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8/7/2019 Todo sobre memoria

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Journal of Experimental Psychology: General1975, Vol. 104, No. 3. 268-294

Depth of Processing and the Retention of Words inEpisodic Memory

Fergus I. M. Craik and Endel TulvingUniversity of Toronto, Toronto, Ontario, Canada

SUMMARY

Ten experiments were designed to explore the levels of processing frameworkfor human memory research proposed by Craik and Lockhart (1972). The basicnotions 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 thedurability of the trace is a positive function of "depth" of processing, where depthrefers to greater degrees of semantic involvement. Subjects were induced toprocess 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 intoa given category or sentence frame. After the encoding phase was completed,subjects were unexpectedly given a recall or recognition test for the words. Ingeneral, deeper encodings took longer to accomplish and were associated withhigher levels of performance on the subsequent memory test. Also, questions lead-ing to positive responses were associated with higher retention levels than questionsleading 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 tooklonger to carry out but yielded lower levels of recognition than an easy, deepertask. Other studies explored reasons for the superior retention of words associatedwith positive responses on the initial task. Negative responses were rememberedas well as positive responses when the questions led to an equally elaborate encodingin the two cases. The idea that elaboration or "spread" of encoding provides abetter description of the results was given a further boost by the finding of thetypical pattern of results under intentional learning conditions, and where each

word was exposed for 6 sec in the initial phase. While spread and elaborationmay indeed be better descriptive terms for the present findings, retention dependscritically on the qualitative nature of the encoding operations performed; aminimal semantic analysis is more beneficial than an extensive structural analysis.

Finally, Schulman's (1974) principle of congruity appears necessary for acomplete description of the effects obtained. Memory performance is enhancedto the extent that the context, or encoding question, forms an integrated unit withthe word presented. A congruous encoding yields superior memory performancebecause 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 dataand ideas for the study of human learning and memory.

268


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DEPTH OF PROCESSING AND WORD RETENTION 269

While information-processing models ofhuman memory have been concerned

largely with structural aspects of thesystem, there is a growing tendency fortheorists to focus, rather, on the processes

involved in learning and remembering.

Thus the theorist's task, until recently, hasbeen to provide an adequate description ofthe characteristics and interrelations of thesuccessive stages through whichinformation flows. An alternative approachis to study more directly those processes

involved in remembering processes suchas attention, encoding, rehearsal, andretrievaland to formulate a description ofthe memory system in terms of theseconstituent operations. This alternativeviewpoint has been advocated by Cermak(1972), Craik and Lockhart (1972), Hydeand Jenkins (I960, 1973). Kolers (1973a),Neisser (1967), and Paivio (1971), amongothers, and it represents a sufficiently

different set of fundamental assumptions tojustify its description as a new paradigm,or at least a miniparadigm, in memoryresearch. How should we conceptualizelearning and retrieval operations in theseterms? What changes in the systemunderlie remembering? Is the "mem-ory trace" best regarded as some copy ofthe item in a memory store (Waugh & Nor-man, 1965), as a bundle of features

(Bower, 1967), as the record resulting fromthe perceptual and cognitive analysescarried out on the stimulus (Craik &Lockhart, 1972), or do we remember interms of the encoding operationsthemselves (Neisser, 1967; Kolers, 1973a)?Although we are still some way fromanswering these crucial questionssatisfactorily, several recent studies haveprovided important clues.

The incidental learning situation, inwhich subjects perform differento ri en ting t asks ,

_________________________

The research reported in this article was sup-ported by National Research Council of CanadaGrants A8261 and A8632 to the first and secondauthors, respectively. The authors gratefullyacknowledge 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, L5L 1C6, Canada.

provides an experimental setting for thestudy of mental operations and their effectson learning. It has been shown that whensubjects 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 observedunder intentional conditions in the absenceof any specific orienting task; further re-search has indicated that a "process"explanation is most compatible with theresults (Hyde, 1973; Hyde & Jenkins,1969, 1973; Walsh & Jenkins, 1973).Schulman (1971) has also shown that a

semantic orienting task is followed byhigher retention of words than a "struc-tural" task in which the nonsemantic aspectsof the words are attended to. Similar find-ings have been reported for the retention ofsentences (Bobrow & Bower, 1969; Rosen-berg & Schiller, 1971; Treisman & Tux-worth, 1974) and in memory for faces

(Bower & Karlin, 1974). In all theseexperiments, an orienting task requiring

semantic or affective judgments led tobetter memory performance than tasksinvolving structural or syntactic judgments.However, the involvement of semanticanalyses is not the whole story: Schulman(1974) has shown that congruous queriesabout words (e.g., "Is a SOPRANO asinger?"') yield better memory for thewords than incongruous queries (e.g., "IsMUSTARD 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, theydemonstrate a continuity between incidental

and intentional learningthe 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


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270 FERGUS I. M. CRAIK AND ENDEL TULVING

conditions are typically held constant inthe experiments described above, the dif-ferences in retention reflect the effects ofdifferent encoding operations, although thepicture is complicated by the finding thatdifferent encoding operations are optimal

for different retrieval conditions (e.g., Eagle & Leiter, 1964; Jacoby, 1973).

Fourth, large differences in recall underdifferent encoding operations have beenobserved under conditions where the sub-jects' task does not entail organization orestablishment of interitem associations;thus the results seem to take us beyondassociative and organization processes asimportant determinants of learning andretention. It may be, of course, that theorienting tasks actually do lead to organiz-

ation as suggested by the results of Hydeand Jenkins (1973). Yet, it now becomespossible to entertain the hypothesis thatoptimal processing of individual words, qua

individual words, is sufficient to supportgood recall. Finally, the experiments mayyield some insights into the nature of learn-ing operations themselves. Classical verballearning theory has not been much con-cerned with processes and changes within

the system but has concentrated largely onmanipulations of the material or the experi-mental situation and the resulting effectson learning. Thus at the moment, we knowa lot about the effects of meaningfulness,word frequency, rate of presentation, var-ious learning instructions, and the like, butrather little about the nature and character-istics of underlying or accompanyingmental events. Experimental and theo-

retical analysis of the effects of variousencoding operations holds out the promisethat intentional learning can be reducedto, and understood in terms of, some com-bination of more basic operations.

The experiments reported in the presentpaper were carried out to gain further in-sights into the processes involved in goodmemory 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 memorytrace could usefully be regarded as the by-

product of perceptual processing; just asperception may be thought to be composedof a series of analyses, proceeding fromearly sensory processing to later semantic-associative operations, so the resultantmemory 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 furthersuggested that the durability of the memorytrace is a function of depth of processing.That is, stimuli which do not receive fullattention, and are analyzed only to a shal-low sensory level, give rise to very transientmemory traces. On the other hand, stimulithat are attended to, fully analyzed, andenriched by associations or images yield adeeper 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 theadvantage of focusing attention on the pro-cesses underlying trace formation and on

the importance of encoding operations;also, since memory traces are not seen asresiding in one of several stores, the depth

of processing approach eliminates the neces-sity to document the capacity of postulatedstores, to define the coding characteristic ofeach store, or to characterize the mechanismby which an item is transferred from onestore to another. Despite these advantages,there are several obvious shortcomings ofthe Craik and Lockhart viewpoint. Doesthe levels of processing framework say anymore than "meaningful events are wellremembered"? If not, it is simply a collec-tion of old ideas in a somewhat differentsetting. Further, the position may actuallyrepresent a backward step in the study ofhuman memory since the notions are muchvaguer than any of the mathematical modelsproposed, for example, in Norman's (1970)collection. If we already know that thememory trace can be precisely representedas

l = e- t(1- )

(Wickelgren, 1973), then such woolly

statements as "deeper processing yields a


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more durable trace" are surely far behind

us. Third, and most serious perhaps, thevery least the levels position requires issome independent index of depththere areobvious dangers of circularity present inthat 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 advantagesof 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 truestarting point, the concepts can he refined inthe light of experimental results suggestedby the theoretical framework. In thissense the levels of processing viewpoint willencourage rather different types ofquestion

a n d m a y y i e l d n e w i n s i g h t s . A f u r t h e r

point on the issue of general versusspecific theories is that while strengththeories o f memory are comme ndablyspecific and so-phisticated mathematically, the sophistica-tion may be out of place if the basic premisesare of limited generality or even wrong. Itis now established, for example, that thetrace of an event can he readily retrieved in

one environment of retrieval cues, while itis retrieved with difficulty in another (e.g.,Tulving & Thomson, 1973); it is hard toreconcile such a finding with the view thatthe probability of retrieval depends only onsome unidimensional strength.

With regard to an independent index ofprocessing depth, Craik and Lockhart

(1972) suggested that, when other thingsare 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., simplephrases or pictures) can be rapidly analyzedto a complex meaningful level. But withinone class of materials, or better, with onespecific stimulus, deeper processing isassumed to require more t ime. Thus, inthe present studies, the time to make deci-

sions at differen t levels of analysi s wastaken as an initial index of processing

depth.

The purpose of th is article is to describe

10 experiments carried out within the levelsof processing framework. The first experi-ments examined the plausibility of the basicnotions and attempted to rule out alterna-tive explanations of the results. Further

experiments were carried out in an attemptto achieve a better characterization of depthof processing and how it is that deepersemantic analysis yields superior memoryperformance. Finally, the implications of the

results for an understanding of learningoperations are examined, and the adequacyof the depth of processing metaphor ques-tioned.

EXPERIM ENTAL INVESTIGATIONS

Since one basic paradigm is used through-out the series of studies, the method will bedescribed in detail at this point. Variationsin the general method will be indicated aseach study is described.

General Method

Typically, subjects were tested individually.They were informed that the experiment con-cerned perception and speed of reaction. On eachtrial a different word (usually a common noun)was exposed in a tachistoscope for 200 msec.Before the word was exposed, the subject wasasked a quest ion about the word. The purposeof 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 necessitateprocessing either to a relatively shallow level(e.g., questions about t he word's physical appear-ance) or to a relatively deep level (e.g., questionsabout the word's meaning). In some experiments,the subject read the questions on a card; in others,the question was read to him. After reading orhearing the question, the subject looked in thetachistoscope with one hand resting on a ye s

response key and the other on a no response key.One second after a warning "ready" signal theword appeared and the subject recorded his (orher) decision by pressing the appropriate key(e.g., if the question was "Is the word an animalname?" and the word presented was TIGER, thesubject would respond yes). Af ter a ser i es of such question and answer trials, the subject wasunexpectedly given a retention test for the words.The expectation was that memory performancewould vary systematically with the depth ofprocessing.

Three types of quest ion were asked in theinitial encoding phase. (a) An analysis of thephysical structure of the word was effected byasking about the physical stru cture of the word


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TABLE 1

TYPICAL QUESTIONS AND RESPONSES USED INTHE EXPERIMENTS

(e.g. , Is the word printed in capital letters?").(b) A phonemic level of analysis was induced byasking about the word's rhyming characteristics(e.g., "Does the word rhyme with TRAIN?").(c) A semantic analysis was activated by askingeither categorical questions (e.g., "Is the word

a n a nima l na me ?" ) or " se nte nce " q ue st io ns ( e. g.,"Would the word fit the following sentence:' Th e g ir l p la ce d t he ____________ o n the t able'?").F ur th er e xa mp le s a re s ho wn i n T ab le 1 . A t e ac ho f the thr ee levels of a naly sis , ha lf of th e que s-tions yielded yes responses and halfno responses.

The general procedure thus consisted of explaining the perceptual-reaction time task to a singlesubject, giving him a long series of trialsin which both the type of question and yes-no decisions were randomized, and finally giving him anunexpected retention test. This test was either free recal l ("Rec all all the words y ou have s eenin th e p er ce ptu al tas k, in a ny or de r" ) ; c ue d r eca ll,in which some aspect of each word event was represente d as a cue ; or recogn ition, where copiesof the original words were re-presented along with a number of distractors. In the initial en-coding ph ase, res ponse late ncies wer e in fa ct recorded: A millisecond stop clock was started bythe timing mechanism which activated the tachisto -scope, and the clock was stopped by the subject'skey 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 responsecombinations (CAPITALS?-yes; SEN-TENCE?- no , and so on). The general prediction

wa s th at de ep er le ve l q ue stio ns wo uld ta ke lo nge r to answer but would yield a more elaborate mem-ory trace which in turn would support higher recognition and recall performance.

Experiment 1

Method. I n the firs t exper iment, single subjectswere given the perceptual-reaction time test; thisencoding phase was followed by a recognition tes t.Five types of question were used. First, "Is therea 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 fitin the sentence ? " Wh en th e fir st ty peof question was asked ("Is there a word pres-ent?"), on half of the trials a word was present


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a nd o n h alf of th e tr ials no w or d wa s pr ese nt o nthe tachistoscope card; thus, the subject could respond ye s when he detected any wordlike pat-tern on the card. (This task may be rather di f ferent f rom the others and was not used in furtherexperiments; also, of course, it yields difficulties of analysis since no word is presented on the negativet rials, these trials cannot beincluded in the measurement of retention.)

The stimuli used were common two-syllable nouns of 5, 6, or 7 let ters. For ty t rials were given; 4words represented each of the 10 conditions (5 levels yes-no). The sa me pool of 40 words was used forall 20 subjects, but each word was rotated through the 10 conditions so that, for different subjects, a wordwas presented as a rhyme-ye s stimulus, a category-no st imulus and so on. This procedure yielded 10

combinationsof questions and words; 2 subjects received each combinat ion. On ea ch trial, the q uestion was rea d toth e subjec t who was a l ready lo ok ingin the tachistoscope. After 2 sec, the word was exposed and the subject responded by saying ye sor nohis vocal response activated a voice key which stopped a millisecond timer. The experimenterrecorded the response latency, changed the word in the tachistoscope, and read the next question; trialsthus occurred approximatelyevery 10 sec.

After a brief rest, the subject was given a sheet with the 40 original words plus 40 similar dis-t ractors typed on i t . Any one subject had actual ly only seen 36 words as no word was presentedon negative "Word present?" trials. He was asked to check all words he had seen on the tach isto sco pe. Not ime l imit was imposed for this task. Two dif ferent randomizat ions of the80 recognition words were typed; one randomization was given to each member of the pair of subjects whoreceived identical study lists. Thus each subject received a unique presentation-recognition combination. The 20 subjects were college students of both sexes paid for theirservices.

Results and discussion. The results are

shown in Table 2. The upper portion

shows response latencies for the differentquestions. Only correc t answers were in-


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cluded in the analysis. The median latency

was calculated for each subject; Table 2shows mean medians. Although the fivequestion levels were selected intuitively, thetable shows that in fact response latencyrises systematically as the questions neces-

sitated deeper processing. Apart from thesentence level, yes and no responses tookequivalent times. The median latencyscores were subjected to an analysis ofvariance (after log transformation). The

analysis showed a significant effect of level,F (4, 171) = 35.4, p < .001, but no effectof response type (yes-no) and no inter-action. Thus, intuitively deeper questionssemantic as opposed to structural deci-sions about the wordrequired slightlylonger processing times (150-200 msec).

Table 2 also shows the recognition re-sults. Performance (the hit rate) increasedsubstantially from below 20% recognized

for questions concerning structural charac-

teristics, to 96% correct for sentenceyesdecisions. The other prominent feature ofthe recognition results is that the yes re-sponses to words in the initial perceptualphase were accompanied by higher sub-sequent recognition than the no responses.Further, the superiority of recognition ofyes words increased with depth (until thetrend was apparently halted by a ceiling

effect). These observations were confirmedby analysis of variance on recognition pro-portions (after arc sine transformation).Since the first level (word present?) hadonly yes responses, words from this levelwere not included in the analysis. Type ofquestion was a significant factor, F (3, 133)= 52.8, p < .001, as was response type (yesno), F (1, 133) = 40.2, p < .001. TheQuestion Response Type interaction was

also significant, F (1, 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 RECOGNITIONPERFORMANCEFOR WORDSAS A FUNCTIONOF

INITIAL TASK (EXPERIMENT 1)

ing questions were, associated with markeddifferences in recognition performance:Semantic questions were followed by higherrecognition of the word. In fact, Table 2shows that initial response latency is sys-tematically related to subsequent recogni-tion. Thus, within the limits of the present

assumptions, it may be concluded thatdeeper processing yields superior retention.It is of course possible to argue that the

higher recognition levels are more simplyattributable to longer study times. Thispoint will be dealt with later in the paper,but for the present it may be noted that inthese terms, 200 msec of extra study timeled to a 400% improvement in retention.It seems more reasonable to attribute theenhanced performance to qualitative differ-ences in processing and to conclude thatmanipulation of levels of processing at thetime of input is an extremely powerfuldeterminant of retention of word events.The reason for the superior recognition ofyes responses is not immediately apparent

it cannot be greater depth of processing inth e simple sense, since yes and no responsestook the same time for each encoding ques-tion. Further discussion of this point isdeferred until more experiments are described.

Experiment 2 is basically a replication ofExperiment 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-


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FIGURE 1. Initial decision latency and recognition performance for words as afunction of the initial task (Experiment 2).

script (uppercase or lowercase), rhyme questions, andsentence questions ( i n which subjects weregiven a sentence frame with one word missing).During the initial perceptual phase 60 questionswere presented: 10 ye s and 10 no questions ateach of the three levels. Question type was ran-domized within the block of 60 trials. The ques-t ion was presented audi tori ly to the subject ; 2sec later the word appeared in the tachistoscopefor 200 msec. The subject responded as rapidlyas possible by pressing one of two response keys.After completing the 60 initial trials, the subjectwas given a typed list of 180 words comprisingthe 60 original words plus 120 dist ractors. Hewas told to check al l words he had seen in thefirst phase.

All words used were five-letter common con-crete nouns. From the pool of 60 words, twoquestion formats were constructed by randomlyallocating each word to a question type until all

10 words for each question type were filled. Inaddition, two orders of question presentation andtwo random orderings of the 180-word recogni-t ion l i s t were used. Three subjects were testedon each of the eight combinations thus generated.The 24 subjects were students of both sexes paidfor their services and tested individually.

Results and discussion. The left-handpanel of Figure 1 shows that responselatency rose systematically for both responsetypes, from case questions to rhyme ques-tions to sentence questions. These dataagain are interpreted as showing that deeperprocessing took longer to accomplish. At

each level, positive and negative responsestook the same time. An analysis of varianceon mean medians yielded an effect of ques-tion type, F (2, 46) = 46.5, p < .001, butyielded no effect of response type and nointeraction.

Figure 1 also shows the recognitionresults. For yes words, performance in-creased from 15% for case decisions to 81%for sentence decisionsmore than a five-fold increase in hit rate for memory per-

formance for the same subjects in the sameexperiment. Recognition of no words alsoincreased, 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 rhymes > case); retention is again

superior for words given an initial yesresponse and recall of twice-presented wordsis higher than once-presented words. Ananalysis of variance confirmed these obser-vations. Semantic questions yielded higherrecall, F (2, 38) = 36.9, p < .01; more yes

responses than no responses were recalled,F ( 1 , 19) = 21.4, p < .01; two presenta-tions increased performance, F (1, 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 Number of Presen-tations interaction, F (2, 38) = 10.8, p

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