold, R. B., & Patak, M. (2008). Dimensions of impulsive behavior in adolescents: Laboratory behavioral assessments.Experimen- tal and Clinical Psychopharmacology, 16,124 –131. doi:10.1037/1064- 1297.16.2.124 *Reynolds, B., Richards, J. B., & de Wit, H. (2006). Acute-alcohol effects on the Experiential Discounting Task (EDT) and a question-based mea- sure of delay discounting.Pharmacology, Biochemistry and Behavior, 83,194 –202. doi:10.1016/j.pbb.2006.01.007*Reynolds, B., Richards, J. B., Horn, K., & Karraker, K. (2004). Delay discounting and probability discounting as related to cigarette smoking status in adults.Behavioural Processes, 65,35– 42. doi:10.1016/S0376- 6357(03)00109-8 Richards, J. B., Zhang, L., Mitchell, S. H., & de Wit, H. (1999). Delay or probability discounting in a model of impulsive behavior: Effect of alcohol.Journal of the Experimental Analysis of Behavior, 71,121–143.

doi:10.1901/jeab.1999.71-121 *Rigby, K., Slee, P., & Mak, A. (1992). Impulsiveness, attitude to author- ity, and gender.Psychological Reports, 71,121–122. doi:10.2466/ PR0.71.5.121-122 *Rim, Y. (1994). Impulsivity, venturesomeness, empathy and schizotypy.

Personality and Individual Differences, 17,853– 854. doi:10.1016/0191- 8869(94)90053-1 Roberts, A. C., Robbins, T. W., & Everitt, B. J. (1988). The effects of intradimensional and extradimensional shifts on visual discrimination learning in humans and nonhuman primates.Quarterly Journal of Ex- perimental Psychology: Comparative and Physiological Psychology, 40B, 321–341.

Robinson, V. (2008).Everyday masculinities and extreme sports: Male identity and rock climbing.Oxford, England: Berg.

Rodr ´guez-Fornells, A., Lorenzo-Seva, U., & Andres-Pueyo, A. (2002).

Are high-impulsive and high risk-taking people more motor disinhibited in the presence of incentive?Personality and Individual Differences, 32, 661– 683. doi:10.1016/S0191-8869(01)00068-X Rolls, E. T. (2000). The orbitofrontal cortex and reward.Cerebral Cortex, 10,284 –294. doi:10.1093/cercor/10.3.284 Rood, L., Roelofs, J., Bögels, S., Nolen-Hoeksema, S., & Schouten, E.

(2009). The influence of emotion-focused rumination and distraction on depressive symptoms in non-clinical youth: A meta-analytic review.

Clinical Psychology Review, 29,607– 616. doi:10.1016/j.cpr.2009 .07.001 Rosenthal, R., & DiMatteo, M. R. (2001). Meta-analysis: Recent develop- ments in quantitative methods for literature reviews.Annual Review of Psychology, 52,59 – 82. doi:10.1146/annurev.psych.52.1.59 Ross, S. R., Molto´ , J., Poy, R., Segarra, P., Pastor, M. C., & Montan˜e´s, S.

(2007). Gray’s model and psychopathy: BIS but not BAS differentiates primary from secondary psychopathy in noninstitutionalized young adults.Personality and Individual Differences, 43,1644 –1655. doi:

10.1016/j.paid.2007.04.020 Rothbart, M. K. (2007). Temperament, development and personality.Cur- rent Directions in Psychological Science, 16,207–212. doi:10.1111/ j.1467-8721.2007.00505.x Rothbart, M. K., Ahadi, S. A., & Evans, D. E. (2000). Temperament and personality: Origins and outcomes.Journal of Personality and Social Psychology, 78,122–135. doi:10.1037/0022-3514.78.1.122 Rothbart, M. K., Ahadi, S. A., Hershey, K. L., & Fisher, P. (2001).

Investigations of temperament at three to seven years: The children’s behavior questionnaire.Child Development, 72,1394 –1408. doi:

10.1111/1467-8624.00355 Rothbart, M. K., & Bates, J. E. (2006). Temperament. In W. Damon, R. M.

Lerner, & N. Eisenberg (Eds.),Handbook of child psychology: Vol. 3.

Social, emotional, and personality development(6th ed., pp. 99 –166).

New York, NY: Wiley.

Rothbart, M. K., & Derryberry, D. (1981). Development of individual differences in temperament. In M. E. Lamb & A. L. Brown (Eds.), Advances in developmental psychology(Vol. 1, pp. 37– 86). Hillsdale, NJ: Erlbaum.

Rothbart, M. K., & Posner, M. I. (2006). Temperament, attention, and developmental psychopathology. In D. Cicchetti & D. Cohen (Eds.), Developmental psychopathology: Vol. 2. Developmental neuroscience (2nd ed., pp. 465–501). New York, NY: Wiley.

*Ryff, C. D., & Heincke, S. G. (1983). Subjective organization of person- 128 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. ality in adulthood and aging.Journal of Personality and Social Psychol- ogy, 44,807– 816. doi:10.1037/0022-3514.44.4.807 *Sahoo, M. K. (1985). Predictors of personality dimensions and risk-taking behaviour.Perspectives in Psychological Researches, 8,57– 62.

*Saklofske, D. H., & Eysenck, S. B. G. (1983). Impulsiveness and ven- turesomeness in Canadian children.Psychological Reports, 52,147– 152.

Schalling, D. (1978). Psychopathy-related personality variables and the psychophysiology of socialization. In R. D. Hare & D. Schalling (Eds.), Psychopathic behaviour: Approaches to research(pp. 85–106). Chich- ester, England: Wiley.

Schmitt, D. P., Realo, A., Voracek, M., & Allik, J. (2008). Why can’t a man be more like a woman? Sex differences in Big Five personality traits across 55 cultures.Journal of Personality and Social Psychology, 94,168 –182. doi:10.1037/0022-3514.94.1.168 Schulze, R. (2004).Meta-analysis: A comparison of approaches.Göttin- gen, Germany: Hogrege & Huber.

*Schweizer, K. (2002). Does impulsivity influence performance in reason- ing?Personality and Individual Differences, 33,1031–1043. doi:

10.1016/S0191-8869(01)00209-4 Shallice, T. (1982). Specific impairments of planning.Philosophical Transactions of the Royal Society of London B: Biological Sciences, 298,199 –209. doi:10.1098/rstb.1982.0082 Shepherd, J. (1990). Violent crime in Bristol: An accident and emergency department perspective.British Journal of Criminology, 30,289 –305.

Smillie, L. D. (2008). What is reinforcement sensitivity? Neuroscience paradigms for approach–avoidance process theories of personality.Eu- ropean Journal of Personality, 22,359 –384. doi:10.1002/per.674 Smith, C. L., & Hantula, D. A. (2008). Methodological considerations in the study of delay discounting in intertemporal choice: A comparison of tasks and modes.Behavior Research Methods, 40,940 –953. doi:

10.3758/BRM.40.4.940 Smith, G. T., Fischer, S., Cyders, M. A., Annus, A. M., Spillane, N. S., & McCarthy, D. M. (2007). On the validity and utility of discriminating among impulsivity-like traits.Assessment, 14,155–170. doi:10.1177/ 1073191106295527 Stanford, M. S., Mathias, C. W., Dougherty, D. M., Lake, S. L., Anderson, N. E., & Patton, J. H. (2009). Fifty years of the Barratt Impulsiveness Scale: An update and review.Personality and Individual Differences, 47,385–395. doi:10.1016/j.paid.2009.04.008 *Starrett, R. H. (1983). The conceptual commonality between impulsive- ness as a personality trait and as an ego development stage.Personality and Individual Differences, 4,265–274. doi:10.1016/0191- 8869(83)90148-4 Steinberg, L. (2007). Risk taking in adolescence: New perspectives from brain and behavioral science.Current Directions in Psychological Sci- ence, 16,55–59. doi:10.1111/j.1467-8721.2007.00475.x Stroop, J. R. (1935). Studies of interference in serial verbal reactions.

Journal of Experimental Psychology, 18,643– 662. doi:10.1037/ h0054651 Su, R., Rounds, J., & Armstrong, P. I. (2009). Men and things, women and people: A meta-analysis of sex differences in interests.Psychological Bulletin, 135,859 – 884. doi:10.1037/a0017364 Swann, A. C., Bjork, J. M., Moeller, F. G., & Dougherty, D. M. (2002).

Two models of impulsivity: Relationship to personality traits and psy- chopathology.Biological Psychiatry, 51,988 –994. doi:10.1016/S0006- 3223(01)01357-9 Swanson, M. C., Bland, R. C., & Newman, S. C. (1994). Antisocial personality disorders.Acta Psychiatrica Scandinavica, 89,63–70. doi:

10.1111/j.1600-0447.1994.tb05792.x Tangney, J. P., Baumeister, R. F., & Boone, A. L. (2004). High self-control predicts good adjustment, less pathology, better grades, and interper- sonal success.Journal of Personality, 72,271–324. doi:10.1111/j.0022- 3506.2004.00263.xTaylor, S. E., Klein, L. C., Lewis, B. P., Gruenewald, T. L., Gurung, R. A. R., & Updegraff, J. A. (2000). Biobehavioral responses to stress in females: Tend-and-befriend, not fight-or-flight.Psychological Review, 107,411– 429. doi:10.1037/0033-295X.107.3.411 Tellegen, A. (1982).Brief manual for the Differential Personality Ques- tionnaire.Unpublished manuscript, Department of Psychology, Univer- sity of Minnesota Press, Minneapolis.

*Tinius, T. P. (2003). The Intermediate Visual and Auditory Continuous Performance Test as a neuropsychological measure.Archives of Clinical Neuropsychology, 18,199 –214. doi:10.1016/S0887-6177(01)00196-2 Tittle, C. R., Ward, D. A., & Grasmick, H. G. (2003). Gender, age, and crime/deviance: A challenge to self-control theory.Journal of Research in Crime and Delinquency, 40,426 – 453. doi:10.1177/0022427803256074 *Torrubia, R., A´ vila, C., Molto´ , J., & Caseras, X. (2001). The Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ) as a measure of Gray’s anxiety and impulsivity dimensions.Personality and Individual Differences, 31,837– 862. doi:10.1016/S0191-8869(00) 00183-5 U.S. Department of Justice. (2009).Crime in the United States, 2008.

Retrieved from http://www2.fbi.gov/ucr/cius2008/data/table_42.html *van den Broek, M. D., Bradshaw, C. M., & Szabadi, E. (1992). The relationship between “impulsiveness” and hemispheric functional asym- metry, investigated with a divided visual field word recognition task.

Personality and Individual Differences, 13,355–360. doi:10.1016/0191- 8869(92)90114-5 *Verdejo-Garc ´a, A., Bechara, A., Recknor, E. C., & Pe´ rez-Garc ´a, M.

(2007). Negative emotion-driven impulsivity predicts substance depen- dence problems.Drug and Alcohol Dependence, 91,213–219. doi:

10.1016/j.drugalcdep.2007.05.025 Vigil, J. M. (2009). A socio-relational framework of sex differences in the expression of emotion.Behavioral and Brain Sciences, 32,375–390.

doi:10.1017/S0140525X09991075 Voyer, D., Voyer, S., & Bryden, M. P. (1995). Magnitude of sex differ- ences in spatial abilities: A meta-analysis and consideration of critical variables.Psychological Bulletin, 117,250 –270. doi:10.1037/0033- 2909.117.2.250 *Walderhaug, E., Magnusson, A., Neumeister, A., Lappalainen, J., Lunde, H., Refsum, H., & Landrø, N. I. (2007). Interactive effects of sex and 5-HTTLPR on mood and impulsivity during tryptophan depletion in healthy people.Biological Psychiatry, 62,593–599. doi:10.1016/ j.biopsych.2007.02.012 Wallace, J. F., Malterer, M. B., & Newman, J. P. (2009). Mapping Gray’s BIS and BAS constructs onto Factor 1 and Factor 2 of Hare’s Psychop- athy Checklist–Revised.Personality and Individual Differences, 47, 812– 816. doi:10.1016/j.paid.2009.06.019 *Weller, L. A. (2001). Cognitive inhibition and impulsivity in adult chil- dren of alcoholics and controls.Dissertation Abstracts International:

Section B. Sciences and Engineering, 61(11), 6154.

*Weyers, P., Krebs, H., & Janke, W. (1995). Reliability and construct validity of the German version of Cloninger’s Tridimensional Person- ality Questionnaire.Personality and Individual Differences, 19,853– 861. doi:10.1016/S0191-8869(95)00128-X White, J. L., Moffitt, T. E., Caspi, A., Bartusch, D. J., Needles, D. J., & Stouthamer-Loeber, M. (1994). Measuring impulsivity and examining its relationship to delinquency.Journal of Abnormal Psychology, 103, 192–205. doi:10.1037/0021-843X.103.2.192 Whiteside, S. P., & Lynam, D. R. (2001). The five factor model and impulsivity: Using a structural model of personality to understand im- pulsivity.Personality and Individual Differences, 30,669 – 689. doi:

10.1016/S0191-8869(00)00064-7 Wilding, J., Pankhania, P., & Williams, A. (2007). Effects of speed and accuracy instructions on performance in a visual search task by children with good or poor attention.British Journal of Psychology, 98,127–139.

doi:10.1348/000712606X109666 129 SEX DIFFERENCES IN IMPULSIVITY: A META-ANALYSIS This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Wilson, M., & Daly, M. (1985). Competitiveness, risk taking and violence:

The young male syndrome.Ethology and Sociobiology, 6,59 –73. doi:

10.1016/0162-3095(85)90041-X Wilson, M., & Daly, M. (1997). Life expectancy, economic inequality, homicide, and reproductive timing in Chicago neighbourhoods.British Medical Journal, 314,1271–1274.

Wood, J. L., Heitmiller, D., Andreasen, N. C., & Nopoulos, P. (2008).

Morphology of the ventral frontal cortex: Relationship to femininity and social cognition.Cerebral Cortex, 18,534 –540. doi:10.1093/cercor/ bhm079 Wood, P. B., Pfefferbaum, B., & Arneklev, B. J. (1993). Risk-taking and self-control: Social psychological correlates of delinquency.Journal of Crime and Justice, 16,111–130.

Zelenski, J. M., & Larsen, R. J. (1999). Susceptibility to affect: A com- parison of three personality taxonomies.Journal of Personality, 67, 761–791. doi:10.1111/1467-6494.00072 Zuckerman, M. (1971). Dimensions of sensation seeking.Journal of Con- sulting and Clinical Psychology, 36,45–52. doi:10.1037/h0030478 Zuckerman, M. (1979).Sensation seeking: Beyond the optimal level of arousal.Hillsdale, NJ: Erlbaum.

Zuckerman, M. (1984). Experience and desire: A new format for sensation seeking scales.Journal of Behavioral Assessment, 6,101–114. doi:

10.1007/BF01350166 Zuckerman, M. (1989). Personality in the third dimension: A psychobio- logical approach.Personality and Individual Differences, 10,391– 418.

doi:10.1016/0191-8869(89)90004-4 Zuckerman, M. (1994).Behavioral expressions and biosocial bases of sensation seeking.New York, NY: Cambridge University Press. doi:

10.1016/B0-08-043076-7/01772-1Zuckerman, M. (2007).Sensation seeking and risky behavior.Washington, DC: American Psychological Association. doi:10.1037/11555-000 Zuckerman, M., & Cloninger, C. R. (1996). Relationships between Clon- inger’s, Zuckerman’s, and Eysenck’s dimensions of personality.Person- ality and Individual Differences, 21,283–285. doi:10.1016/0191- 8869(96)00042-6 *Zuckerman, M., Eysenck, S., & Eysenck, H. J. (1978). Sensation seeking in England and America: Cross-cultural, age, and sex comparisons.

Journal of Consulting and Clinical Psychology, 46,139 –149. doi:

10.1037/0022-006X.46.1.139 Zuckerman, M., Kolin, E. A., Price, L., & Zoob, I. (1964). Development of a sensation-seeking scale.Journal of Consulting Psychology, 28,477– 482. doi:10.1037/h0040995 Zuckerman, M., & Kuhlman, D. M. (2000). Personality and risk-taking:

Common biosocial factors.Journal of Personality, 68,999 –1029. doi:

10.1111/1467-6494.00124 Zuckerman, M., & Kuhlman, D. M. (1993).Norms for the Zuckerman– Kuhlman Personality Questionnaire (ZKPQ).Unpublished manuscript, Department of Psychology, University of Delaware, Newark.

Zuckerman, M., Kuhlman, D. M., Joireman, J., Teta, P., & Kraft, M.

(1993). A comparison of three structural models for personality: The Big Three, the Big Five, and the Alternative Five.Journal of Personality and Social Psychology, 65,757–768. doi:10.1037/0022-3514.65.4.757 Received October 6, 2009 Revision received August 24, 2010 Accepted August 25, 2010 130 CROSS, COPPING, AND CAMPBELL This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.