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Let's break this definition down and examine each key attribute to better understand what qualifies as behavior .

First, behavior is exclusively produced by an organism—only a living organism can engage in behavior .

Second, behavior represents an interaction between the organism and its environment. Third, behavior entails movement that leads to a measurable change in the environment, signifying that behavior serves a functional purpose by affecting the environment in some way.

Slide 5 First key attribute of the definition of behavior is organism.

That is, behavior can only be produced by living organisms, such as humans, dogs, fish, cats, or ants. For instance, a dog barking or a child clapping are behaviors because they involve measurable movements of a living organism interacting with its environment. In contrast, nonliving objects, like clocks ticking or smartphones making sounds, do not behave because they are nonliving objects even though they may move or create movements. Behavior is also an individual phenomenon because it is defined as an organism’ s interaction with its environment. This means only individual organisms can engage in behavior.

While we often hear the term 'group behavior,' what it actually refers to is the sum or average of the behaviors performed by individuals within the group. For example, observing a flock of birds flying together is not studying a single 'group behavior,' but rather the independent flight behaviors of individual birds. In applied behavior analysis, we focus on the interaction between environmental variables and the behavior of a single organism.

Slide 6 ASR Slide 7 Let’ s now examine the second key attribute of behavior: it is always an interaction between the or ganism and its environment. Behavior occurs when the organism actively engages with its surroundings, causing observable and measurable changes. Importantly, behavior is not a property or state of the organism.

For example, 'being sad' or ‘being anxious' are not behaviors because they describe internal states without specifying any observable action or interaction. Similarly , behavior excludes changes in the environment that happen without interaction from the organism.

For instance, 'getting wet in the rain' does not qualify as behavior because it happens passively , without the organism taking any action to produce or change the outcome. Ogden Lindsley proposed the Dead Man’s Test to help educators determine whether they are tar geting actual behavior.

The rule is simple: if a dead man can do it, then it’s not behavior.

For example, a dead man can get wet in the rain or lie still, but cannot actively raise an umbrella or walk to shelter.

These actions, such as raising an umbrella or walking, involve an interaction between the organism and its environment, which qualifies them as behavior.

Slide 8 The third key attribute of behavior is movement. Behavior is defined as the movement of some part of the organism, and this movement can occur on any scale, from large, observable actions to subtle, internal actions. For example, raising a hand to answer a question or writing notes in a journal involves obvious, visible movements. However, as Skinner pointed out, even small-scale movements—such as the slight twitch of a finger—are behaviors if they influence the environment. For a movement to qualify as behavior, it must have a function or an observable effect on the environment. This could include changes that are visible to another person or measurable by instruments. For example, turning the page of a book or opening a door has a direct, observable ef fect:

the page moves or the door swings open. These movements, even if brief, alter the environment in measurable ways. Behavior isn’t limited to overt actions—it also includes private events, which are internal movements or activities that occur within the skin and are not directly observable by others. According to Skinner, private events like thinking, feeling, or imagining are behaviors because they meet the criteria of movement and interaction with the environment, even if the environment is internal. For instance, mentally calculating the total of a shopping bill as you walk through a store or shifting your attention from one speaker to another in a conversation are examples of private events. These involve changes within the body, such as shifts in neural activity , even if no overt physical movement is visible. Private events still qualify as behavior because they can have measurable effects on the environment, such as being detected by instruments that monitor physiological activities. Slide 9 ASR Slide 10 Let’ s take a moment to distinguish between behavior and response, two fundamental concepts in applied behavior analysis. Behavior refers to a class of responses that share the same purpose or function. In other words, it’s a group of actions that achieve a common outcome. For example, greeting behavior might include waving, smiling, and saying 'hi.' These are all different responses, but they belong to the same behavior—greeting— because they serve the shared function that initiates a social interaction. On the other hand, a response involves the action of an effector , which is an organ in your body responsible for interacting with the environment. For humans, effectors include striated muscles, like your arm muscles that allow you to wave or pick up objects; smooth muscles, like those in your stomach that regulate digestion or breathing; and glands, like sweat glands that regulate your body temperature or salivary glands that help you eat. In other words, a response is a specific instance of behavior.

It’s a single, discrete action that occurs at a given moment in time. For example, waving your hand to say hello is one specific response within the broader class of greeting behavior.

Smiling when you meet someone is another specific response in that same class. Each response is an individual occurrence of behavior .

Slide 11 ASR Slide 12 Now let’s talk about describing behavior by its form, or what we call response topography.

Response topography refers to the physical shape or form of a behavior.

For example, consider someone opening a jar.

You might describe the specific hand and finger movements they use to twist the lid. However, the topography of these movements will vary slightly each time. Two instances of opening a jar may not be the same, but the overall function—removing the lid to access what’s inside—remains consistent. While it can be useful to describe behavior by its form, behavior analysis typically emphasizes function over form. This means we focus on what a behavior accomplishes, not just how it looks. The same behavior can take many forms but still serve the same purpose. This brings us to the concept of response classes. A response class includes all the responses that produce the same environmental effect.

For example, let’s say a person wants to gain someone’s attention. They might wave their hand, say 'Excuse me,' or tap the person on the shoulder.

These responses look very different in form, but they all belong to the same response class because they serve the same function: getting someone’s attention. This functional perspective is also important because two responses with the same topography can have completely different functions. For example, a child crying could have different functions depending on the environmental contingencies. In one situation, crying might serve to gain attention from a caregiver, such as being comforted. In another, crying might serve to escape an aversive situation, such as avoiding a difficult homework assignment. Although the crying looks the same in both cases, its functions are different and defined by the environment variables that control it. By focusing on function over form, behavior analysis allows us to understand why behaviors occur , rather than just describing how they look. This functional approach helps us identify how behavior functions on the environment and allow us develop effective interventions based on the function of behavior.

Slide 13 The term repertoire is used in at least two ways. First, it can refer to the entire set of behaviors a person is capable of performing. In this sense, a person’s repertoire encompasses everything they can do, from speaking and walking to problem-solving and playing sports. However , more often, the term repertoire refers to a specific collection of knowledge and skills that are relevant to particular settings or tasks. This means that people have different repertoires for different aspects of their lives, and these repertoires guide how they behave in various situations. For example, you likely have a repertoire of behaviors that you use in informal social settings, such as hanging out with friends, and this differs from the repertoire you use in formal settings, like a job interview or a meeting. While the informal repertoire might include joking and casual language, the formal repertoire likely includes more reserved speech and professional body language. Additionally , we all develop repertoires in specific domains. For instance, you might have a repertoire related to language skills, which includes speaking, writing, and understanding grammar .

You might also have a repertoire for academic tasks, such as taking notes, or solving math problems. Other repertoires could include behaviors related to recreation, like playing a musical instrument, or everyday routines, like cooking or cleaning. What’ s important is that repertoires are learned. Through practice and experience, we develop and refine these skills to meet the demands of our environment. Slide 14 ASR Slide 15 Now , let’s look at the concepts of stimulus and stimulus class. Slide 16 Before we start discussing stimulus and stimulus class, it’s important to first address the concept of the environment. Stimuli that affect human behavior exist within the environment—and so does behavior itself. All behavior occurs within an environmental context; it cannot happen in a vacuum. Behavior is always influenced by the conditions surrounding it, and understanding this relationship is fundamental to behavior analysis. Johnston and Pennypacker define the environment as the full set of physical circumstances in which the organism exists. This definition is both comprehensive and specific. It’s comprehensive because any aspect of the physical world can influence behavior, from light levels to sounds, smells, or other people’s actions. At the same time, it’s specific because, for any given behavior , we focus only on those environmental factors that are functionally related to the behavior .

In other words, behavior analysts identify and study the specific stimuli that directly influence individual responses. Importantly , the environment doesn’t stop at the surface of the skin. The organism’ s body is also part of the environment, particularly in relation to behaviors that involve internal events. For example, when you scratch an itch, the sensation of itching—arising from within your body—acts as an antecedent. The relief you feel after scratching functions as a negative reinforcer , increasing the likelihood that you will scratch again under similar circumstances. This illustrates that our own bodies provide ongoing sources of both antecedent and consequent stimuli, making the distinction between ‘inside’ and ‘outside’ the skin less important than it might initially seem. The environment is not static—it’s a dynamic and constantly changing. Because of this, behavior analysts describe specific aspects of the environment in terms of stimulus conditions or events. Stimuli are the parts of the environment that interact with behavior, and analyzing these relationships helps us understand why behavior happens and how it can be influenced. Slide 17 A stimulus is an energy change in the environment that affects an organism through its receptor cells. In simple terms, it is anything in the environment—internal or external—that causes an ener gy change, such as light, sound, or pressure, and interacts with the organism’ s sensory systems, allowing the organism to detect it. Humans detect stimuli using different receptor systems. First, there are exteroceptors, which detect stimuli from outside the body.

These include the sense organs responsible for vision, hearing, smell, taste, and touch. For example, seeing a flashing light, hearing a car honking, or feeling the rough texture of sandpaper all involve exteroceptors. Next, we have interoceptors, which are sensitive to stimuli originating inside the body.

These receptors detect things like a stomach ache, feelings of hunger, or other internal discomforts. Lastly, there are proprioceptors, which provide information about movement and balance. These receptors help you sense the position of your body parts in space. For instance, you know where your arm is as you reach for a glass without needing to look at it, or you maintain balance when walking on uneven terrain. Behavior analysts primarily focus on external stimuli—those detected by exteroceptors—because they are more accessible for observation and manipulation. For example, we might study how a child learns to respond to the sound of a school bell or to the visual cue of a teacher raising their hand. These external stimuli are key features of the physical and social environments where behavior occurs. Here’ s an important point: behavior is not influenced by static or unchanging conditions in the environment. Instead, behavior is driven by energy changes—transitions from one state to another .

When we talk about the presentation of a stimulus, we are really referring to the moment of change—the appearance of that stimulus. For example, consider a phone ringing. It is not the static presence of the phone that evokes the response of picking it up, but the change—the sudden ringing—that triggers the behavior.

So why do we focus on change? First, it is the dynamic changes in the environment that influence behavior.

People respond to events such as a light turning on or a doorbell ringing, rather than static conditions in the environment. Second, focusing on these changes helps us analyze complex phenomena more effectively . For example, in a classroom, it is not the teacher ’s static presence that influences students’ behavior, but specific actions, like clapping hands, that capture their attention and redirect their focus. Finally , it’s important to note that not all stimuli will affect behavior.

Just because an energy change occurs and is detected does not mean it will elicit a response. For example, a neutral stimulus, like a constant, faint background sound with no meaning or significance, might not evoke any behavior at all. Slide 18 ASR Slide 19 Dif ferent stimuli that share common characteristics may form a stimulus class. A stimulus class is a group of stimuli that share a common set of features, which can be based on one or more dimensions: formal, temporal, or functional. By grouping stimuli into classes, behavior analysts can better understand how various stimuli influence behavior, even when the stimuli may look dif ferent or occur under different circumstances. Now , let’s explore the three dimensions of stimuli that help define stimulus classes. The first dimension is the formal dimension, which focuses on the physical characteristics of stimuli. These characteristics include properties like size, color, intensity, weight, and spatial position. For instance, a stimulus class based on formal dimensions might include all objects that are red, such as a red ball, a red book, and a red light. Stimuli can also be categorized as nonsocial, such as the sound of a bell or the flashing of a light, or as socially mediated, like someone asking, 'Can you help me?' or offering, 'Want some peanuts?' The second dimension is the temporal dimension, which considers when a stimulus occurs in relation to behavior.

Behavior is most influenced by stimulus changes that happen either before or after the behavior.

Stimuli that occur before the behavior are called antecedents. For example, if a teacher tells students, 'Anyone who finishes the test early gets extra playtime,' that statement functions as an antecedent. Antecedents can also include environmental factors, such as lighting, temperature, or the arrangement of chairs in a room, as long as they occur prior to the specific behavior of interest. Stimuli that occur after a behavior are called consequences. Not all consequences affect behavior , but those that are relevant to the individual’s current motivation and occur soon after the behavior can significantly influence whether the behavior is likely to happen again in the future. For example, if a student answers a question correctly and the teacher provides praise or a golden star, the praise and golden star both serve as reinforcing consequences, increasing the likelihood that the student will answer questions in the future. Finally , we have the functional dimension, which focuses on the effects that stimuli have on behavior .

Stimuli in this dimension are categorized by their influence on current behavior and their potential to shape future behavior.

For example, antecedent stimulus conditions such as dif ferent task instructions increase current behavior temporarily.

In contrast, consequential stimulus conditions such as different reinforcers have a more lasting effect on behavior by increasing the likelihood of that behavior occurring again in the future. Slide 20 ASR Slide 21 Now , we will discuss conditioning, which is another term for learning. Most of our behaviors are acquired through two fundamental processes: respondent conditioning, which involves learning through associations, and operant conditioning, which involves learning through consequences. Slide 22 There are two primary sources of behavior: phylogeny and ontogeny .

Phylogeny refers to the evolutionary history of a species, where behaviors develop across generations as a result of natural selection. These behaviors are hardwired into organisms because they enhance survival and reproduction. For example, responses like pulling your hand away from a hot surface or blinking in response to a sudden bright light are phylogenic behaviors. These are unconditioned, or unlearned, responses. They are automatic, innate behaviors that occur without prior learning, shaped by the long evolutionary history of the species. In contrast, ontogeny refers to an individual’s unique learning history.

While phylogeny focuses on inherited behaviors that are universal to the species, ontogeny is about the behaviors acquired over a lifetime through interaction with the environment. These are learned behaviors, shaped by experiences and various types of conditioning. For example, a child might learn to raise their hand in class to gain the teacher’s attention. This behavior is not innate or inherited—it emerges as a result of personal experiences and operant conditioning. Slide 23 A fundamental type of behavior is respondent behavior, which refers to responses that are elicited by specific antecedent stimuli. For instance, if you touch a hot surface, the heat elicits the reflexive response of pulling your hand away.

Similarly, a sudden loud noise can elicit an automatic increase in your heart rate. These behaviors occur in direct response to specific antecedent stimuli, and the presence of the antecedent stimulus alone is sufficient to elicit these responses. It’ s important to note that both examples involve unconditioned responses—behaviors that occur naturally in response to unconditioned stimuli, such as heat or a loud sound. This relationship between an unconditioned stimulus and an unconditioned response is known as an unconditioned reflex, which is determined by the phylogenic history of our species. Slide 24 In respondent behavior, learning occurs through respondent conditioning, also known as classical or Pavlovian conditioning. This is a learning process where a stimulus that initially doesn’t elicit a reaction—something we call a neutral stimulus—comes to elicit a response after being paired with a stimulus that naturally elicits that response. T o understand this, let’s go step by step using Pavlov’s experiment with dogs. Before any learning happens, Pavlov noticed a unconditioned reflex in the dogs. When food was placed in their mouths, the dogs would salivate automatically.

This is what we call an unconditioned reflex, because it happens naturally, without any learning. In this reflex: the food is the unconditioned stimulus because it naturally causes the salivation; the salivation is the unconditioned response because it’s the natural reaction to the food. At the same time, Pavlov introduced a sound—a ticking metronome—that the dogs initially ignored. This sound is called a neutral stimulus because it didn’t elicit any salivation or other response on its own. Next, Pavlov paired the neutral stimulus (the metronome) with the unconditioned stimulus (the food). Here’s what he did: every time he started the metronome, he immediately followed it by presenting food to the dogs. This pairing process was repeated several times. After several pairings, something interesting happened. The dogs began to salivate as soon as they heard the sound of the metronome, even when no food was presented. At this point, the metronome was no longer a neutral stimulus—it had become a conditioned stimulus because it now triggered salivation on its own. The salivation in response to the metronome became a conditioned response because it was a learned behavior.

So, what happened here? Through the process of pairing, the dogs learned to associate the sound of the metronome with the presentation of food. The metronome, which initially had no meaning to the dogs, became a signal for food and started to elicit salivation. Let’ s summarize the key elements of respondent conditioning: Unconditioned stimulus: This is something that naturally causes a reaction, like food causing salivation; Unconditioned response: This is the natural reaction to the unconditioned stimulus, like salivating when food is presented; Neutral stimulus: This is something that initially doesn’t cause any reaction, like the sound of the metronome before the pairing; Conditioned stimulus: This is the previously neutral stimulus that, after being paired with the unconditioned stimulus, now causes a response, like the metronome after learning; Conditioned response: This is the learned reaction to the conditioned stimulus, like salivating in response to the sound of the metronome. Slide 25 ASR Slide 26 Let’ s discuss the second fundamental type of learning: operant conditioning. Operant conditioning refers to how the consequences of a behavior determine whether that behavior is more or less likely to happen again in the future. T o understand this, let’s break it down. A consequence is anything that happens after a behavior, and it can either increase or decrease the likelihood of that behavior occurring again in similar circumstances: If a consequence increases the behavior, we call it reinforcement. For example, imagine a baby cries when they are hungry and is then fed as a result of crying. Because the crying led to food, the baby is more likely to cry again the next time they are hungry.

On the other hand, a punisher is a consequence that decreases the behavior it follows. For instance, if a baby cries when hungry but gets yelled at as a consequence, and the baby finds yelling aversive, they may cry less in the future. Now , let’s explore some important points about operant conditioning. First, consequences don’t change the behavior that’s already happened—they only influence whether similar behaviors will occur again in the future. For example, if a child says 'thank you' and their parent praises them, the praise doesn’t change the fact that the child already said 'thank you.' However , the praise makes it more likely that the child will say 'thank you' again in the future. This is why we say that consequences only affect future behavior.

Second, when we say that reinforcement strengthens a behavior, we don’t mean it strengthens just one specific action. Instead, it strengthens an entire response class—a group of responses that achieve the same outcome. For example, if a baby whines or cries and both behaviors lead to food, these responses belong to the same response class because they both produce the same result—getting fed. Operant conditioning strengthens or weakens both behaviors, not just one specific behavior .

Third, timing is critical in operant conditioning. Immediate consequences have the strongest ef fect on behavior.

For example, if you give a dog a treat right after it sits, sitting is reinforced. But if you wait a minute before giving the treat, the reinforcement is much less effective.

The closer the consequence follows the behavior, the stronger the effect on learning—this is called contiguity .

Importantly , operant conditioning strengthens or weakens any behavior that happens immediately before a consequence, even if the behavior seems unrelated. For example, a poker player might tap their cards in a peculiar way because, in the past, this behavior was followed by a winning hand. Tapping the cards has no actual effect on the outcome of the game, but because it occurred just before reinforcement, it becomes strengthened. This is called superstitious behavior and highlights how timing—not logic—determines which behaviors are selected by reinforcement or punishment. Fourth, it’s important to understand that operant conditioning occurs automatically. A person or animal does not need to consciously aware, recognize, or understand that their behavior is being reinforced or punished for learning to occur.

For example, a toddler might learn to pull on a dog’ s leash to get the dog’s attention, even without realizing why this behavior works. Conditioning happens regardless of awareness. These behaviors that are learned through consequences are called operant behaviors. In contrast, behaviors learned through the association of antecedents are called respondent behaviors. Slide 27 ASR