Psychology Research Paper
Journal ol Experimental Psychology: General 1975, Vol.
104, No. 3, 268-294 Depth of Processing and the Retention of Words in Episodic Memory Fergus I. M.
Craik and Endel Tulving University of Toronto, Toronto, Ontario, Canada SUMMARY Ten experiments were designed to explore the levels of processing framework for human memory research proposed by Craik and Lockhart (1972).
The basic notions are that the episodic memory trace may be thought of as a rather auto- matic by-product of operations carried out by the cognitive system and that the durability of the trace is a positive function of "depth" of processing, where depth refers to greater degrees of semantic involvement. Subjects were induced to process words to different depths by answering various questions about the words.
For example, shallow encodings were achieved by asking questions about type- script; intermediate levels of encoding were accomplished by asking questions about rhymes; deep levels were induced by asking whether the word would fit into a given category or sentence frame.
After the encoding phase was completed, subjects were unexpectedly given a recall or recognition test for the words.
In general, deeper encodings took longer to accomplish and were associated with higher levels of performance on the subsequent memory test. Also, questions lead- ing to positive responses were associated with higher retention levels than questions leading to negative responses, at least at deeper levels of encoding.
Further experiments examined this pattern of effects in greater analytic detail.
It was established that the original results did not simply reflect differential encod- ing times; an experiment was designed in which a complex but shallow task took longer to carry out but yielded lower levels of recognition than an easy, deeper task. Other studies explored reasons for the superior retention of words associated with positive responses on the initial task.
Negative responses were remembered as well as positive responses when the questions led to an equally elaborate encoding in the two cases.
The idea that elaboration or "spread" of encoding provides a better description of the results was given a further boost by the finding of the typical pattern of results under intentional learning conditions, and where each word was exposed for 6 sec in the initial phase. While spread and elaboration may indeed be better descriptive terms for the present findings, retention depends critically on the qualitative nature of the encoding operations performed; a minimal semantic analysis is more beneficial than an extensive structural analysis.
Finally, Schulman's (1974) principle of congruity appears necessary for a complete description of the effects obtained. Memory performance is enhanced to the extent that the context, or encoding question, forms an integrated unit with the word presented.
A congruous encoding yields superior memory performance because a more elaborate trace is laid down and because in such cases the struc- ture of semantic memory can be utilized more effectively to facilitate retrieval.
The article concludes with a discussion of the broader implications of these data and ideas for the study of human learning and memory, 268 DEPTH OF PROCESSING AND WORD RETENTION 269 While information-processing models of human memory have been concerned largely with structural aspects of the system, there is a growing tendency for theorists to focus, rather, on the processes involved in learning and remembering.
Thus the theorist's task, until recently, has been to provide an adequate description of the characteristics and interrelations of the successive stages through which information flows. An al- ternative approach is to study more directly those processes involved in remembering— processes such as attention, encoding, re- hearsal, and retrieval—and to formulate a description of the memory system in terms of these constituent operations.
This alter- native viewpoint has been advocated by Cermak (1972), Craik and Lockhart (1972), Hyde and Jenkins (1969, 1973), Kolers (1973a), Neisser (1967), and Paivio (1971), among others, and it represents a sufficiently different set of fundamental assumptions to justify its description as a new paradigm, or at least a miniparadigm, in memory research.
How should we con- ceptualize learning and retrieval operations in these terms?
What changes in the sys- tem underlie remembering?
Is the "mem- ory trace" best regarded as some copy of the item in a memory store (Waugh & Nor- man, 1965), as a bundle of features (Bower, 1967), as the record resulting from the perceptual and cognitive analyses carried out on the stimulus (Craik & Lockhart, 1972), or do we remember in terms of the encoding operations themselves (Neisser, 1967; Kolers, 1973a) ?
Although we are still some way from answering these crucial questions satisfactorily, several recent stud- ies have provided important clues.
The incidental learning situation, in which subjects perform different orienting tasks, The research reported in this article was sup- ported by National Research Council of Canada Grants A8261 and A8632 to the first and second authors, respectively.
The authors gratefully acknowledge the assistance of Michael Anderson, Ed Darte, Gregory Mazuryk, Marsha Carnat, Marilyn Tiller, and Margaret Barr.
Requests for reprints should be sent to F. I. M.
Craik, Erindale College, University of Toronto, Mississauga, Ontario, LSL 1C6, Canada.
provides an experimental setting for the study of mental operations and their effects on learning.
It has been shown that when subjects perform orienting tasks requiring analysis of the meaning of words in a list, subsequent recall is as extensive and as highly structured as the recall observed under intentional conditions in the absence of any specific orienting task; further re- search has indicated that a "process" explanation is most compatible with the results (Hyde, 1973; Hyde & Jenkins, 1969, 1973; Walsh & Jenkins, 1973).
Schulman (1971) has also shown that a semantic orienting task is followed by higher retention of words than a "struc- tural" task in which the nonsemantic aspects of the words are attended to.
Similar find- ings have been reported for the retention of sentences (Bobrow & Bower, 1969; Rosen- berg & Schiller, 1971; Treisman & Tux- worth, 1974) and in memory for faces (Bower & Karlin, 1974).
In all these experiments, an orienting task requiring semantic or affective judgments led to better memory performance than tasks involving structural or syntactic judgments.
However, the involvement of semantic analyses is not the whole story:
Schulman (1974) has shown that congruous queries about words (e.g., "Is • a SOPRANO a singer?") yield better memory for the words than incongruous queries (e.g., "Is MUSTARD concave?").
Instruction to form images from the words also leads to excel- lent retention (e.g., Paivio, 1971; Sheehan, 1971).
The results of these studies have impor- tant theoretical implications.
First, they demonstrate a continuity between incidental and intentional learning—the operations carried out on the material, not the intention to learn, as such, determine retention.
The results thus corroborate Postman's (1964) position on the essential similarity of inci- dental and intentional learning, although the recent work is more usually described in terms of similar processes rather than sim- ilar responses (Hyde & Jenkins, 1973).
Second, it seems clear that attention to the word's meaning is a necessary prerequisite of good retention.
Third, since retrieval 270 FERGUS I. M.
CRAIK AND ENDEL TULVING conditions are typically held constant in the experiments described above, the dif- ferences in retention reflect the effects of different encoding operations, although the picture is complicated by the finding that different encoding operations are optimal for different retrieval conditions (e.g., Eagle & Leiter, 1964; Jacoby, 1973).
Fourth, large differences in recall under different encoding operations have been observed under conditions where the sub- jects' task does not entail organization or establishment of interitem associations; thus the results seem to take us beyond associative and organization processes, as important determinants of learning and retention.
It may be, of course, that the orienting tasks actually do lead to organiz- ation as suggested by the results of Hyde and Jenkins (1973).
Yet, it now becomes possible to entertain the hypothesis that optimal processing of individual words, qua individual words, is sufficient to support good recall. Finally, the experiments may yield some insights into the nature of learn- ing operations themselves. Classical verbal learning theory has not been much con- cerned with processes and changes within the system but has concentrated largely on manipulations of the material or the experi- mental situation and the resulting effects on learning.
Thus at the moment, we know a lot about the effects of meaningfulness, word frequency, rate of presentation, var- ious learning instructions, and the like, but rather little about the nature and character- istics of underlying or accompanying mental events. Experimental and theo- retical analysis of the effects of various encoding operations holds out the promise that intentional learning can be reduced to, and understood in terms of, some com- bination of more basic operations.
The experiments reported in the present paper were carried out to gain further in- sights into the processes involved in good memory performance.
The initial experi- ments were designed to gather evidence for the depth of processing view of mem- ory outlined by Craik and Lockhart (1972).
These authors proposed that the memory trace could usefully be regarded as the by- product of perceptual processing; just as perception may be thought to be composed of a series of analyses, proceeding from early sensory processing to later semantic- associative operations, so the resultant memory trace may be more or less elab- orate depending on the number and qualita- tive nature of the perceptual analyses car- ried out on the stimulus.
It was further suggested that the durability of the memory trace is a function of depth of processing.
That is, stimuli which do not receive full attention, and are analyzed only to a shal- low sensory level, give rise to very transient memory traces.
On the other hand, stimuli that are attended to, fully analyzed, and enriched by associations or images yield a deeper encoding of the event, and a long- lasting trace.
The Craik and Lockhart formulation provides one possible framework to accom- modate the findings from the incidental learning studies cited above.
It has the advantage of focusing attention on the pro- cesses underlying trace formation and on the importance of encoding operations; also, since memory traces are not seen as residing in one of several stores, the depth of processing approach eliminates the neces- sity to document the capacity of postulated stores, to define the coding characteristic of each store, or to characterize the mechanism by which an item is transferred from one store to another.
Despite these advantages, there are several obvious shortcomings of the Craik and Lockhart viewpoint. Does the levels of processing framework say any more than "meaningful events are well remembered" ? If not, it is simply a collec- tion of old ideas in a somewhat different setting.
Further, the position may actually represent a backward step in the study of human memory since the notions are much vaguer than any of the mathematical models proposed, for example, in Norman's (1970) collection.
If we already know that the memory trace can be precisely represented as I = (Wickelgren, 1973), then such woolly statements as "deeper processing yields a DEPTH OF PROCESSING AND WORD RETENTION 271 more durable trace" are surely far behind us.
Third, and most serious perhaps, the very least the levels position requires is some independent index of depth—there are obvious dangers of circularity present in that any well-remembered event can too easily be labeled deeply processed.
Such criticisms can be partially countered.
First, cogent arguments can be marshaled (e.g., Broadbent, 1961) for the advantages of working with a rather general theory-—• provided the theory is still capable of gen- erating predictions which are distinguish- able from the predictions of other theories.
From this general and undoubtedly true starting point, the concepts can be refined in the light of experimental results suggested by the theoretical framework.
In this sense the levels of processing viewpoint will encourage rather different types of question and may yield new insights.
A further point on the issue of general versus specific theories is that while strength theories of memory are commendably specific and so- phisticated mathematically, the sophistica- tion may be out of place if the basic premises are of limited generality or even wrong.
It is now established, for example, that the trace of an event can be readily retrieved in one environment of retrieval cues, while it is retrieved with difficulty in another (e.g., Tulving & Thomson, 1973) ; it is hard to reconcile such a finding with the view that the probability of retrieval depends only on some unidimensional strength.
With regard to an independent index of processing depth, Craik and Lockhart (1972) suggested that, when other things are held constant, deeper levels of process- ing would require longer processing times.
Processing time cannot always be taken as an absolute indicator of depth, however, since highly familiar stimuli (e.g., simple phrases or pictures) can be rapidly analyzed to a complex meaningful level.
But within one class of materials, or better, with one specific stimulus, deeper processing is assumed to require more time.
Thus, in the present studies, the time to make deci- sions at different levels of analysis was taken as an initial index of processing depth.
The purpose of this article is to describe 10 experiments carried out within the levels of processing framework.
The first experi- ments examined the-plausibility of the basic notions and attempted to rule out alterna- tive explanations of the results.
Further experiments were carried out in an attempt to achieve a better characterization of depth of processing and how it is that deeper semantic analysis yields superior memory performance.
Finally, the implications of the results for an understanding of learning operations are examined, and the adequacy of the depth of processing metaphor ques- tioned.
EXPERIMENTAL INVESTIGATIONS Since one basic paradigm is used through- out the series of studies, the method will be described in detail at this point. Variations in the general method will be indicated as each study is described.
General Method Typically, subjects were tested individually.
They were informed that the experiment con- cerned perception and speed of reaction.
On each trial a different word (usually a common noun) was exposed in a tachistoscope for 200 msec.
Before the word was exposed, the subject was asked a question about the word.
The purpose of the question was to induce the subject to pro- cess the word to one of several levels of analysis, thus the questions were chosen to necessitate processing either to a relatively shallow level (e.g., questions about the word's physical appear- ance) or to a relatively deep level (e.g., questions about the word's meaning).
In some experiments, the subject read the question on a card; in others, the question was read to him. After reading or hearing the question, the subject looked in the tachistoscope with one hand resting on a yes response key and the other on a no response key.
One second after a warning "ready" signal the word appeared and the subject recorded his (or her) decision by pressing the appropriate key (e.g., if the question was "Is the word an animal name?" and the word presented was TIGER, the subject would respond yes). After a series of such question and answer trials, the subject was unexpectedly given a retention test for the words.
The expectation was that memory performance would vary systematically with the depth of processing.
Three types of question were asked in the initial encoding phase, (a) An analysis of the physical structure of the word was effected by asking about the physical structure of the word 272 FERGUS I. M.
CRAIK AND ENDEL TULVING TABLE 1 TYPICAL QUESTIONS AND RESPONSES USED IN THE EXPERIMENTS Level of processing Answer Question Yes No Structural Phonemic Category Sentence Is the word in capital letters?
Does the word rhyme with WEIGHT?
Is the word a type of fish?
Would the word fit the sentence:
"He met a in the street"?
TABLE crate SHARK FRIEND table MARKET heaven cloud (e.g., "Is the word printed in capital letters?").
(b) A phonemic level of analysis was induced by asking about the word's rhyming characteristics (e.g., "Does the word rhyme with TRAIN?").
(c) A semantic analysis was activated by asking either categorical questions (e.g., "Is the word an animal name?") or "sentence" questions (e.g., "Would the word fit the following sentence:
The girl placed the on the table'?").
Further examples are shown in Table 1. At each of the three levels of analysis, half of the ques- tions yielded yes responses and half no responses.
The general procedure thus consisted of explaining the perceptual-reaction time task to a single subject, giving him a long series of trials in which both the type of question and yes-no decisions were randomized, and finally giving him an unexpected retention test.
This test was either free recall ("Recall all the words you have seen in the perceptual task, in any order") ; cued recall, in which some aspect of each word event was re- presented as a cue; or recognition, where copies of the original words were re-presented along with a number of distractors.
In the initial en- coding phase, response latencies were in fact recorded:
A millisecond stop clock was started by the timing mechanism which activated the tachisto- scope, and the clock was stopped by the subject's key response. Typically, over a group of sub- jects, the same pool of words was used, but each word was rotated through the various level and response combinations (CAPITALS ?-yes; SEN- TENCE ?-no, and so on).
The general prediction was that deeper level questions would take longer to answer but would yield a more elaborate mem- ory trace which in turn would support higher recognition and recall performance.
Experiment 1 Method.
In the first experiment, single subjects were given the perceptual-reaction time test; this encoding phase was followed by a recognition test.
Five types of question were used.
First, "Is there a word present?" Second, "Is the word in cap- ital letters?" Third, "Does the word rhyme with ?" Fourth, "Is the word in the cat- egory ?" Fifth, "Would the word fit in the sentence ?" When the first type of question was asked ("Is there a word pres- ent?"), on half of the trials a word was present and on half of the trials no word was present on the tachistoscope card; thus, the subject could respond yes when he detected any wordlike pat- tern on the card.
(This task may be rather dif- ferent from the others and was not used in further experiments; also, of course, it yields difficulties of analysis since no word is presented on the negative trials, these trials cannot be included in the measurement of retention.) The stimuli used were common two-syllable nouns of 5, 6, or 7 letters.
Forty trials were given; 4 words represented each of the 10 condi- tions (5 levels X yes-no).
The same pool of 40 words was used for all 20 subjects, but each word was rotated through the 10 conditions so that, for different subjects, a word was presented as a rhyme-jie.?
stimulus, a category-wo stimulus and so on.
This procedure yielded 10 combinations of questions and words; 2 subjects received each combination.
On each trial, the question was read to the subject who was already looking in the tachistoscope. After 2 sec, the word was exposed and the subject responded by saying yes or no—his vocal response activated a voice key which stopped a millisecond timer.
The experi- menter recorded the response latency, changed the word in the tachistoscope, and read the next question; trials thus occurred approximately every 10 sec.
After a brief rest, the subject was given a sheet with the 40 original words plus 40 similar dis- tractors typed on it. Any one subject had actually only seen 36 words as no word was presented on negative "Word present?" trials.
He was asked to check all words he had seen on the tachistoscope.
No time limit was imposed for this task.
Two different randomizations of the 80 recognition words were typed; one random- ization was given to each member of the pair of subjects who received identical study lists. Thus each subject received a unique presentation- recognition combination.
The 20 subjects were college students of both sexes paid for their services.
Results and discussion.
The results are shown in Table 2. The upper portion shows response latencies for the different questions. Only correct answers were in- DEPTH OF PROCESSING AND WORD RETENTION 273 eluded in the analysis.
The median latency was calculated for each subject; Table 2 shows mean medians. Although the five question levels were selected intuitively, the table shows that in fact response latency rises systematically as the questions neces- sitated deeper processing. Apart from the sentence level, yes and no responses took equivalent times.
The median latency scores were subjected to an analysis of variance (after log transformation).
The analysis showed a significant effect of level, F(4, 171) = 35.4, p < .001, but no effect of response type (yes-no) and no inter- action.
Thus, intuitively deeper questions —semantic as opposed to structural deci- sions about the word—required slightly longer processing times (150-200 msec).
Table 2 also shows the recognition re- sults. Performance (the hit rate) increased substantially from below 20% recognized for questions concerning structural charac- teristics, to 96% correct for sentence-yes decisions.
The other prominent feature of the recognition results is that the yes re- sponses to words in the initial perceptual phase were accompanied by higher sub- sequent recognition than the no responses.
Further, the superiority of recognition of yes words increased with depth (until the trend was apparently halted by a ceiling effect).
These observations were confirmed by analysis of variance on recognition pro- portions (after arc sine transformation).
Since the first level (word present?) had only yes responses, words from this level were not included in the analysis.
Type of question was a significant factor, F(3, 133) = 52.8, p < .001, as was response type (yes- no), F(\, 133) =40.2, /X.001.
The Question X Response Type interaction was also significant, F(3, 133) = 6.77, p < .001.
The results have thus shown that differ- ent encoding questions led to different re- sponse latencies; questions about the sur- face form of the word were answered com- paratively rapidly, while more abstract questions about the word's meaning took longer to answer.
If processing time is an index of depth, then words presented after a semantic question were indeed processed more deeply.
Further, the different encod- TABLE 2 INITIAL DECISION LATENCY AND RECOGNITION PERFORMANCE FOR WORDS AS A FUNCTION OF INITIAL TASK (EXPERIMENT 1) Response type Level of processing 1 2 3 4 S Response latency (msec) Yes No 591 590 614 625 689 678 711 716 746 832 Proportion recognized Yes No .22 .18 .14 .78 .36 .93 .63 .96 .83 ing questions were associated with marked differences in recognition performance:
Semantic questions were followed by higher recognition of the word.
In fact, Table 2 shows that initial response latency is sys- tematically related to subsequent recogni- tion.
Thus, within the limits of the present assumptions, it may be concluded that deeper processing yields superior retention.
It is of course possible to argue that the higher recognition levels are more simply attributable to longer study times.
This point will be dealt with later in the paper, but for the present it may be noted that in these terms, 200 msec of extra study time led to a 400% improvement in retention.
It seems more reasonable to attribute the enhanced performance to qualitative differ- ences in processing and to conclude that manipulation of levels of processing at the time of input is an extremely powerful determinant of retention of word events.
The reason for the superior recognition of yes responses is not immediately apparent— it cannot be greater depth of processing in the simple sense, since yes and no responses took the same time for each encoding ques- tion.
Further discussion of this point is deferred until more experiments are de- scribed.
Experiment 2 is basically a replication of Experiment 1 but with a somewhat tidier design and with more recognition distrac- tors to remove ceiling effects.
Experiment 2 Method.
Only three levels of encoding were used in this study: questions concerning type- 274 FERGUS I. M.
CRAIK AND ENDEL TULVING CASE RHYME SENTENCE CASE RHYME SENTENCE LEVEL OF PROCESSING FIGURE 1.
Initial decision latency and recognition performance for words as a function of the initial task (Experiment 2).
script (uppercase or lowercase), rhyme questions, and sentence questions (in which subjects were given a sentence frame with one word missing).
During the initial perceptual phase 60 questions were presented:
10 yes and 10 no questions at each of the three levels. Question type was ran- domized within the block of 60 trials.
The ques- tion was presented auditorily to the subject; 2 sec later the word appeared in the tachistoscope for 200 msec.
The subject responded as rapidly as possible by pressing one of two response keys.
After completing the 60 initial trials, the subject was given a typed list of 180 words comprising the 60 original words plus 120 distractors.
He was told to check all words he had seen in the first phase.
All words used were five-letter common con- crete nouns. From the pool Of 60 words, two question formats were constructed by randomly allocating each word to a question type until all 10 words for each question type were filled. In addition, two orders of question presentation and two random orderings of the 180-word recogni- tion list were used.
Three subjects were tested on each of the eight combinations thus generated.
The 24 subjects were students of both sexes paid for their services and tested individually.
Results and discussion.
The left-hand panel of Figure 1 shows that response latency rose systematically for both- response types, from case questions to rhyme ques- tions to sentence questions.
These data again are interpreted as showing that deeper processing took longer to accomplish.
At each level, positive and negative responses took the same time.
An analysis of variance on mean medians yielded an effect of ques- tion type, F(2, 46) = 46.5, p < .001, but yielded no effect of response type and no interaction.
Figure 1 also shows the recognition results.
For yes words, performance in- creased from 15% for case decisions to 81% for sentence decisions—more than a five- fold increase in hit rate for memory per- formance for the same subjects in the same experiment. Recognition of no words also increased, but less sharply from 19% (case) to 49% (sentence).
An analysis of vari- ance showed a question type (level of pro- cessing) effect, F(2, 46) = 118, p < .001, a response type (yes-no} effect, F(\, 23) = 47.9, p < .001, and a Question Type X Response Type interaction, F(2, 46) = 22.5, p < .001.
Experiment 2 thus replicated the results of Experiment 1 and showed clearly (a) Different encoding questions are associated with different response latencies—this find- ing is interpreted to mean that semantic questions induce a deeper level of analysis of the presented word, (b) positive and negative responses are equally fast, (c) DEPTH OF PROCESSING AND WORD RETENTION 275 recognition increases to the extent that the encoding question deals with more abstract, semantic features of the word, and (d) words given a positive response are asso- ciated with higher recognition performance, but only after rhyme and category ques- tions.
The data from Figure 1 are replotted in Figure 2, in which recognition performance is shown as a function of initial categoriza- tion time. Both yes and no functions are strikingly linear, with a steeper slope for yes responses.
This pattern of data sug- gests that memory performance may simply be a function of processing time as such (regardless of "level of analysis").
This suggestion is examined (and rejected) in this article, where we argue that level of analysis, not processing time, is the critical determinant of recognition performance.
Experiments 3 and 4 extended the gen- erality of these findings by showing that the same pattern of results holds in recall and under intentional learning conditions.
Experiment 3 Method.
Three levels of encoding were again included in the study by asking questions about typescript (case), rhyme, and sentences.
On each trial the question was read to the subject; after 2 sec the word was exposed for 200 msec on the tachistoscope.
The subject responded by press- ing the relevant response key.
At the end of the encoding trials, the subject was allowed to rest for 1 min and was then asked to recall as many words as he could.
In Experiment 3, this final recall task was unexpected—thus the initial encoding phase may be considered an incidental learning task—while in Experiment 4, subjects were informed at the beginning of the session that they would be required to recall the words.
Pilot studies had shown that the recall level in this situation tends to be low.
Thus, to boost recall, and to examine the effects of encoding level on recall more clearly, half of the words in the present study were presented twice.
In all, 48 different words were used, but 24 were pre- sented twice, making a total of 72 trials.
Of the 24 words presented once only, 4 were presented under each of the six conditions (three types of question X yes-no).
Similarly, of the 24 words presented twice, 4 were presented under each of the six conditions. When a word was repeated, it always occurred as the 20th item after its first presentation; that is, the lag between first and second presentations was held constant.
On its second appearance, the same type of question was asked as on the word's first appearance but, for '500 600 700 800 900 1000 INITIAL DECISION TIME (msec) FIGURE 2.
Proportion of words recognized as a function of initial decision time (Experiment 2).
rhyme and sentence questions, a different specific question was asked. Thus, when the word TRAIN fell into the rhyme-yes category, the question asked on its first presentation might have been "Does the word rhyme with BRAIN?" while on the second presentation the question might have been "Does the word rhyme with CRANE?" For case questions the same question was asked on the two occurrences since each subject was given the same question throughout the experiment '(e.g., "Is the word in lowercase?").
This procedure was adopted as early work had shown that sub- jects' response latencies were greatly slowed if they had to associate yes responses to both upper- case and lowercase words.
A constant pool of 48 words was used for all subjects.
The words were common concrete nouns.
Five presentation formats were constructed in which the words were randomly allocated to the various encoding conditions.
Four subjects were tested on each format:
Two made yes responses with their right hand on the right response key while two used the left-hand key for yes responses.
The 20 student subjects were paid for their services.
They were told that the experiment concerned perception and reaction time; they were warned that some words would occur twice, but they were not informed of the final recall test.
Results and discussion. Response laten- cies are shown in Table 3. For each sub- ject and each experimental condition (e.g., case-yes) the median response latency was calculated for the eight words presented on their first occurrence (i.e., the four words presented only once, and the first occurrence of the four repeated words).
The median 276 FERGUS I. M.
CRAIK AND ENDEL TULVING TABLE 3 RESPONSE LATENCIES FOR EXPERIMENTS 3 AND 4 Condition Case Rhyme Sentence 1st presentation Incidental (Exp.
3) Yes No Intentional (Exp.
4) 689 70S 816 725 870 872 Yes No 687 685 796 768 897 911 2nd presentation Incidental (Exp.
3) Yes No Intentional (Exp.
4) Yes No 616 634 609 599 689 725 684 716 771 856 793 866 Note.
Mean medians of response latencies are presented.
latency was also calculated for the four repeated words on their second presentation.
Only correct responses were included in the calculation of the medians. Table 3 shows the mean medians for the various experi- mental conditions.
There was a systematic increase in response latency from case ques- tion to sentence questions. Also, response latencies were more rapid on the word's second presentation—this was especially true for yes responses.
These observations were confirmed by an analysis of variance.
The effect of question type was significant, F(2, 38) = 14.4, p < .01, but the effect of response type was not (F < 1.0).
Repeated words were responded to reliably faster, F(l, 19) = 10.3, p < .01 and the Number of Presentations X Response Type (yes-no} interaction was significant, F(l, 19) = 5.33, p < .05.
Thus, again, deeper level questions took longer to process, but yes responses took no longer than no responses.
The extra facilitation shown by positive responses on the second presentation may be attributable to the greater predictive value of yes ques- tions.
For example, the second presenta- tion of a rhyme question may remind the subject of the first presentation and thus facilitate the decision.
Figure 3 shows the recall probabilities for words presented once or twice.
There is a marked effect of question type (sen- tence > rhymes > case); retention is again superior for words given an initial yes response and recall of twice-presented words is higher than once-presented words.
An analysis of variance confirmed these obser- vations. Semantic questions yielded higher recall, F(2, 38) = 36.9, p < .01; more yes responses than no responses were recalled, F(l, 19) = 21.4, p < .01; two presenta- tions increased performance, F(l, 19) = 33.0, p < .01.
In addition, semantically encoded words benefited more from the sec- ond presentation, as shown by the signifi- cant Question Level X Number of Presen- tations interaction, F(2, 38) = 10.8, p < .01.
Experiment 3 thus confirmed that deeper levels of encoding take longer to accomplish and that yes and no responses take equal encoding times. More important, semantic questions led to higher recall performance and more yes response words were recalled than no response words.
These basic re- sults thus apply as well to recall as they do to recognition.
Experiments 1-3 have used an incidental learning paradigm; there are good reasons to believe that the incidental nature of the task is not critical for the ob- tained pattern of results to appear (Hyde & Jenkins, 1973).
Nevertheless, it was decided to verify Hyde and Jenkins' con- clusion using the present paradigm.
Thus, Experiment 4 was a replication of Experi- ment 3, but with the difference that sub- jects were informed of the final recall task at the beginning of the session.
Experiment 4 Method.
The material and procedures were identical to those in Experiment 3 except that subjects were informed of the final free recall task. They were told that the memory task was of equal importance to the initial phase and that they should thus attempt to remember all words shown in the tachistoscope.
A 10-min period was allowed for recall.
The subjects were 20 college DEPTH OF PROCESSING AND WORD RETENTION 277 CASE RHYME SENTENCE CASE RHYME SENTENCE LEVEL OF PROCESSING FIGURE 3.
Proportion of words recalled as a function of the initial task (Experiment 3).
students, none of whom had participated in Experi- ments 1, 2, or 3.
Results and discussion.
The response latencies are shown in Table 3.
These data are very similar to those from Experiment 3, indicating that subjects took no longer to respond under intentional learning instruc- tions. Analysis of variance showed that deeper levels were associated with longer decision latencies, F(2, 38) = 27.7, p < .01, and that second presentations were re- sponded to faster, F(l, 19) = 18.9, p < .01.
No other effect was statistically reliable.
With regard to the recall results, the analysis of variance yielded significant effects of processing level, F(2, 38) = 43.4, p < .01, of repetition, F(\, 19) = 69.7, p < .01, and of response type (yes-no}, F(l, 19) = 13.9, p < .01.
In addition, the Num- ber of Presentations X Level of Processing interaction, F(2, 38) = 12.4, p < .01, and the Number of Presentations X Response Type (yes^no) interaction, F(\, 19) = 7.93, p < .025, were statistically reliable.
Figure 4 shows that these effects were attributable to superior recall of sentence decisions, twice-presented words and yes responses.
Words associated with semantic questions and with yes responses showed the greatest enhancement of recall after a second presen- tation.
To further explore the effects of inten- tional versus incidental conditions more comprehensive analyses of variance were carried out, involving the data from both Experiments 3 and 4. For the latency data, there was no significant effect of the inten- tional-incidental manipulation, nor did the intentional-incidental factor interact with any other factor. Thus, knowledge of the final recall test had no effect on subjects' decision times.
In the case of recall scores, intentional instructions yielded superior performance, F(l, 38) = 11.73, p < .01, and the Intentional-Incidental X Number of Presentations interaction was significant, F(l, 38) = 5.75, p < .05.
This latter ef- fect shows that the superiority of inten- tional instructions was greater for twice- presented items.
No other interaction in- volving the incidental-intentional factor was significant.
It may thus be concluded that the pattern of results obtained in the present 278 FERGUS I.
M.
CRAIK AND ENDEL TULVtNG CASE RHYME SENTENCE CASE RHYME SENTENCE LEVEL OF PROCESSING FIGURE 4.
Proportion of words recalled as a function of the initial task (Experiment 4).
experiments does not depend critically on incidental instructions.
The findings that intentional recall was superior to incidental recall, but that deci- sion times did not differ between intentional and incidental conditions, is at first sight contrary to the theoretical notions proposed in the introduction to this article.
If recall is a function of depth of processing and depth is indexed by decision time, then clearly differences in recall should be asso- ciated with differences in initial response latency.
However, it is possible that fur- ther processing was carried out in the inten- tional condition, after the orienting task question was answered, and was thus not reflected in the decision times.
Discussion of Experiments 1—4 Experiments 1-4 have provided empirical flesh for the theoretical bones of the argu- ment advanced by Craik and Lockhart (1972).
When semantic (deeper level) questions were asked about a presented word, its subsequent retention was greatly enhanced.
This result held for both recog- nition and recall; it also held for both inci- dental and intentional learning (Hyde & Jenkins, 1969, 1973; Till & Jenkins, 1973).
The reported effects were both robust, and large in magnitude:
Sentence-^« words showed recognition and recall levels which were superior to case-wo words by a factor ranging from 2.4 to 13.6.
Plainly, the na- ture of the encoding operation is an impor- tant determinant of both incidental and intentional learning and hence of retention.
At the same time, some aspects of the present results are clearly inconsistent with the depth of processing formulation outlined in the introduction.
First, words given a yes response in the initial task were better recalled and recognized than words given a no response, although reaction times to yes and no responses were identical.
Either reaction time is not an adequate index of depth, or depth is not a good predictor of subsequent retention.
We will argue the former case.
If depth of processing (defined loosely as increasing semantic-associative analysis of the stimulus) is decoupled from processing time, then on the one hand the independent index of depth has been lost, but on the other hand, the results of Experi- DEPTH OF" PROCESSING AND WORD RETENTION 273 rttents 1-4 can be described in terms of qualitative differences in encoding opera- tions rather than simply in terms of in- creased processing times.
The following section describes evidence relevant to the question of whether retention performance is primarily a function of "study time" or the qualitative nature of mental operations carried out during that time.
The results obtained under intentional learning conditions (Experiment 4) are also not well accommodated by the initial depth of processing notions.
If the large differences in retention found in Experi- ments 1-3 are attributable to different depths of processing in the rather literal sense that only structural analyses are acti- vated by the case judgment task, phonemic analyses are activated by rhyme judgments, and semantic analyses activated by category or sentence judgments, then surely under intentional learning conditions the subject would analyse and perceive the name and meaning of the target word with all three types of question.
In this case equal reten- tion should ensue (by the Craik and Lock- hart formulation), but Experiment 4 showed that large differences in recall were still found.
A more promising notion is that retention differences should be attributed to degrees of stimulus elaboration rather than to differ- ences in depth.
This revised formulation retains the important point (borne out by Experiments 1-4) that the qualitative na- ture .of encoding operations is critical for the establishment of a durable trace, but gets away from the notions that semantic analyses necessarily always follow structural analyses and that no meaning is involved in shallow processing tasks.
Discussion of the best descriptive frame- work for these studies will be resumed after further experiments are reported; for the moment, the term depth is retained to signify greater degrees of semantic involvement.
Before further discussions of the theoretical framework are presented, the following sec- tion describes attempts to evaluate the rela- tive effects of processing time and the qual- itative nature of encoding operations on the retention of words.
PROCESSING TIME VERSUS ENCODING OPERATIONS As a first step, the data from Experiment 2 were examined for evidence relating the effects of processing time to subsequent memory performance.
At first sight, Ex- periment 2 provided evidence in line with the notion that longer categorization times are associated with higher retention levels— Figure 2 demonstrated linear relationships between initial decision latency and sub- sequent recognition performance. How- ever, if it is processing time which deter- mines performance, and not the qualitative nature of the task, then within one task, longer processing times should be associated with superior memory performance.
That is, with the qualitative differences in pro- cessing held constant, performance should be determined by the time taken to make the initial decision.
On the other hand, if dif- ferences in encoding operations are critical for differences in retention, then memory performance should vary between orienting tasks, but within any given task, retention level should not depend on processing time.
This point was explored by analyzing the data from Experiment 2 in terms of fast and slow categorization times.
The 10 response latencies for each subject in each condition were divided into the 5 fastest responses and the 5 slowest responses. Next, mean recognition probabilities for the fast and slow subsets of words were calculated across all subjects for each condition.
The results of this analysis are shown in Figure 5; mean medians for the response latencies in each subset are plotted against recognition probabilities.
If processing time were crucial, then the words which fell into the slow subset for each task should have been recognized at higher levels than words which elicited fast responses.
Figure 5 shows that this did not happen; Slow responses were recognized little better than fast responses within each level of analysis.
On the other hand, the qualitative nature of the task continued to exert a very large effect on recognition performance, suggest- ing again that it is the nature of the encod- 280 FERGUS I. M.
CRAIK AND ENDEL TULVING I.U .9 Q UJ 8 N z |7 O 6 LJ .5 i .4 h- CC 3 § 'Z .
1 0 YES Decisions _ A - - • _„ • - i ^ NO Decisions .
- A-^4 SENTENCE • — • RHYME A D — D CASE _^-- " * — • • °~~ ^^^ — * • 1 1 1 I 1 1 1 t 500 600 700 800 900 500 600 700 INITIAL DECISION TIME (msec) 800 900 FIGURE 5.
Recognition of words as a function of task and initial decision time:
Data partitioned into fast and slow decision times (Experiment 2).
ing operations and not processing time which determines memory performance.
For both yes and no responses, slow case categorization decisions took longer than fast sentence decisions. However, words about which subjects had made sentence decisions showed higher levels of recogni- tion; 73% as opposed to 17% for yes re- sponses and 45% as opposed to 17% for no responses.
No statistical analysis was thought necessary to support the conclusion that task rather than time is the crucial aspect in these experiments. Since the point is an important one, however, a fur- ther experiment was conducted to clinch the issue. Subjects were given either a com- plex structural task or a simple semantic task to perform; it was predicted that the complex structural task would take longer to accomplish but that the semantic task would yield superior memory performance.
Experiment 5 Method.
The purpose of Experiment S was to devise a shallow nonsemantic task which was difficult to perform and would thus take longer than an easy but deeper semantic task.
In this way, further evidence on the relative contribu- tions of processing time and processing depth to memory performance could be obtained.
In both tasks, a five-letter word was shown in the tachisto- scope for 200 msec and the subject made a yes-wo decision about the word.
The nonsemantic deci- sion concerned the pattern of vowels and con- sonants which made up the word.
Where V = vowel and C = consonant, the word brain could be characterized as CCVVC, the word uncle as VCCCV, and so on.
Before each nonsemantic trial the subject was shown a card with a partic- ular consonant-vowel pattern typed on it; after studying the card as long as necessary, the sub- ject looked into the tachistoscope and the word was exposed.
The experiment was again described as a perceptual, reaction time study concerning different aspects of words and the subject was instructed to respond as rapidly as possible by pressing one of two response keys.
The seman- tic task was the sentence task from previous studies in the series.
In this case, the subject was shown a card with a short sentence typed on it; the sentence had one missing word, thus the subject's task was to decide whether the word on the tachistoscope screen would fit the sentence.
Examples of sentence-jiM trials are:
"The man threw the ball to the " (CHILD) and "Near her bed she kept a " (CLOCK).
On sentence-Mo trials an inappropriate noun from the general pool was exposed on the tachistoscope.
Again the subject responded as rapidly as pos- sible.
The subjects were not informed of the subsequent memory test.
The pool of words used consisted of 120 high frequency, concrete five-letter nouns.
Each sub- ject received 40 words on the initial decision phase of the task and was then shown all 120 words, 40 targets and 80 distractors mixed ran- domly, in the second phase.
He was then asked to recognize the 40 words he had been shown on the tachistoscope by circling exactly 40 words.
Two forms of the recognition test were typed with the same 120 words randomized differently.
In all, 24 subjects were tested in the experiment.
The pool of 120 words was arbitrarily parti- tioned into three blocks of 40 words; the first 8 subjects received one block of 40 as targets and DEPTH OF PROCESSING AND WORD RETENTION 281 the remaining 80 words served as distractors; the second 8 subjects received the second block of 40 words as targets and the third 8 subjects received the third block of 40—in all cases the remaining 80 words formed the distractor pool.
Within each group of 8 subjects who received the same 40 target words, 4 received one form of the recognition test and 4 received the other form.
Finally, within each group of 4 subjects, each word was rotated so .that it appeared (for different subjects) in all four conditions: non- semantic yes and no and semantic yes and no.
Each subject was tested individually.
After the two tasks had been explained, he was given a few practice trials, then received 40 further trials, 10 under each experimental condition.
The order of presentation of conditions was randomized.
After a brief rest period the subject was given the recognition list and told to circle exactly 40 words (those he had just seen on the tachisto- scope), guessing if necessary.
The subjects were 24 undergraduate students of both sexes, paid for their services.
Results.
The results of the experiment are straightforward.
Table 4 shows that the nonsemantic task took longer to accomplish but that the deeper sentence task gave rise to higher levels of recognition.
Decisions about consonant-vowel structure of words were substantially slower than sentence decisions'(1.7 sec as opposed to .85 sec) and this difference was significant statis- tically, F(l, 23) = 11.3, p < .01. Neither the response type (yes-no) nor the inter- action was significant.
For recognition, the analysis of variance showed that sentence decisions gave rise to higher recognition, P(\, 23) = 40.9, p < .001; yes responses were recognized better than no responses, F(l, 23) = 10.6, p < .01, but the Task X Response Type interaction was not signifi- cant.
Experiment 5 has thus confirmed the con- clusion from the reanalysis of Experiment 2; that it is the qualitative nature of the task —we argue, depth of processing—and not the amount of processing time, which deter- mines memory performance.
Figure 2 illustrates that a deep semantic task takes longer to accomplish and yields superior memory performance, but when the two factors are separated it is the task which is crucial, not processing time as such.
One constant feature of Experiments 1-4 has been the superior recall or recognition of words given a yes response in the initial TABLE 4 DECISION LATENCY AND RECOGNITION PERFORM- ANCE FOR WORDS AS A FUNCTION OF THE INITIAL TASK (EXPERIMENT 5) Response type Level of processing Structure Sentence Response latency (sec) Yes No 1.70 1.74 .83 .88 Proportion recognized Yes No .57 .50 .82 .69 perceptual phase.
This result has also been reported by Schulman (1974).
The reasons for the better retention of yes re- sponses are not immediately apparent; for example, it is not obvious that positive responses require deeper processing before the initial perceptual decision can be made.
This problem invites a closer investigation of the yes-no difference and may perhaps force a further reevaluation of the concept of depth.
POSITIVE AND NEGATIVE CATEGORIZATION DECISIONS Why are words to which positive re- sponses are made in the perceptual-decision task better remembered ? As discussed pre- viously, it does not seem intuitively reason- able that words associated with yes responses require deeper processing before the deci- sion is made.
However, if high levels of retention are associated with "rich" or "elaborate" encodings of the word (rather than deep encodings), the differences in retention between positive and negative words become understandable.
In cases where a positive response is made, the encoding question and the target word can form a coherent, integrated unit.
This integration would be especially likely with semantic questions:
for example, "A four- footed animal?" (BEAR) or "The boy met a — on the street" (FRIEND).
How- ever,, integration of the question and tar- get word would be much less likely in the negative case:
"A four-footed animal ?" 282 FERGUS I. M.
CRAIK AND ENDEL TULVING (CLOUD) or "The boy met a on the street" (SPEECH).
Greater degrees of integration (or, alternatively, greater de- grees of elaboration of the target word) may support higher retention in the sub- sequent test.
This factor of integration or congruity (Schulman, 1974) between tar- get word and question would also apply to rhyme questions but not to questions about typescript:
If the target word is in capital letters (a yes decision), the word's encod- ing would be elaborated no more than if the word had been presented in lowercase type (a no decision).
This analysis is based on the premise that effective elaboration of an encoding requires further descriptive attri- butes which (a) are salient, or applicable to the event, and (b) specify the event more uniquely. While positive semantic and rhyme decisions fit this description, neg- ative semantic and rhyme decisions and both types of case decision do not.
In line with this analysis is the finding from Experi- ments 1-4 that while positive decisions are associated with higher retention levels for semantic and rhyme questions, words elicit- ing positive and negative decisions are equally well retained after typescript judg- ments.
If the preceding argument is valid, then questions leading to equivalent elaboration for positive and negative decisions should be followed by equivalent levels of retention.
Questions which appear to meet the case are those of the type "Is the object bigger than a chair?" In this case both positive target words (HOUSE, TRUCK) and negative target words (MOUSE, PIN) should be en- coded with equivalent degrees of elabora- tion; thus, they should be equally well remembered.
This proposition was tested in Experiment 6.
Experiment 6 Method, Eight descriptive dimensions were used in the study: size, length, width, height, weight, temperature, sharpness, and value.
For each of these dimensions, a set of eight concrete nouns was generated, such that the dimension was a salient descriptive feature for the words in each set (e.g., size-ELEPHANT, MOUSE; value-DiAMOND, CRUMB).
The words were chosen to span the com- plete range of the relevant dimension (e.g., from very small to very large; very hot to very cold).
For each set an additional reference object was chosen such that half of the objects represented by the word set were "greater than" the reference ob- ject and half of the objects were "less than" the referent.
The reference object was always used in the question pertaining to that dimension; examples were "Taller than a man?" (STEEPLE- yes; CHILD-WO), "More valuable than $10?" (JEWEL-JIM; BUTTON-WO).
" Sharper than a fork?" (NEEDLE-JIM; CLUB-no).
For half of the subjects, the question was reversed in sense, so that words given a yes response by one group of subjects were given a no response by the other group. Thus, "Taller than a man?" became "Shorter than a man?" (STEEPLE-WO; CHILD- yes).
Each subject was asked questions relating to two dimensions; he thus answered 16 questions— 4 yielding positive responses and 4 yielding neg- ative responses for each dimension.
Four dif- ferent versions of the questions and targets were constructed, with two different dimensions being used in each version. Four subjects received each version—two received the original questions (e.g., "heavier than . .
." "hotter than . .
.") and two received the questions reversed ("lighter than . .
." "colder than . .
.").
Thus each subject received 16 questions; both question type and response type (yes-no) were randomized. Subjects were 16 undergraduate students of both sexes; they were paid for their services.
On each trial, the subject looked into a tachisto- scope; the question was presented auditorily, and 2 sec later the target word was exposed for 1 sec.
The subject responded by pressing the ap- propriate one of two keys.
Subjects were again told that they had to make rapid judgments about words; they were not informed of the retention test.
After completing the 16 question trials, subjects were asked to recall the target words.
Each subject was reminded of the questions he had been asked. Thus, in this study, memory was assessed in the presence of the original questions.
Results.
Again, the results are much easier to describe than the procedure.
Words given yes responses were recalled with a probability of .36, while words given no responses were recalled with a probabil- ity of .39.
These proportions did not differ significantly when tested by the Wilcoxon test. Thus, when positive and negative decisions are equally well encoded, the re- spective sets of target words are equally well recalled.
The results of this demonstration study suggest that it is not the type of response given to the presented word that is responsible for differences in subsequent recall and recognition, but rather the rich- DEPTH OF PROCESSING AND WORD RETENTION 283 ness or elaborateness of the encoding.
It is possible that negative decisions in Experi- ments 1-4 were associated with rather poor encodings of the presented words—they did not fit the encoding question and thus did not form an integrated unit with the ques- tion.
On the other hand, positive responses would be integrated with the question, and thus, arguably, formed more elaborate en- codings which supported better retention performance.
Experiment 7 was an attempt to manip- ulate encoding elaboration more directly.
Only semantic information was involved in this study.
All encoding questions were sentences with a missing word; on half of the trials the word fitted the sentence (thus all queries were congruous in Schulman's terms).
The degree of encoding elabora- tion was varied by presenting three levels of sentence complexity, ranging from very simple, • spare sentence frames (e.g., "He dropped the ") to complex, elaborate frames (e.g., "The old man hobbled across the room and picked up the valuable from the mahogany table").
The word presented was WATCH in both cases.
Al- though the second sentence is no more predictive of the word, it should yield a more elaborate encoding and thus superior memory performance.
Experiment 7 Method.
Three levels of sentence complexity were used:
simple, medium, and complex. Each subject received 20 sentence frames at each level of complexity; within each set of 20 there were 10 yes responses and 10 no responses.
The 60 encoding trials were randomized with respect to level of complexity and response type.
A constant pool of 60 words was used in the experi- ment, but two completely different sets of en- coding questions were constructed. Words were randomly allocated to sentence level and response type in the two sets (with the obvious constraint that yes and no words clearly fitted or did not fit the sentence frame, respectively).
Within each set of sentence frames, two different ran- dom presentation orders were constructed.
Five subjects were presented with each format thus generated and 20 subjects were tested in all.
The words used were common nouns. Examples of sentence frames used are: simple, "She cooked the " "The • is torn"; medium, "The frightened the children" and "The ripe tasted delicious"; complex, "The great bird swooped down and carried off the struggling " and "The small lady angrily picked up the red ." The sentence frames were written on cards and given to the subject. After studying it he looked into the tachistoscope with one hand on each response key.
After a ready signal the word was presented for 1.0 sec and the subject responded yes or no by pressing the appropriate key.
The words were exposed for a longer time in this study since the questions were more complex. Subjects were again told that the experiment was concerned with percep- tion and speed of reaction and that they should thus respond as rapidly as possible.
No mention was made of a memory test.
The 20 subjects were tested individually.
They were undergrad- uate students of both sexes, paid for their services.
After completing the 60 encoding trials, sub- jects were given a short rest and then asked to recall as many words as they could from the first phase of the experiment. They were given 8 min for free recall.
After a further rest, they were given the deck of cards containing the original sentence frames (in a new random order) and asked to recall the word associated with each sentence. Thus there were two retention tests in this study:
free recall followed by cued recall.
Results.
Figure 6 shows the results.
For free recall, there is no effect of sentence complexity in the case of no responses, but a systematic increase in recall from simple to complex in the case of yes responses.
The provision of the sentence frames as cues did not enhance the recall of no re- sponses, but had a large positive effect on the recall of yes responses; the effect of sentence complexity was also amplified in cued recall.
These observations were con- i.o .9 Q Ld .8 SIMPLE MEDIUM COMPLEX SENTENCE TYPE FIGURE 6.
Proportion of words recalled as a function of sentence complexity (Experiment 7).
(CR = cued recall, NCR = noncued recall.) 284 FERGUS I. M.
CRAIK AND ENDEL TULVING firmed by analysis of variance.
In free recall, a greater proportion of words given positive responses were recalled than those given negative responses, F(l, 19) = 18.6, p < .001; the overall effect of complexity was not significant, F(2, 38) = 2.37, p > .05, but the interaction between complexity and yes-no was reliable, F(2, 38) = 3.78, p < .05.
A further analysis, involving posi- tive responses only, showed that greater sentence complexity was reliably associated with higher recall levels, F(2, 38) = 4.44, p < .025.
In cued recall, there were sig- nificant effects of response type, F(\, 19) = 213, p < .001, complexity, F(2, 38) = 49.2, p < .001, and the Complexity X Re- sponse Type interaction, F(2, 38) = 19.2, p < .001.
An overall analysis of variance, incorporating both free and cued recall, was also carried out and this analysis revealed significantly higher performance for greater complexity, F(2, 38) = 36.5, p < .001, for positive target words, F(\, 19) = 139, p < .001, and for cued recall rela- tive to free recall, F(\, 19) = 100, p < .001.
All the interactions were significant at the p < .01 level or better; the descrip- tion of these effects is provided by Figure 6.
Experiment 7 has thus demonstrated that more complex, elaborate sentence frames do lead to higher recall, but only in the case of positive target words.
Further, the effects of complexity and response type are greatly magnified by reproviding the sen- tence frames as cues.
These results do not fit the original simple view that memory performance is deter- mined only by the nominal level of pro- cessing.
In all conditions of Experiment 7 semantic processing of the target word was necessary, yet there were still large differ- ences in performance depending on sentence complexity, the relation between target word and the sentence context, and the presence or absence of cues.
It seems that other factors besides the level of processing re- quired to make the perceptual decision are important determinants of memory perform- ance.
The notion of code elaboration provides a more satisfactory basis for describing the results.
If a presented word does not fit the sentence frame, the subject cannot form a unified image or percept of the complete sentence, the memory trace will not rep- resent an integrated meaningful pattern, and the word will not be well recalled.
In the case of positive responses, such coherent patterns can be formed and their degree of cognitive elaborateness will increase with sentence complexity. While increased elab- oration by itself leads to some increase in recall (possibly because richer sentence frames can be more readily recalled) per- formance is further enhanced when part of the encoded trace is reprovided as a cue.
It is well established that cuing aids recall, provided that the cue information has been encoded with the target word at presenta- tion and thus forms part of the same encoded unit (Tulving & Thomson, 1973).
The present results are consistent with the find- ing, but may also be interpreted as showing that a cue is effective to the extent that the cognitive system can encode the cue and the target as a congruous, integrated unit.
Elaborate cues by themselves do not aid performance even if they were presented with the target word at input, as shown by the poor recall of negative response words.
It is also necessary that the target and the cue form a coherent, integrated pattern.
Schulman (1974) reported results which are essentially identical to the results of Experiment 7. He found better recall of congruous than incongruous phrases; he also found that cuing benefited congruously encoded words much more than incongruous words. Schulman suggests that congruent words can form a relational encoding with their context, and that the context can then serve as an effective redintegrative cue at recall (Begg, 1972; Horowitz & Prytulak, 1969).
In these terms, Experiment 7 has added the finding that the semantic richness of the context benefits congruent encodings but has no effect on the encoding of incon- gruous words.
Is the concept of depth still useful in describing the present experimental results, or are the findings better described in terms of the "spread" of encoding where spread refers to the degrees of encoding elaboration or the number of encoded features?
These DEPTH OF PROCESSING AND WORD RETENTION 285 questions will be taken up in the general discussion, but in outline, we believe that depth still gives a useful account of the major qualitative shifts in a word's encod- ing (from an analysis of physical features through phonemic features to semantic prop- erties).
Within one encoding domain, how- ever, spread or number of encoded features may be better descriptions. Before grap- pling with these theoretical issues, three final short experiments will be described.
The findings from the preceding experiments were so robust that it becomes of interest to ask under what conditions the effects of differential encoding disappear.
Experi- ments 8, 9, and 10 were attempts to set boundary limits on the phenomena.
FURTHER EXPLORATIONS OF DEPTH AND ELABORATION The three studies described in this sec- tion were undertaken to examine further aspects of depth of processing and to throw more light on the factors underlying good memory performance.
The first experi- ment explored the idea that the critical dif- ference between case-encoded and sentence- encoded words might lie in the similarity of encoding operations within the group of case-encoded words.
That is, each case- encoded word is preceded by the same ques- tion, "Is the word in capital letters?", whereas each rhyme-encoded and sentence- encoded word has its own unique question.
At retrieval, it is likely that the subject uses what he can remember of the encoding question to help him retrieve the target word, Plausibly, encoding questions which were used for many target words would be less effective as retrieval cues since they do not uniquely specify one encoded event in episodic memory.
This overloading of retrieval cues would be particularly evident for case-encoded words.
It is possible to extend the argument to rhyme-encoded words also; although each target word receives a different rhyme question, pho- nemic differences may not be so unique or distinctive as semantic differences (Lock- hart, Craik, & Jacoby, 1975).
Some empirical support for these ideas may be drawn from two unpublished studies by Moscovitch and Craik (Note 1).
The first study used the same paradigm as the present series and compared cued with non- cued recall, where the cues were the original encoding questions.
It was found that cuing enhanced recall, and that the effect of cuing was greater with deeper levels of encoding.
Thus the encoding questions do help retrieval, and their beneficial effect is greatest with semantically encoded words.
The second study showed that when several target words shared the same encoding question (e.g., "Rhymes with train?" BRAIN, CRANE, PLANE; "Animal category?" LION, HORSE, GIRAFFE), the sharing manipulation had an adverse effect on cued recall. Fur- ther, the adverse effect was greatest for deeper levels of encoding, suggesting that the normal advantage to deeper levels is associated with the uniqueness of the en- coded question-target complex, and that when this uniqueness is removed, the mnemonic advantage disappears.
These ideas and findings suggest an experiment in which a case-encoded word is made more unique by being the one word in an encoding series to be encoded in this way.
In this situation the one case word might be remembered as well as a word, which, nominally, received deeper process- ing. Such an experiment in its extreme form would be expensive to conduct, in that one word forms the focus of interest.
Ex- periment 8 pursues the idea of uniqueness in a less extreme form.
Three groups of subjects each received 60 encoding trials; each trial consisted of a case, rhyme, or category question. However, each group of subjects received a different number of trials of each question type:
either 4 case, 16 rhyme, and 40 category trials; 16, 40, and 4 trials; or 40, 4, and 16 trials, respec- tively.
The prediction was that while the typical pattern of results would be found when 40 trials of one type were given, sub- sequent recognition performance would be enhanced with smaller set sizes; this en- hancement would be especially marked for the case level of encoding. 286 FERGUS I.
M.
CRAIK AND ENDEL TULVING TABLE 5 DESIGN AND RESULTS OF EXPERIMENT 8 Experimental condition Case Rhyme Yes No Yes No Category Yes No Design:
Number of trials per condition Group 1 Group 2 Group 3 2 8 20 2 8 20 8 20 2 8 20 2 20 2 8 20 2 8 Proportion recognized Group 1 Group 2 Group 3 Set size 4 Set size 16 Set size 40 .50 .51 .49 .50 .51 .49 .36 .40 .43 .36 .40 .43 .73 .66 .90 .90 .73 .66 .47 .54 .70 .70 .47 .54 .88 .95 .91 .95 .91 .88 .70 .64 .68 .64 .68 .70 Experiment 8 Method. Three groups of subjects were tested.
Group 1 received 4 case questions, 16 rhyme questions, and 40 category questions. Group 2 received 16, 40, and 4, respectively, while Group 3 received 40, 4, and 16, respectively.
At each level of encoding, half of the questions were de- signed to elicit yes responses and half no responses.
Thus each group received 60 trials; question type and response type were randomized.
The design is shown in Table 5.
The subjects were tested individually.
Each question was read by the experimenter while the subject looked in the tachistoscope; the word was exposed for 200 msec and the subject responded by pressing one of two response keys.
The sub- jects were informed that the test was a perceptual- reaction time task; the subsequent memory test was not mentioned. After completing the 60 en- coding trials, each subject was given a sheet containing the 60 target words plus 120 distrac- tors.
He was told to check exactly 60 words-— those words he had seen on the tachistoscope.
The same pool of 60 common nouns was used as targets throughout the experiment. Within each experimental group there were four pre- sentation lists; in each case Lists 1 and 2 differed only in the reversal of positive and negative deci- sions (e.g., category-jiej in List 1 became cat- egory-no in List 2).
Lsits 3 and 4 contained a fresh randomization of the 60 words, but again Lists 3 and 4 differed between themselves only in the reversal of positive and negative responses.
In all, 32 subjects were tested in the experiment; 11 each in Groups 1 and 2, and 10 in Group 3.
Two or three subjects were tested under each randomization condition.
Results.
Table 5 shows the proportion recognized by each group.
Each group shows the typical pattern of results already familiar from Experiments 1-4; there is no evidence of a perturbation due to set size.
Table 5 also shows the recognition results organized by set size; it may now be seen that set size does exert some effect, most conspicuously on rhyme-yes responses.
However, the differences previously attri- buted to different levels of encoding were certainly not eliminated by the manipula- tion of set size; in general, when set size was held constant (across groups), strong effects of question type were still found.
To recapitulate, the argument underlying Experiment 8 was that in the standard ex- periment, the encoding operation for case decisions is, in some sense, always the same; for rhyme decisions, it is somewhat similar from word to word, and is most dissimilar among words in the category task.
If the isolation effect in memory (see Cermak, 1972) is a consequence of uniqueness of encoding operations, then when similar en- codings (e.g., "case decision" words) are few in number, they should also be encoded uniquely, show the isolation effect, and thus be well recalled.
Table 5 shows that reduc- ing the number of case-encoded words from 40 to 4 did not enhance their recall, thus lack of isolation cannot account for their low retention.
On the other hand, a reduction in set size did enhance the recall of rhyme- encoded words, thus isolation effects may play some part in these experiments, although they cannot account for all aspects DEPTH OF PROCESSING AND WORD RETENTION 287 of the results. Finally, it may be of some interest that recall proportions for rhymes- Set Size 4 are quite similar to category-Set Size 40 (.90 and .70 vs. .88 and .70); this observation is at least in line with the notion that when rhyme encodings are made more unique, their recall levels are equivalent to semantic encodings.
Experiment 9: A Classroom Demonstration Throughout this series of experiments, experimental rigor was strictly observed.
Words were exposed for exactly 200 msec; great care was exercised to ensure that subjects would not inform future subjects that a memory test formed part of the ex- periment; subjects were told that the experi- ments concerned perception and reaction time; response latencies were painstakingly recorded in all cases.
One of the authors, by nature more skeptical than the other, had formed a growing suspicion that this rigor reflected superstitious behavior rather than essential features of the paradigm.
This feeling of suspicion was increased by the finding of the typical pattern of results in Experiment 9, which was conducted under intentional learning conditions. Accord- ingly, a simplified version of Experiment 2 was formulated which violated many of the rules observed in previous studies. Sub- jects were informed that the main purpose of the experiment was to study an aspect of memory; thus the final recognition test was expected and encoding was intentional rather than incidental.
Words were pre- sented serially on a screen at a 6-sec rate; during each 6-sec interval subjects recorded their response to the encoding question.
Indeed, the subjects were tested in one group of 12 in a classroom situation during a course on learning and memory; they recorded their own judgments on a question sheet and subsequently attempted to recognize the tar- get words from a second sheet. Reaction times were not measured.
The point of this study was not to attack experimental rigor, but rather to deter- mine to what extent the now familiar pat- tern of results would emerge under these much looser conditions.
If such a pattern does emerge, it will force a further examina- tion of what is meant by deeper levels of TABLE 6 PROPORTION OF WORDS RECOGNIZED FROM Two REPLICATIONS OF EXPERIMENT 9 Response type Case Rhyme Category 1st study Yes No .23 .59 .28 .33 .81 .62 2nd study Yes No .42 .37 .65 .50 .90 .65 processing and what factors underlie the superior retention of deeply processed stimuli.
Method.
On a projection screen, 60 words were presented, one at a time, for 1 sec each with a S-sec interword interval.
All subjects saw the same sequence of words, but different subjects were asked different questions about each word.
For example, if the first word was COPPER, one subject would be asked, "Is the word a metal?", a second, "Is the word a kind of fruit?", a third, "Does the word rhyme with STOPPER?", and so on.
For each word, six questions were asked (case, rhyme, category X yes-no).
During the series of 60 words, each subject received 10 trials of each question-response combination, but in a different random order.
The questions were pre- sented in booklets, 20 questions per page.
Six types of question sheet were made up, each type presented to two subjects. These sheets balanced the words across question types.
The subject studied the question, saw the word exposed on the screen, then answered the question by checking yes or no on the sheet. After the 60 encoding trials, subjects received a further sheet contain- ing 180 words consisting of the original 60 target words plus 120 distractors.
The subjects were asked to check exactly 60 words as "old." Two different randomizations of the recognition list were constructed; this control variable was crossed with the six types of question sheets. Thus each of the 12 subjects served in a unique replication of the experiment. Instructions to subjects emphasized that their main task was to remember the words, and that a recognition test would be given after the presentation phase.
The ma- terials used are presented in the Appendix.
Result.
The top of Table 6 shows that the results of Experiment 9 are quite similar to those of Experiment 2, despite the fact that in the present study subjects knew of the recognition test and words were pre- sented at the rate of 6 sec each.
The find- ing that subjects show exactly the same pat- 288 FERGUS I. M.
CRAIK AND ENDEL TULVING tern of results under these very different conditions attests to the fact that the basic phenomenon under study is a robust one.
It parallels results from Experiment 4 and previous findings of Hyde and Jenkins (1969, 1973).
Before considering the implications of Experiment 9, a replication will be mentioned.
This second experiment was a complete replication with 12 other subjects.
The results of the second study are also shown in Table 6.
Overall recog- nition performance was higher, especially with case questions, but the pattern is the same.
The results of these two studies are quite surprising. Despite intentional learning conditions and a slow presentation rate, subjects were quite poor at recognizing words which had been given shallow encod- ings. Since subjects in this experiment were asked to circle exactly 60 words, they could not have used a strict criterion of responding. Thus their low level of recog- nition performance in the case task must reflect inadequate initial registration of the information or rapid loss of registered infor- mation.
Indeed, chance performance in this task would be 33%; we have not cor- rected the data for chance in any experi- ment.
The question now arises as to why subjects do not encode case words to a deeper level during the time after their judgment was recorded.
It is possible that recognition of the less well-encoded items is somehow adversely affected by well-encoded items.
It is also possible that subjects do not know how best to prepare for a memory test and thus do no further processing of each word beyond the particular judgment that is asked.
A third hypothesis, that sub- jects were poorly motivated and thus simply did not bother to rehearse case words in a more effective way, is put to test in the final experiment.
Here subjects were paid by results; in one condition the recognition of case words carried a much higher reward than the recognition of category words.
In any event, Experiment 9 has demon- strated that encoding operations constitute an important determinant of learning or retention under a wide variety of experi- mental conditions.
The finding of a strong effect under quite loosely controlled class- room conditions, without the trappings of timers and tachistoscopes, is difficult to reconcile with the view that was implicit in the initial experiments of the series:
that processing of an item is somehow stopped at a particular level and that an additional fraction of a second would have led to bet- ter performance.
This view is therefore now rejected.
It seems to be the qualitative nature of the encoding achieved that is important for memory, regardless of how much time the system requires to reach some hypothetical level or depth of encod- ing.
Experiment 10 The final experiment to be reported was carried out to determine whether subjects can achieve high recognition performance with case-encoded words if they are given a stronger inducement to concentrate on these items. Subjects were paid for each word correctly recognized; also, they were informed beforehand that a recognition test would be given.
Correct recognition of the three types of word was differentially re- warded under three different conditions.
Subjects know that case, rhyme, and cat- egory words carried either a 1^, 3(f, or 6^ reward.
Method.
Subjects were tested under the same conditions as subjects in Experiment 9.
That is, 60 words were presented for 1 sec each plus S sec for the subject to record his judgment.
Each subject had 20 words under each encoding condition (case, rhyme, category) with 10 yes and 10 no responses in each condition.
As in Experi- ment 9, each word appeared in each encoding condition across different subjects. After the initial phase, subjects were given a recognition sheet of 180 words (60 targets plus 120 distrac- tors) and instructed to check exactly 60 words.
There were three experimental groups.
All subjects were informed that the experiment was a study of word recognition, that they would be paid according to the number of words they recognized, and therefore that they should attempt to learn each word.
The groups differed in the value associated with each class of word:
Group 1 subjects knew that they would be paid 10, 60, and 30 for case, rhyme, and category words, respectively; Group 2 subjects were paid 30, 10, and 60, respectively; and Group 3 subjects were paid 6tf, 30, and 10, respectively. These conditions are summarized in Table 7.
Thus, across groups, each class of words was associated with each reward. There were 12 undergraduate subjects in each of three groups. DEPTH OF PROCESSING AND WORD RETENTION 289 Results.
Table 7 shows that while recog- nition performance was somewhat higher than the comparable conditions of Experi- ment 9 (Table 6), the differential reward manipulation had no effect whatever.
An analysis of variance confirmed the obvious; there were significant effects due to type of encoding, F(2, 22) = 90.7, p < .01, response type (yes-no), F(l, 11) = 42.4, p < .01, and the Encoding X Response Type interaction, F(2, 22) = 4.13, p < .05, but no significant main effect or interactions involving the differential reward conditions.
Although this experiment yielded a null result, its results are not without interest.
Even when subjects were presumably quite motivated to learn and recognize case- encoded words, they failed to reach the per- formance levels associated with rhyme or category words. Subjects in Group 3 (6-3-1) reported that although they really did attempt to concentrate on case words, .
the category words were somehow "simply easier" to recognize in the second phase of the study.
Thus, Experiments 8, 9, and 10, con- ducted in an attempt to establish the bound- ary conditions for the depth of processing effect, failed to remove the strong superi- ority originally found for semantically en- coded words.
The effect is not due to iso- lation, in the simple sense at least (Experi- ment 8), it does not disappear under inten- tional learning conditions and a slow pre- sentation rate (Experiment 9), and it re- mains when subjects are rewarded more for recognizing words with shallower encod- ings (Experiment 10).
The problem now is to develop an adequate theoretical con- text for these findings and it is to this task that we now turn.
GENERAL DISCUSSION The experimental results will first be briefly summarized. Experiments 1-4 showed that when subjects are asked to make various cognitive judgments about words exposed briefly on a tachistoscope, subsequent memory performance is strongly determined by the nature of that judgment.
Questions concerning the word's meaning yielded higher memory performance than questions concerning either the word's TABLE 7 PROPORTIONS OF WORDS RECOGNIZED UNDER EACH CONDITION IN EXPERIMENT 10 Encoding operation Case Yes No Rhyme Yes No Category Yes No Mean Yes No Reward value 1 cent 3 cents 6 cents .50 .51 .73 .53 .93 .72 .72 .59 .51 .50 .73 .50 .89 .75 .71 .58 .54 .52 .69 .60 .88 .77 .70 .63 M .52 .51 .72 .54 .90 .75 .71 .60 sound or the physical characteristics of its printed form.
Further, positive decisions in the initial task were associated with higher memory performance (for more semantic questions at least) than were negative decisions.
These effects were shown to hold for recognition and recall under incidental and intentional memoriz- ing conditions.
One analysis of Experi- ment 2 showed that recognition increased systematically with initial categorization time, but a further analysis demonstrated that it was the nature of the encoding op- erations which was crucial for retention, not the amount of time as such.
Experi- ment 5 confirmed that conclusion.
Experi- ments 6 and 7 explored possible reasons for the higher retention of words given positive' responses; it was argued that en- coding elaboration provided a more satis- factory description of the results than depth of encoding. Experiment 8 showed that isolation effects could not by themselves give an account of the results, Experiment 9 demonstrated that the main findings still occurred under much looser experimental conditions, and Experiment 10 showed that the pattern of results was unaffected when differential rewards were offered for remem- bering words associated with different orienting tasks.
This set of results confirms and extends the findings of other recent investigations, 290 FERGUS I. M.
CRAIK AND ENDEL TULVING notably the series of studies by Hyde, Jenk- ins, and their colleagues (Hyde, 1973; Hyde and Jenkins, 1969, 1973; Till & Jenkins, 1973; Walsh & Jenkins, 1973) and by Schulman (1971, 1974).
It is abundantly clear that what determines the level of recall or recognition of a word event is not inten- tion to learn, the amount of effort involved, the difficulty of the orienting task, the amount of time spent making judgments about the items, or even the amount of rehearsal the items receive (Craik & Wat- kins, 1973) ; rather it is the qualitative nature of the task, the kind of operations carried out on the items, that determines retention.
The problem now is to develop an adequate theoretical formulation which can take us beyond such vague statements as "meaningful things are well remem- bered." Depth of Processing Craik and Lockhart (1972) suggested that memory performance depends on the depth to which the stimulus is analyzed.
This formulation implies that the stimulus is processed through a fixed series of ana- lyzers, from structural to semantic; that the system stops processing the stimulus once the analysis relevant to the task has been carried out, and that judgment time might serve as an index of the depth reached and thus of the trace's memorability.
These original notions now seem unsatis- factory in a number of ways.
First, the postulated series of analyzers cannot lie on a continuum since structural analyses do not shade into semantic analyses.
The modified view of "domains" of encoding (Sutherland, 1972) was suggested by Lockhart, Craik, and Jacoby (1975).
The modification postulates that while some structural analysis must precede semantic analysis, a full structural analysis is not usually car- ried out; only those structural analyses necessary to provide evidence for subsequent domains are performed.
Thus, in the case where a stimulus is highly predictable at the semantic level, only rather minimal structural analysis, sufficient to confirm the expectation, would be carried out.
The original levels of processing viewpoint is also unsatisfactory in the light of the present empirical findings if it is assumed that yes and no responses are processed to roughly the same depth before a decision can be made, since there are no differences in reaction times, yet there are large differ- ences in retention of the words.
Second, large differences in retention were also found when the complexity of the encoding context was manipulated.
Experiment 7 showed that elaborate sen- tence frames led to higher recall levels than did simple sentence frames.
This observa- tion suggests than an adequate theory must not focus only on the nominal stimulus but must also consider the encoded pattern of "stimulus in context." Third, and most crucial perhaps, strong encoding effects were found under inten- tional learning conditions in Experiments 4 and 9; it is totally implausible that, under such conditions, the system stops processing the stimulus at some peripheral level.
Unless one assumes complete perversity of subjects, it must be clear that the word is fully perceived on each trial.
Thus, dif- ferential depth of encoding does not seem a promising description, except in very gen- eral terms. Finally, as detailed earlier, initial processing time is not always a good predictor of retention. Many of the ideas suggested in the Craik and Lockhart (1972) article thus stand in need of considerable modification if that processing framework is to remain useful.
Degree of Encoding Elaboration Is spread of encoding a more satisfactory metaphor than depth?
The implication of this second description is that while a verbal stimulus is usually identified as a particular word, this minimal core encoding can be elaborated by a context of further structural, phonemic, and semantic encod- ings. Again, the memory trace can be con- ceptualized as a record of the various pat- tern-recognition and interpretive analyses carried out on the stimulus and its context; the difference between the depth and spread viewpoints lies only in the postulated orga- nization of the cognitive structures respon- sible for pattern recognition and elabora- tion, with depth implying that encoding operations are carried out in a fixed DEPTH OF PROCESSING AND WORD RETENTION 291 sequence and spread leading to the more flexible notion' that the basic perceptual core of the event can be elaborated in many different ways.
The notion of encoding domains suggested by Lockhart, Craik, and Jacoby (1975) is in essence a spread theory, since encoding elaboration depends more on the breadth of analysis carried out within each domain than on the ordinal position of an analysis in the processing sequence.
However, while spread and elaboration may indeed be better descriptive terms for the results reported in this paper, it should be borne in mind that retention depends critically on the qualitative nature of the encoding operations performed—a minimal semantic analysis is more beneficial for memory than an elaborate structural analysis (Experiment 5).
Whatever the sequence of operations, the present findings are well described by the idea that memory performance depends on the elaborateness of the final encoding.
Retention is enhanced when the encoding context is more fully descriptive (Experi- ment 7), although this beneficial effect is restricted to cases where the target stim- ulus is compatible with the context and can thus form an integrated encoded unit with it.
Thus the increased elaboration provided by complex sentence frames in Experiment 7 did'not increase recall performance in the case of negative response words.- The same argument can be applied to the generally superior retention of positive response words in all the present experiments; for positive responses the encoding question can be integrated with the target word and a more elaborate unit formed.
In certain cases, however, positive responses do not yield a more elaborately encoded unit; such cases occur when negative decisions specify the nature of the attributes in question as precisely as positive decisions.
For ex- ample, the response no to the question "Is the word in capital letters?" indicates clearly that the word is in lowercase letters; similarly a no response to the question "Is the object bigger than a man?" indicates that the object is smaller than a man. When no responses yield as elaborate an encoding as yes responses, memory performance levels are equivalent.
There is nothing inherently superior about a yes response; retention depends on the degree of elabora- tion of the encoded trace.
Several authors (e.g., Bower, 1967; Tul- ving & Watkins, 1975) have suggested that the memory trace can be described in terms of its component attributes.
This viewpoint is quite compatible with the notion of encod- ing elaboration.
The position argued in this section is that the trace may be considered the record of encoding operations carried out on the input; the function of these opera- tions is to analyze and specify the attributes of the stimulus. However, it is necessary to add that memory performance cannot be considered simply a function of the num- ber of encoded attributes; the qualitative nature of these attributes is critically im- portant.
A second equivalent description is in terms of the "features checked" during encoding.
Again, a greater number of fea- tures (especially deeper semantic features) implies a more elaborate trace.
Finally, it seems necessary to bring in the principle of integration or congruity for a complete description of encoding.
That is, memory performance is enhanced to the extent that the encoding question or context forms an integrated unit with the target word.
The higher retention of positive decision words in Schulman's (1974) study and in the present experiments can be de- scribed in this way.
The question immedi- ately arises as to why integration with the encoding context is so helpful.
One pos- sibility is that an encoded unit is unitized or integrated on the basis of past experience and, just as the target stimulus fits naturally into a compatible context at encoding, so at retrieval, re-presentation of part of the encoded unit will lead easily to regeneration of the total unit.
The suggestion is that at encoding the stimulus is interpreted in terms of the system's structured record of past learning, that is, knowledge of the world or "semantic memory" (Tulving, 1972) ; at retrieval, the information pro- vided as a cue again utilizes the structure of semantic memory to reconstruct the initial encoding.
An integrated or congruous encoding thus yields better memory per- formance, first, because a more elaborate trace is laid down and, second, because 292 FERGUS I. M.
CRAIK AND ENDEL TULVING richer encoding implies greater compatibility with the structure, rules, and organization of semantic memory.
This structure, in turn, is drawn upon to facilitate retrieval processes.
Broader Implications Finally, the implications of the present experiments and the related work reported by Hyde and Jenkins (1969, 1973), Schul- man (1971, 1974) and Kolers (1973a; Kolers & Ostry, 1974) will be briefly dis- cussed.
All these studies conform to the new look in memory research in that the stress is on mental operations; items are remembered not as presented stimuli acting on the organism, but as components of men- tal activity. Subjects remember not what was "out there" but what they did during encoding.
In more traditional memory paradigms, the major theoretical concepts were traces and associations; in both cases their main theoretical property was strength.
In turn, the subject's performance in acquisition, retention, transfer, and retrieval was held to be a direct function of the strength of asso- ciations and their interrelations.
The deter- minants of strength were also well known:
study time, number of repetitions, recency, intentionality of the subject, preexperimental associative strength between items, inter- ference by associations involving identical or similar elements, and so on. In the ex- periments we have described here, these important determinants of the strength of associations and traces were held constant:
nominal identity of items, preexperimental associations among items, intralist similarity, frequency, recency, instructions to "learn" the materials, the amount and duration of interpolated activity.
The only thing that was manipulated was the mental activity of the learner; yet, as the results showed, memory performance was dramatically affected by these activities.
This difference between the old paradigm and the new creates many interesting re- search problems that would not readily have suggested themselves in the former frame- work.
For example, to what extent are the encoding operations performed on an event under the person's volitional strategic control, and to what extent are they deter- mined by factors such as context and set?
Why are there such large differences be- tween different encoding operations?
In particular, why is it that subjects do not, or can not, encode case words efficiently when they are given explicit instructions to learn the words?
How does the ability of one list item to serve as a retrieval cue for another list item (e.g., in an A-B pair) vary as a function of encoding operations performed on the pair as opposed to the individual items?
The important concept of association as such, the bond or relation between the two items, A and B, may assume a different form in the new paradigm.
The classical ideas of frequency and recency may be eclipsed by notions referring to mental activity.
There are problems, too, associated with the development of a taxonomy of encoding operations.
How should such operations be classified ? Do encoding operations really fall into types as implied by the distinction between case, rhyme, and category in the present experiments, or is there some underlying continuity between different op- erations ?
This last point reflects the debate within theories of perception on whether analysis of structure and analysis of mean- ing are qualitatively distinct (Sutherland, 1972) or are better thought of as continuous (Kolers, 1973b).
Finally, the major question generated by the present approach is what are the encod- ing operations underlying "normal" learn- ing and remembering?
The experiments reported in this article show that people do not necessarily learn best when they are merely given "learn" instructions.
The present viewpoint suggests that when sub- jects are instructed to learn a list of items, they perform self initiated encoding opera- ions on the items.
Thus, by comparing quantitative and qualitative aspects of per- formance under learn instructions with per- formance after various combinations of in- cidental orienting tasks, the nature of learn- ing processes may be further elucidated.
The possibility of analysis and control of learning through its constituent mental op- erations opens up exciting vistas for theory and application. DEPTH OF PROCESSING AND WORD RETENTION 293 REFERENCE NOTE 1.
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Retrieval eves and levels of processing in recall and recognition.
Unpublished manuscript, 1975.
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CRAIK AND ENDEL TULVING APPENDIX Each subject in Experiment 9 received the same 60 words in the same order, but six dif- ferent "formats" were constructed, such that all six possible questions (case, rhyme, cat- egory X yes-no) were asked for each word (Table Al).
Thus, for SPEECH, the questions were (a) Is the word in capital letters?
(b) Is the word in small print?
(c) Does the word rhyme with each?
(d) Does the word rhyme with tense?
(e) Is the word a form of communication?
(f) Is the word something to wear?
Each format contained 10 questions of each type.
Negative questions were drawn from the pool of unused questions in that particular format.
TABLE Al WORDS AND QUESTIONS USED IN EXPERIMENT 9 Word SPEECH BRUSH CHEEK FENCE FLAME FLOUR HONEY KNIFE SHEEP COPPER GLOVE XMONK DAISY MINER CART CLOVE ROBBER MAST FIDDLE CHAPEL SONNET WITCH ROACH BRAKE TWIG GRIN DRILL MOAN CLAW SINGER Rhyme question each lush teak tense claim sour funny wife leap stopper shove trunk crazy liner start rove clobber past riddle grapple bonnet rich coach shake big bin fill prone raw ringer Category question a form of communication used for cleaning a part of the body found in the garden something hot used for cooking a type of food a type of weapon a type of farm animal a type of metal something to wear a type of clergy a type of flower a type of occupation a type of vehicle a type of herb a type of criminal a part of a ship a musical instrument a type of building a written form of art associated with magic a type of insect a part of a car a part of a tree a human expression a type of implement a human sound a part of an animal a type of entertainer Word BEAR LAMP CHERRY XROCK EARL POOL WEEK BOAT PAIL TROUT GRAM WOOL CLIP JUICE POND LANE NURSE LARK STATE SOAP JADE SLEET RICE TIRE CHILD DANCE FIELD FLOOR GLASS TRIBE Rhyme question hair camp very stock pearl school peak rote whale bout tram pull ship noose wand pain curse park crate rope raid feet dice fire wild stance shield sore pass scribe Category question a wild animal a type of furniture a type of fruit a type of mineral a type of nobility a type of game a division of time a mode of travel a type of container a type of fish a type of measurement a type of material a type of office supply a type of beverage a body of water a type of thoroughfare associated with medicine a type of bird a territorial unit a type of toiletry a type of precious stone a type of weather a type of grain a round object a human being a type of physical activity found in tne countryside a part of a room a type of utensil a group of people
