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Imagery and long-term retention
JOURNAL OF VERBALLEARNINGAND VERBALBEHAVIOR12, 689-700 (1973)
Imagery and Long-Term Retention1 IAN BEGG AND RICHARD ROBERTSON
McMaster University Long-term retention of high- and low-imagery nouns was assessed in incremental free recall, paired-associates learning, and cued and noncued recall of noun pairs. I n each case imagery had a clear positive effect on long-term retention, and the effect could not be explained by differential acquisition of the material. Results of the experiments were also examined by analyzing subjective organization, and by comparing cued and noncued recall. Such results were interpreted as supporting an imagery-organization hypothesis which asserts that images aroused by discrete verbal items can be combined into complex, integrated images, the components of which provide effective cues for retrieving or redintegrating the remainder of the unit.
The main purpose of this paper is to determine whether the familiar facilitatory effects of mental imagery on the acquisition of verbal material persist over a relatively long time interval. There is a dearth of experimental evidence germane to the question, and what little evidence there is is conflicting. Both Butter (1970) and Postman (1972) reported that the positive effect of imagery on learning became negative after a 1-wk retention interval, while Palermo (1970) and Yuille (1971) found that imagery effects were positive but considerably reduced in long-term tests of retention. Since existing imagery theories (e.g., Paivio, 1971) would be seriously compromised by a failure to find long-term effects of imagery, and since such failure would negate any potential practical implications of imagery in learning, it is of some importance to resolve the issue. Consequently three experiments were conducted to examine long-term free recall of nouns, long-term retention of paired-associates, and long-term
cued and noncued recall of noun pairs. In each case, nouns differing in image-arousing capacity were used as stimulus material. A second purpose of the paper is to present evidence related to the organizational properties of images in acquisition and retention. Begg (1972) suggested that imagery is an effective variable in recall largely because images can be readily combined into integrated subjective units. Each verbal item represented in such a unit is an effective cue for retrieving or redintegrating the remainder of the unit. In the first experiment in this paper, subjective organization was measured to determine whether imagery and long-term recall are related to such organization, and in the third experiment, cued and noncued recall were contrasted to determine whether imagery effects would be most pronounced in cued recall, both during acquisition and after a 6- to 10-day interval.
EXPERIMENT I z The research was funded by National Research Imagery has a clear facilitatory effect on Council of Canada Grant A8122 to the first author. The second experiment was conducted as an Indepenthe acquisition of nouns, whether defined by dent Study by Charles and Marian Winegard. The instructions to image (e.g., Gupton & Frincke, third experiment constitutes part of a Master's Thesis 1970; Kirkpatrick, 1894) or by ratings of by the second author. Reprints may be obtained from image-arousing capacity, concreteness, or Ian Begg, Department of Psychology, McMaster vividness (e.g., Dukes & Bastian, 1966; University, Hamilton, Ontario, Canada, L8S 4K1. Copyright © 1973by AcademicPress, Inc. 689 All rights of reproduction in any form reserved. Printed in Great Britain
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Paivio, 1968; Tulving, McNulty & Ozier, recall, particularly as related to imagery. 1965; Winnick & Kressel, 1965). Consequently That is, in the acquisition task, neither the it is difficult to equate learning of material recall data nor the organization data should differing in image-arousing capacity, in order contain main effects of imagery level, while in to conduct an unbiased test of the hypothesis the retention task, both dependent variables that imagery facilitates retention. Groninger should be positively related to imagery level. (1971) equated acquisition of lists of 25 highIn brief, two hypotheses were tested in the imagery nouns learned either by rote instruc- first experiment. First, more concrete than tions or imagery-mnemonic instructions by abstract nouns should be recalled on both the requiring a perfect recitation of each list. The 48- and 72-hr retention tests. Second, concriterion was reached more quickly by the crete nouns recalled contiguously on the imagery group than the control (14 versus 17 retention test should be more likely than min). After 1 and 5 wk, subjects again recalled abstract nouns recalled contiguously to have the lists. The imagery group enjoyed a 14~o been recalled in adjacent positions during the advantage at 1 wk, and a 19 ~o advantage after final acquisition trial. 5 wk, assessed by the total number of words recalled. In the present experiment, imagery Method was defined by using high- and low-imagery Subjects. Ten student volunteers from nouns as stimulus material, and an attempt McMaster University were each paid $5.00 was made to equate learning using a paradigm for their participation. Five subjects served described below. in each of two presentation orders. The procedure used in Experiment I was a Materials. Twenty-five concrete nouns (I > modified version of an incremental task repor- 6.00) and 25 abstract nouns (I < 3.60) were ted by Mandler and Dean (1969). On the first chosen from the Paivio, Yuille, and Madigan trial, the subject was presented with one word, (1968) norms. All nouns had frequencies of which he then recalled. On the second trial, A or AA. From the concrete words, one was the first word and a new word were presented randomly chosen as List 1. A second concrete and recalled. On each subsequent trial one word was chosen and added to List 1, which new word was added to the list, in a new ran- was subsequently reordered randomly, and dom order each time, and recall was requested, called List 2. Similarly, a third word was until on Trial 25, the subject attempted to chosen, and List 3 was constructed. The recall 25 words. procedure was followed until there were 25 The task was chosen for two reasons. First, lists of concrete nouns, ranging in length from there is no reason to expect differential one to 25 items. Twenty-five lists of abstract acquisition as a function of concreteness, nouns were also constructed using the same since performance is typically very good in the procedure. task and at least some items are overlearned. Procedure. The experiment was conducted Second, subjective organization can be mea- in three sessions for each subject. The first sured between successive written recall proto- two sessions were 24 hr apart, and the last cols to determine whether imagery is related two, 48. Half the subjects heard concrete to organization, and whether organization is lists during the first session and abstract during related to long-term retention. If, as Begg the second, while the reverse was true for the (1972) suggested, imagery is an effective remaining subjects. Each list was read to the variable in recall largely because images can subject at the rate of 4 sec per item, with an be readily combined into integrated subjective equal amount of time allotted for recall. Thus units, analyses of output-output organization a subject first heard one word, recalled it, then should provide results parallel to analyses of heard two words, recalled them, and so on
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until the 25 lists had been presented and •where n is the number of words in common in recalled. Each of the first two sessions re- the two lists. The measure was calculated quired about 1 hr. In the final session, the starting with Trials 5 and 6, since the first subject was simply asked to recall as many trials have excessively high chance levels. The words from the first two sessions as he could in scores were averaged into four blocks of five 5 min. The subjects were given standard free trials each, and analyzed by a 2 x 2 × 4 recall instructions at the start of each session, analysis of variance with order, concreteness, and were not instructed that long-term recall and blocks as the factors. Concreteness interacted with order, F(1, 8 ) = 22.1, p < .01, would be required. since, as with the recall data, second-day Results and Discussion performance exceeded first-day performance Acquisition: Proportion correct. For each regardless of concreteness. For concrete subject, the proportions correct on the 25 nouns, the first and second day scores were trials were averaged over blocks of five trials .39 and .71, while for abstract they were .50 to obtain five scores within each level of and .59. By post hoc t tests, concrete nouns concreteness. These data were analyzed by a acquired on the second day were more organ2 × 2 x 5 analysis of variance, with order ized than those acquired on the first day (concrete on the first day, or abstract on the (p < .05), although neither differed reliably first day) as the independent factor, and con- from the amount of organization in the creteness (concrete or abstract) and blocks as abstract nouns. Thus the pattern of results repeated factors. The only significant main from the analysis of the organization data is effect was blocks, F(4, 32)=4.16, p <.01, similar to the results from the analysis of with respective means of 1.00, .95, .90, .93 and recall data. .94. Concreteness and order interacted, F(1, 8) Retention: Proportion correct. The pro= 9.37, p < .01, since second-day performance portions of words correctly recalled on the exceeded first-day performance regardless of retention testwere analyzed by a 2 x 2 analysis concreteness. For concrete words, the pro- of variance with order of presentation as an portions were .92 and .98, while for abstract, independent factor, and concreteness as a they were .92 and .95. The task thus yields repeated factor. Recall of concrete words performance data in which recall of concrete exceeded recall of abstract words, .72 versus and abstract words is equal on the first day, .54, F(1, 8)=17.3, p < . 0 1 . Concreteness and not very different on the second. As a interacted with order, F(I, 8) = 45.6, p < .01, further check on the equivalence of learning as shown in the left-hand panel of Figure 1. 2 o f the concrete and abstract nouns, perfor- A number of important points can be made mance in the final block of five trials was from the figure. First, the interaction clearly inspected separately. For the concrete and represents the fact that recall after 72 hr (the abstract nouns learned on the first day, bottom two points in the figure) was lower than performance was at .87 and .93, respectively, recall after 48 hr. Note also that the facilitawhile both were recalled at .99 on the second. tive effect of imagery does not diminish over Consequently, any retention differences as a the interval: at 48 hr, concrete nouns enjoyed function of imagery cannot be attributed to an advantage of .18 (.87-.69), and at 72 hr differential acquisition levels. the advantage was also .18 (.58-.40). By post
Acquisition:
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organization.
Organization was measured by Mandler and Dean's (1969) ITR(2), defined as the number of bidirectionally co-occurring pairs in two successive output protocols, divided by n-l,
The figures are plotted by retention interval rather than by order, although the results were analyzed by order. The subjects represented by the top-left and bottom-right points received concrete items on the first day.
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Fro. 1. Recall and organization of concrete and abstract nouns after a 48- or 72-hr delay.
hoc t tests, the imagery effect was reliable at both delays, and 72-hr recall was worse than 48-hr recall within both levels of concreteness (ps < .05). Retention: Output-output organization. The ITR (2) measure was computed between the last recall trial during acquisition and the longterm recall protocol. The results were analyzed by a 2 × 2 analysis of variance, with factors as above. Concrete lists were more organized than abstract, .52 versus .27, F(1, 8) =25.7, p < . 0 1 . Concreteness and order interacted, F(1, 8 ) = 50.2, p < .01, as shown in the right-hand panel of Figure 1. The interaction resembles the interaction in recall data at the longer term, just at it did during acquisition. Post h o c t tests revealed that 72-hr recall was less organized than 48-hr recall at both levels of concreteness, and that concreteness was positively related to organization at both delay intervals (ps < .05). The data support two strong conclusions.
First, concreteness is a powerful variable in retention of nouns, even in a situation where no facilitation is afforded concrete nouns in acquisition. Taking Groninger's (1971) results into account, it is clear that mental imagery facilitates long-term retention of words, and the effect does not diminish over the time intervals used in these experiments. Second, concreteness and organization are highly related, both during the acquisition and long-term retention of words. Although the present data do not justify inferences of causality between the two variables, the relation can be predicted from an imagery-organization hypothesis outlined by Begg (1972, 1973), who argued that images aroused by concrete words could be organized into complex images in memory, and that retrieval of part of the compound image would provide subjective cues for retrieving or redintegrating the rest of the image, with contingent enhancement of recall. If the hypothesized subjective organiza-
IMAGERY AND LONG-TERM RETENTION
tion and redintegration occur, high intertrial output organization should be apparent, as in the present experiment. EXPERIMENT I [
The second experiment investigated the fate of imagery effects in paired-associates learning, with a 72-hr delay between the last acquisition trial and the retention test. The effect of imagery in paired-associates learning is well documented (see Paivio, 1969, 1971), with the greatest facilitation due to imagery in the cue members of the pairs (stimuli), although imagery level also affects recall of the to-be-remembered items (responses). The question of interest is whether the imaginal facilitation of paired-associates learning persists over longer periods of time. Butter (1970) reported an experiment in which, among other things, subjects read noun-digit pairs which they subsequently recalled after 2 min, 20 rain, or 2 days. She found that although word concreteness was positively related to digit recall after 2 min, the effect was virtually absent after 20 min, and was strongly reversed after 2 days. Over the range of the experiment, the recall of digits associated with concrete nouns declined to about a third of the short-term level, while surprisingly, the recall of digits associated with abstract words doubled between 2 min and 2 days. However, Yuille (1971) repeated the experiment and failed to replicate the concreteness reversal. In his experiment the concreteness effect was strong after 2 min, and was still positive, although nonsignificant after 2 days. Yuille (1971) also reported data from two other experiments in which subjects learned paired-associate lists containing the four combinations of concrete (C) and abstract (A) stimulus and response terms. In both experiments and at both 0- and 1-wk delays, the order of conditions with respect to the number correct was CC, CA, AC, and AA, the usual order. Adding over the two experiments, it is
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possible to estimate the size of the effect of imagery both on the stimulus side (CC + CA AC - AA) and the response side (CC + AC - C A - AA). The stimulus effect at shortterm (14.2) was slightly larger than the response effect (12.6). At the longer delay, the stimulus effect (7.5) was still greater than the response effect (3.5), although both were reduced considerably, being 53 ~ and 28 of their respective former values. Similarly, Palermo (1970) reported that the stimulus imagery effect was 50 ~ of its former value after a 2-day delay, while Schnorr and Atkinson (1969) found the facilitation due to imagery instructions still present after a week, but at a reduced level. The method of estimating the size of the concreteness effect used above is open to criticism. Since memory decay is typically of some geometric or exponential form (e.g., Wickelgren, 1970), conditions starting at relatively higher performance levels would decline over time relatively faster than conditions starting at lower levels, if the amount of decline is expressed in absolute terms. However, if the decline is expressed proportionally, this may not be the case. For Yuille's (1971) data, each of the remaining three conditions can be expressed as a proportion of performance in the CC condition, both in the immediate and delayed tests. When the imagery effects are calculated as above, but using proportions, the short-term stimulus and response imagery effects are .51 and .45, respectively, compared with their respective long-term values of .77 and .35. Thus the stimulus imagery effect at the longer delay is 151 ~o of its short-term value, and the response imagery effect is 78 ~o of its former value. Schnorr and Atkinson's long-term effect is 40~o with the arithmetic calculation while with ratios it is 76 ~ of the short-term effect. Therefore, it can be concluded that the diminution of the imagery effect over time is largely a function of the way in which the effect is measured. Perhaps the least controversial assessment o f the size of the effect -
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would be to convert scores at both the shortand long-term to z scores. However, a better way of examining the effects would be to use tasks in which concrete and abstract items do not differ in acquisition, so that differences in long-term recall can be assessed directly. Postman (1972) reported an experiment in which CC, CA, AC, and AA noun pairs were learned to the criterion of 12 of 16 pairs correct. The respective pairs required 4, 6, 9, and 13 trials to reach criterion. After 1 wk, memory for the pairs was again assessed. In terms of losses from projected scores, the order of conditions on the first long-term test trial was AC, CA, AA, and CC, although by the second test trial the middle two conditions had reversed. Since the ordering of conditions is highly discrepant from any predicted order based on theoretical accounts of imagery, it is important to determine whether the reversal of the imagery effect is due to some aspect of the experiment or due to imagery per se. It is unlikely that the reversal could result from differential accessibility of the individual words, since imagery is positively related to long-term retention of words (Experiment I; Groninger, 1971). The clue to understanding the reversal more likely lies in the associative phase of the task; that is, perhaps imagerymediated associations are more vulnerable to interference or decay than other associations over the time period of interest. However, before explaining the reversal, it is desirable to see whether the effect can be replicated. In the second experiment, subjects learned paired-associates consisting of either CC or AA pairs. The pairs were presented in either 16- or 50-item lists, and were learned to a criterion of 50 70 correct, 75 ~ (76 70 for the 50-item list) correct, or 100 K correct. Procedural differences between the present experiment and Postman's experiment require explication. First, short and long lists were used since in Postman's 16-item list the difference in number of trials to criterion between the CC and AA lists (4 versus 13) was proportionately very large. Second, three
different criterion levels were used simply for their parametric value. The third major difference is that as a subject correctly anticipated a response, that pair was dropped from the list. Thus the present experiment controlled the number of correct recalls for CC and AA pairs, while Postman's experiment controlled the proportion of the list recalled. A problem with the latter procecure is that despite the equality of criterion performance, there can be a wide disparity in the number of times a given pair is correctly recalled. To illustrate with Postman's data, if we assume the number of items recalled on a given trial is a linear function of the number of presentations, then 30 CC items were correctly recalled over the four trials required to reach the criterion of 12 items correct, and 84 AA items were correctly recalled. Since it is not unreasonable to expect that long-term recall is positively related to the number of shortterm recalls, Postman's results could reflect this contaminating variable rather than concreteness. Thus, for the present purposes, it was deemed desirable to equate the number of correct anticipations rather than to equate list performance. Method Subjects. Sixty students from McMaster University were paid $2 per hour for their participation in the experiment. Five subjects served in each of 12 groups. Materials. One hundred concrete (I ~>6.00) and 100 abstract (I ~<3.90) nouns were selected from the Paivio et al. (1968) norms. Frequency levels were roughly equated, with all frequencies greater than 15, and most A or AA. The 100 concrete nouns were randomly assigned to 50 pairs, as were the abstract. For the short lists, 16 concrete and 16 abstract pairs were selected from the 50, again with frequency controlled. Each pair was typed on an index card, with one word on each side. Procedure. The basic design was a 2 x 2 x 3 factorial, with independent groups. Thus there were concrete and abstract lists, short
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and long lists, and 50, 75, and 100 ~ criterion levels. In any given condition, a subject was presented with a deck of cards. On the first trial, the experimenter read aloud the nouns on the front and back of the cards, while the subject watched. The cards were then shuffled and given to the subject, who attempted to anticipate the noun on the back of the card, and then turned the card over. If the anticipation was correct, the card was removed from the deck. At the end of each run through the deck, the remaining cards were reshuffled and handed back to the subject. Acquisition stopped at the response which met the criterion. For the retention test, subjects were recalled after 72 hr, and were shown and read the noun on the front of each card. They attempted to anticipate the second member of the pair on one trial. All presentations in each phase of the experiment were self-paced, although subjects took about 5 sec per card. Results and Discussion The number of pairs correctly anticipated at the long term were analyzed separately for the short and long lists, in each case by a 2 × 3 analysis of variance, with concreteness and criterion level as independent factors. For the short list at the long delay, more concrete than abstract pairs were correctly anticipated, 6.00 versus 3.47, F(1, 24) = 9.53, p < . 0 1 . There was also a main effect of criterion level, F(2, 24) = 3.99, p < .05. Post hoc t tests were performed on the data, with the following conclusions. More concrete than abstract pairs were correctly anticipated in both the 75 and 100 K criterion groups (ps < .05), but not in the 50 ~ group. For the abstract pairs, there were no differences in long-term recall as a function of criterion group, while for concrete pairs, the 5 0 ~ group led to lower levels of performance than the other two conditions (ps < .05), which did not differ from each other. There is thus one conclusion. Concreteness is positively related to long-term retention when the number of correct anticipations is controlled
during acquisition, except when the original criterion is lenient (50 7oo). The results for the longer list were similar. More concrete than abstract pairs were correctly anticipated, 20.5 versus 11.5, F(1, 24) =23.0, p < .001, and long-term performance increased with stringency of criterion, F(2, 24) = 22.9, p < .001. The variables interacted, F(3, 2 4 ) = 6.28, p < .01, as shown in Figure 2. As in the short list, concrete pairs i~
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led to better recall than abstract at both the 75 and 100 ~ criterion levels (ps < .05) but not at the 50~o level. In concrete pairs, each increase in stringency of criterion led to an increase in recall (ps < .05), while in the abstract pairs, only the 100 ~ and 50 ~o criteria led to reliably different long-term performance. The results of the experiment are straightforward. Imagery facilitates retention over a 72-hr delay when recall is equated at acquisition, unless the equation is at a relatively low
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level. Concrete items benefit disproportionately from increased stringency during acquisition, despite the fact that concrete and abstract pairs were initially recalled equally often. Finally, the above-mentioned effects are stronger when the lists are longer. EXPERIMENTIII The purpose of the third experiment is to extend the results obtained in the first two experiments, as well as to test some predictions derived from a theoretical account of imagery facilitation. First, the question of central importance in this paper concerns long-term imagery effects, and as a result, the experiment investigated long-term memory for noun pairs, in a task designed to emphasize the pairness of the items. Second, both cued and noncued recall of the pairs were collected at acquisition and after a delay of 6-10 days. If imagery effects in long-term memory are qualitatively similar to effects in short-term memory, then effects found by Begg 0972, 1973) should be observable after the delay. That is, the facilitative effect of cueing should be more pronounced with concrete than abstract pairs at both acquisition and retention. Likewise, in noncued recall, a higher proportion of concrete than abstract nouns recalled should be in pairs, regardless of whether the recall is at short- or long-term. In the third experiment, then, subjects were presented with concrete and abstract noun pairs for five trials. On each trial, they were instructed to form either imaginal or verbal mediators for each pair. Latencies were recorded. After the fifth trial, subjects were tested for either cued or noncued recall of the pairs. The subjects were again tested after 6-10 days. Method Subjects. Thirty-two student volunteers from McMaster University were paid $2 per hour for their participation, with eight subjects in each factorial combination of set
(imagery or verbal) and cueing (present or absent). Materials, Sixty high-imagery (•>6.00) and 60 low-imagery ( I < 3.90) nouns were selected from the Paivio et al. (1968) norms, with frequency values of A or AA for all but four nouns of either set. Thirty high-imagery and 30 low-imagery pairs were selected randomly. Each pair was typed in upper case on an index card. Procedure. The cards were presented tachistoscopically, to the right of a fixation point. The subjects initiated each exposure by pressing a button, which also started a timer, and terminated the trial by releasing the button upon completion of the processing required by the instructions. Half the subjects were given imagery mediation instructions, and half were given verbal. After releasing the button, subjects described their mediators. Each subject received the 60 pairs in a different random order in each of five trials. They were instructed to try to use the same mediator on each trial, but to generate a new one if they could not recall the old one. After the fifth trial, subjects within each group were randomly assigned either to a cued or noncued recall condition. For cued recall, response sheets were provided on which one member of each pair was typed, and the subject was asked to fill in the missing words. Right- and left-hand members served as cues equally often. For noncued recall, the subject was asked to write down as many words or pairs as he could. After a delay of 6 days, subjects were mailed or given response sheets identical to those filled out in immediate recall and were requested to fill them out again. If replies were not returned within 3 days, subjects were contacted by telephone. All subjects replied between 6 and 10 days of the previous test. Results and Discussion Mediation lateneies. Mean latencies were calculated for each subject on each trial, for both concrete and abstract pairs. Because of
IMAGERYAND LONG-TERMRETENTION large discrepancies in the variances, each trial was separately analyzed by a 2 × 2 analysis of variance, with set (imagery or verbal) as an independent factor, and concreteness as a repeated factor. All F ratios had df= 1, 30. On the first trial, verbal instructions led to shorter latencies than imagery instructions, 6.12 versus 10.4 sec, F = 4.20, p < .05, but the effect was not reliable on any later trial. The interaction between the variables was not reliable on any trial. The concreteness effect, however, was highly reliable on every trial, p < .001, with respective Fs of 21.0, 38.0, 42.9, 60.8, and 74.4, with concrete pairs associated with shorter latencies than abstract pairs. Word recall. As a preliminary analysis, the numbers of words correctly recalled in each of the four combinations of cueing (present or absent) and time (short term or long term) were analyzed by a 2 x 2 x 2 analysis of variance, with set (imagery or verbal) as the independent factor, and concreteness (concrete or abstract) and term (stimulus or response) as repeated factors. More concrete than abstract words were recalled (p < .01) in each of the four analyses. More stimulus than response terms were recalled in the cued longterm condition (p < .01), while recall in the other three conditions was symmetrical. No interactions nor effects of set were significant in any of the analyses. Because of the results of the preliminary analysis, the major analysis of word recall was a 2 x 2 x 2 analysis of variance, with cueing (present or absent) as the independent factor, and concreteness (concrete or abstract) and time (short-term or long-term) as repeated factors. The proportion of items correct was the dependent measure, since there were potentially twice as many correct items in the noncued conditions as in the cued conditions. All three main effects were reliable (df= 1, 30; ps < .001), with cued recall exceeding noncued recall, .69 versus .49, F = 2 1 . 7 , recall of concrete items exceeding abstract, .71 versus .45, F = 60.1, and short-term recall exceeding
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long-term recall, .70 versus .46, F = 6 4 . 0 . The effects of cueing and concreteness were not independent, since the two variables interacted, F = 4.29, p < .05. The interaction reflects the fact that the facilitative effect of concreteness was greater in cued than noncued recall, or alternatively, the effect of cueing was greater with concrete than abstract pairs, resulting in disproportionately high cued recall of concrete nouns. Concreteness also interacted with time, F = 86.5, p < .001. The concreteness effect was larger at the long-term than the short-term, since more abstract than concrete items were forgotten over the interval between tests. All the above effects were slightly qualified by the three-way interaction, F = 30.1, p < .001, shown in Figure 3. The facilitative effect of cueing was very small in the long-term recall of abstract pairs, but present in the other three comparisons. The
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effects of time and concreteness are minimally qualified by the interaction. Additionally, the two-way interaction of concreteness with cueing, although present in absolute terms in both long- and short-term performance, was more pronounced at the longterm. Finally, the Concreteness x Time interaction was more pronounced in cued than noncued recall. With respect to word recall, then, the facilitative effect of imagery increases over time, and is greater in cued than noncued recall at each level of time. The first finding is completely in line with the results from the first two experiments, and the second is consistent with the results reported by Begg (1972, 1973). Pair recall. The number of pairs correctly recalled in noncued recall was analyzed by a 2 x 2 x 2 analysis of variance, with set (imagery or verbal) as the independent factor, and concreteness (concrete or abstract) and time (short- or long-term) as repeated factors. More concrete than abstract pairs were recalled, .56 versus .35, F(1, 14)=17.8, p < .001, and short-term retention was superior to long-term, .55 versus .35, F = 22.5, p < .001. The two variables did not interact, but, if anything, the concreteness effect was larger at the long term (.45 versus .24) than at the short term (.65 versus .47). Once again, there is no hint of a diminution of the effectiveness of imagery over time. Conditionatprobabilities. For each subject, two ratios were calculated: The number of stimulus terms recalled was divided into the number of pairs recalled, and the number of response terms recalled was divided into the number of pairs recalled. The proportion of words recalled that were in pairs (the mean of the two ratios) was analyzed by a 2 × 2 × 2 analysis of variance, with the same factors as above. The conditionals associated with concrete phrases were higher than those with abstract, .947 versus .805, F(1, 14)= 8.00, p < .025, and the concrete conditionals diminished less over time than did the abstract, F = 4.81, p < .05. The respective short- and
long-term values for concrete pairs were .969 and .925, while for abstract they were. 853 and .756, Conditional probabilities, calculated as above, are also higher for meaningful concrete than abstract phrases (Begg, 1972), and for concrete noun pairs learned under interactive rather than separated imagery instructions (Begg, 1973). As a generalization, it seems that tasks or items designed to emphasize pairness are characterized by higher conditional probabilities than those that are not, although the relation is not statistically necessary. Long-term recall conditionalized on shortterm recall. Since initial recall levels were higher for concrete than abstract pairs, longterm recall was examined for pairs at given levels of short-term recall. In cued recall, 76 ~o of the concrete pairs correct at short-term were also recalled at long-term, while for abstract, only 40 ~o of such items were recalled at long-term (p < .001). In noncued recall, several short-term levels of performance were isolated, and long-term recall examined. First, pairs correctly recalled at short-term were considered. Of words in such pairs, 60 ~ of concrete and 45 ~ of abstract (p < .001) were also recalled at long-term. Second, for pairs in which only one item was recalled at shortterm, 5 2 ~ of concrete and 1 4 ~ of abstract words (p < .001) were recalled at long-term. Finally, for unrecalled pairs at short-term, 30 Yo of concrete and 18 ~ of abstract words were recalled at long-term (p < .02). Thus the differential levels of recall in the long-term condition cannot be attributed to differential recall of concrete and abstract words at the time of acquisition. GENERAL DISCUSSION Because of the quantity of data presented, a summary is in order. First, considering longterm recall, it is safe to conclude that imagery facilitates retention. In Experiment I, more concrete than abstract nouns were recalled after 48 and 74 hr, despite the fact that
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acquisition did not favor the concrete nouns. In Experiment II, more concrete than abstract responses were correctly anticipated after 72 hr when acquisition was controlled at 75 or 100 ~o correct anticipations. In Experiment III, several results support the conclusion. In both cued and noncued recall, more concrete than abstract words were recalled after a week, and the effect could not be attributed to differential acquisition, since the long-term imagery effect was larger than the short-term effect, and was strong even in concrete and abstract pairs that were equally well recalled at the short term. Further, more concrete than abstract pairs were recalled in long-term noncued recall, and again the effect was larger at long than short term. Finally, concrete words recalled in long-term noncued recall were more likely to be in pairs than were the abstract words, and the difference was larger after a week than at the time of acquisition. Because of the difficulty of controlling acquisition levels of concrete and abstract materials, each of the three experiments is open to criticism for failure to equate learning on some basis. However, the overall conclusion based on the very different techniques employed is unshakeable: Imagery facilitates retention as well as acquisition. A second class of conclusions is of more theoretical importance, and concerns integration as a concept. Begg (1972, 1973) argued that the usual imagery effect is largely a function of the fact that images aroused by discrete verbal items can be combined into complex images which operate as units in memory, being remembered or forgotten as units, and with each component of the image serving as an effective cue for redintegrating the rest of the unit. In the first experiment, the facilitative effects of imagery in retention were closely paralleled by changes in the amount of subjective organization used by subjects. In the third experiment, imagery effects were more pronounced in cued than in noncued recall, and even in noncued recall members of concrete pairs were more likely to share a
c o m m o n fate in memory than were members of abstract pairs. Consequently, the integration hypothesis is supported as an explanation ofimaginal facilitation of acquisition, and is extended as an explanation of imagery effects in longer-term retention. Thus we conclude that imagery facilitates retention, and we suggest that the integrative properties of images are responsible for the effect. REFERENCES
BraG, I. Recall of meaningful phrases. Journal of Verbal Learning and Verbal Behavior, •972, 11, 431-439. BEOG,I. Imagery and integration in the recall of words. CanadianJournalof Psychology, 1973,27,159-167. BUTTER,M. J. Differential recall of paired associates as a function of arousal and concreteness-imagery levels. Journal of Experimental Psychology, 1970, 84, 252-256. DUKES, W. F., & BASTIAN,J. Recall of abstract and concrete words equated in meaningfulness. Journal of Verbal Learning and Verbal Behavior, •966, 5, 455-458. GRON~NOER,L. D. Mnemonic imagery and forgetting. Psychonomic Science, 1971, 23, 161-163. GtrPTON, T., & FRINCKE, G. Imagery, mediational instructions, and noun position in free recall of noun-verb pairs. Journal of Experimental Psychology, •970, 86, 461-462. KIRKPATRICK,E. An experimental study of memory. Psychological Review, 1894, 1,602-609. MANDLER, G., & DEAN, P. J. Seriation: Development of serial order in free recall. Journal of ExperimentalPsychology, •969, 81,207-215. PAIVIO,A. A factor-analytic study of word attributes and verbal learning. Journal of Verbal Learning and VerbalBehavior, •968, 7, 41-49. PAWIO,A. Mental imagery in associative learning and memory. PsychologicalReview, 1969, 76, 241-263. PAIVIO,A. Imagery and verbalprocesses. New York: Holt, Rinehart & Winston, 1971. PAWIO, A., YU~LLE,J. C., & MADMAN, S. A. Concreteness, imagery, and meaningfulness values for 925 nouns. Journalof ExperimentalPsychology, Monograph Supplement, 1968, 76 (1, Pt. 2). PALERMO,D. S. Imagery in children's learning: Discussion. PsychologicalBulletin, 1970, 73, 415-421. POSTMAN, L. The experimental analysis of coding processes. Paper presented at the Midwestem Psychological Association Meetings. Cleveland, 1972.
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SCHNORR,J. A., & ATK1NSON,R. C. Repetition versus imagery instructions in the short- and long-term retention of paired-associates. Psychonomic Science, 1969, 15, 183-184. TULVING,E., McNULTY,J. A., & OZIER,M. Vividness of words and learning to learn in free-recall learning. Canadian Journal of Psychology, 1965, 19, 242-252. WICK~LGREN, W. A. Multitrace strength theory. In Norman, D. A. (Ed.) Models of human memory. New York: Academic Press, 1970.
WINNICK, W. A., t~ KRESSEL, K. Tachistoscopic recognition thresholds, paired-associate learning, and immediate recall as a functionof abstractnessconcreteness and word frequency. Journal of Experimental Psychology, 1965, 70, 163-168. YUILLE,J. C. Does the concreteness effect reverse with delay2 Journal of Experimental Psychology, 1971, 88, 147-148.
(Received June 8, 1973)
Imagery and Long-Term Retention1 IAN BEGG AND RICHARD ROBERTSON
McMaster University Long-term retention of high- and low-imagery nouns was assessed in incremental free recall, paired-associates learning, and cued and noncued recall of noun pairs. I n each case imagery had a clear positive effect on long-term retention, and the effect could not be explained by differential acquisition of the material. Results of the experiments were also examined by analyzing subjective organization, and by comparing cued and noncued recall. Such results were interpreted as supporting an imagery-organization hypothesis which asserts that images aroused by discrete verbal items can be combined into complex, integrated images, the components of which provide effective cues for retrieving or redintegrating the remainder of the unit.
The main purpose of this paper is to determine whether the familiar facilitatory effects of mental imagery on the acquisition of verbal material persist over a relatively long time interval. There is a dearth of experimental evidence germane to the question, and what little evidence there is is conflicting. Both Butter (1970) and Postman (1972) reported that the positive effect of imagery on learning became negative after a 1-wk retention interval, while Palermo (1970) and Yuille (1971) found that imagery effects were positive but considerably reduced in long-term tests of retention. Since existing imagery theories (e.g., Paivio, 1971) would be seriously compromised by a failure to find long-term effects of imagery, and since such failure would negate any potential practical implications of imagery in learning, it is of some importance to resolve the issue. Consequently three experiments were conducted to examine long-term free recall of nouns, long-term retention of paired-associates, and long-term
cued and noncued recall of noun pairs. In each case, nouns differing in image-arousing capacity were used as stimulus material. A second purpose of the paper is to present evidence related to the organizational properties of images in acquisition and retention. Begg (1972) suggested that imagery is an effective variable in recall largely because images can be readily combined into integrated subjective units. Each verbal item represented in such a unit is an effective cue for retrieving or redintegrating the remainder of the unit. In the first experiment in this paper, subjective organization was measured to determine whether imagery and long-term recall are related to such organization, and in the third experiment, cued and noncued recall were contrasted to determine whether imagery effects would be most pronounced in cued recall, both during acquisition and after a 6- to 10-day interval.
EXPERIMENT I z The research was funded by National Research Imagery has a clear facilitatory effect on Council of Canada Grant A8122 to the first author. The second experiment was conducted as an Indepenthe acquisition of nouns, whether defined by dent Study by Charles and Marian Winegard. The instructions to image (e.g., Gupton & Frincke, third experiment constitutes part of a Master's Thesis 1970; Kirkpatrick, 1894) or by ratings of by the second author. Reprints may be obtained from image-arousing capacity, concreteness, or Ian Begg, Department of Psychology, McMaster vividness (e.g., Dukes & Bastian, 1966; University, Hamilton, Ontario, Canada, L8S 4K1. Copyright © 1973by AcademicPress, Inc. 689 All rights of reproduction in any form reserved. Printed in Great Britain
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Paivio, 1968; Tulving, McNulty & Ozier, recall, particularly as related to imagery. 1965; Winnick & Kressel, 1965). Consequently That is, in the acquisition task, neither the it is difficult to equate learning of material recall data nor the organization data should differing in image-arousing capacity, in order contain main effects of imagery level, while in to conduct an unbiased test of the hypothesis the retention task, both dependent variables that imagery facilitates retention. Groninger should be positively related to imagery level. (1971) equated acquisition of lists of 25 highIn brief, two hypotheses were tested in the imagery nouns learned either by rote instruc- first experiment. First, more concrete than tions or imagery-mnemonic instructions by abstract nouns should be recalled on both the requiring a perfect recitation of each list. The 48- and 72-hr retention tests. Second, concriterion was reached more quickly by the crete nouns recalled contiguously on the imagery group than the control (14 versus 17 retention test should be more likely than min). After 1 and 5 wk, subjects again recalled abstract nouns recalled contiguously to have the lists. The imagery group enjoyed a 14~o been recalled in adjacent positions during the advantage at 1 wk, and a 19 ~o advantage after final acquisition trial. 5 wk, assessed by the total number of words recalled. In the present experiment, imagery Method was defined by using high- and low-imagery Subjects. Ten student volunteers from nouns as stimulus material, and an attempt McMaster University were each paid $5.00 was made to equate learning using a paradigm for their participation. Five subjects served described below. in each of two presentation orders. The procedure used in Experiment I was a Materials. Twenty-five concrete nouns (I > modified version of an incremental task repor- 6.00) and 25 abstract nouns (I < 3.60) were ted by Mandler and Dean (1969). On the first chosen from the Paivio, Yuille, and Madigan trial, the subject was presented with one word, (1968) norms. All nouns had frequencies of which he then recalled. On the second trial, A or AA. From the concrete words, one was the first word and a new word were presented randomly chosen as List 1. A second concrete and recalled. On each subsequent trial one word was chosen and added to List 1, which new word was added to the list, in a new ran- was subsequently reordered randomly, and dom order each time, and recall was requested, called List 2. Similarly, a third word was until on Trial 25, the subject attempted to chosen, and List 3 was constructed. The recall 25 words. procedure was followed until there were 25 The task was chosen for two reasons. First, lists of concrete nouns, ranging in length from there is no reason to expect differential one to 25 items. Twenty-five lists of abstract acquisition as a function of concreteness, nouns were also constructed using the same since performance is typically very good in the procedure. task and at least some items are overlearned. Procedure. The experiment was conducted Second, subjective organization can be mea- in three sessions for each subject. The first sured between successive written recall proto- two sessions were 24 hr apart, and the last cols to determine whether imagery is related two, 48. Half the subjects heard concrete to organization, and whether organization is lists during the first session and abstract during related to long-term retention. If, as Begg the second, while the reverse was true for the (1972) suggested, imagery is an effective remaining subjects. Each list was read to the variable in recall largely because images can subject at the rate of 4 sec per item, with an be readily combined into integrated subjective equal amount of time allotted for recall. Thus units, analyses of output-output organization a subject first heard one word, recalled it, then should provide results parallel to analyses of heard two words, recalled them, and so on
IMAGERY AND LONG-TERM RETENTION
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until the 25 lists had been presented and •where n is the number of words in common in recalled. Each of the first two sessions re- the two lists. The measure was calculated quired about 1 hr. In the final session, the starting with Trials 5 and 6, since the first subject was simply asked to recall as many trials have excessively high chance levels. The words from the first two sessions as he could in scores were averaged into four blocks of five 5 min. The subjects were given standard free trials each, and analyzed by a 2 x 2 × 4 recall instructions at the start of each session, analysis of variance with order, concreteness, and were not instructed that long-term recall and blocks as the factors. Concreteness interacted with order, F(1, 8 ) = 22.1, p < .01, would be required. since, as with the recall data, second-day Results and Discussion performance exceeded first-day performance Acquisition: Proportion correct. For each regardless of concreteness. For concrete subject, the proportions correct on the 25 nouns, the first and second day scores were trials were averaged over blocks of five trials .39 and .71, while for abstract they were .50 to obtain five scores within each level of and .59. By post hoc t tests, concrete nouns concreteness. These data were analyzed by a acquired on the second day were more organ2 × 2 x 5 analysis of variance, with order ized than those acquired on the first day (concrete on the first day, or abstract on the (p < .05), although neither differed reliably first day) as the independent factor, and con- from the amount of organization in the creteness (concrete or abstract) and blocks as abstract nouns. Thus the pattern of results repeated factors. The only significant main from the analysis of the organization data is effect was blocks, F(4, 32)=4.16, p <.01, similar to the results from the analysis of with respective means of 1.00, .95, .90, .93 and recall data. .94. Concreteness and order interacted, F(1, 8) Retention: Proportion correct. The pro= 9.37, p < .01, since second-day performance portions of words correctly recalled on the exceeded first-day performance regardless of retention testwere analyzed by a 2 x 2 analysis concreteness. For concrete words, the pro- of variance with order of presentation as an portions were .92 and .98, while for abstract, independent factor, and concreteness as a they were .92 and .95. The task thus yields repeated factor. Recall of concrete words performance data in which recall of concrete exceeded recall of abstract words, .72 versus and abstract words is equal on the first day, .54, F(1, 8)=17.3, p < . 0 1 . Concreteness and not very different on the second. As a interacted with order, F(I, 8) = 45.6, p < .01, further check on the equivalence of learning as shown in the left-hand panel of Figure 1. 2 o f the concrete and abstract nouns, perfor- A number of important points can be made mance in the final block of five trials was from the figure. First, the interaction clearly inspected separately. For the concrete and represents the fact that recall after 72 hr (the abstract nouns learned on the first day, bottom two points in the figure) was lower than performance was at .87 and .93, respectively, recall after 48 hr. Note also that the facilitawhile both were recalled at .99 on the second. tive effect of imagery does not diminish over Consequently, any retention differences as a the interval: at 48 hr, concrete nouns enjoyed function of imagery cannot be attributed to an advantage of .18 (.87-.69), and at 72 hr differential acquisition levels. the advantage was also .18 (.58-.40). By post
Acquisition:
Output-output
organization.
Organization was measured by Mandler and Dean's (1969) ITR(2), defined as the number of bidirectionally co-occurring pairs in two successive output protocols, divided by n-l,
The figures are plotted by retention interval rather than by order, although the results were analyzed by order. The subjects represented by the top-left and bottom-right points received concrete items on the first day.
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Fro. 1. Recall and organization of concrete and abstract nouns after a 48- or 72-hr delay.
hoc t tests, the imagery effect was reliable at both delays, and 72-hr recall was worse than 48-hr recall within both levels of concreteness (ps < .05). Retention: Output-output organization. The ITR (2) measure was computed between the last recall trial during acquisition and the longterm recall protocol. The results were analyzed by a 2 × 2 analysis of variance, with factors as above. Concrete lists were more organized than abstract, .52 versus .27, F(1, 8) =25.7, p < . 0 1 . Concreteness and order interacted, F(1, 8 ) = 50.2, p < .01, as shown in the right-hand panel of Figure 1. The interaction resembles the interaction in recall data at the longer term, just at it did during acquisition. Post h o c t tests revealed that 72-hr recall was less organized than 48-hr recall at both levels of concreteness, and that concreteness was positively related to organization at both delay intervals (ps < .05). The data support two strong conclusions.
First, concreteness is a powerful variable in retention of nouns, even in a situation where no facilitation is afforded concrete nouns in acquisition. Taking Groninger's (1971) results into account, it is clear that mental imagery facilitates long-term retention of words, and the effect does not diminish over the time intervals used in these experiments. Second, concreteness and organization are highly related, both during the acquisition and long-term retention of words. Although the present data do not justify inferences of causality between the two variables, the relation can be predicted from an imagery-organization hypothesis outlined by Begg (1972, 1973), who argued that images aroused by concrete words could be organized into complex images in memory, and that retrieval of part of the compound image would provide subjective cues for retrieving or redintegrating the rest of the image, with contingent enhancement of recall. If the hypothesized subjective organiza-
IMAGERY AND LONG-TERM RETENTION
tion and redintegration occur, high intertrial output organization should be apparent, as in the present experiment. EXPERIMENT I [
The second experiment investigated the fate of imagery effects in paired-associates learning, with a 72-hr delay between the last acquisition trial and the retention test. The effect of imagery in paired-associates learning is well documented (see Paivio, 1969, 1971), with the greatest facilitation due to imagery in the cue members of the pairs (stimuli), although imagery level also affects recall of the to-be-remembered items (responses). The question of interest is whether the imaginal facilitation of paired-associates learning persists over longer periods of time. Butter (1970) reported an experiment in which, among other things, subjects read noun-digit pairs which they subsequently recalled after 2 min, 20 rain, or 2 days. She found that although word concreteness was positively related to digit recall after 2 min, the effect was virtually absent after 20 min, and was strongly reversed after 2 days. Over the range of the experiment, the recall of digits associated with concrete nouns declined to about a third of the short-term level, while surprisingly, the recall of digits associated with abstract words doubled between 2 min and 2 days. However, Yuille (1971) repeated the experiment and failed to replicate the concreteness reversal. In his experiment the concreteness effect was strong after 2 min, and was still positive, although nonsignificant after 2 days. Yuille (1971) also reported data from two other experiments in which subjects learned paired-associate lists containing the four combinations of concrete (C) and abstract (A) stimulus and response terms. In both experiments and at both 0- and 1-wk delays, the order of conditions with respect to the number correct was CC, CA, AC, and AA, the usual order. Adding over the two experiments, it is
693
possible to estimate the size of the effect of imagery both on the stimulus side (CC + CA AC - AA) and the response side (CC + AC - C A - AA). The stimulus effect at shortterm (14.2) was slightly larger than the response effect (12.6). At the longer delay, the stimulus effect (7.5) was still greater than the response effect (3.5), although both were reduced considerably, being 53 ~ and 28 of their respective former values. Similarly, Palermo (1970) reported that the stimulus imagery effect was 50 ~ of its former value after a 2-day delay, while Schnorr and Atkinson (1969) found the facilitation due to imagery instructions still present after a week, but at a reduced level. The method of estimating the size of the concreteness effect used above is open to criticism. Since memory decay is typically of some geometric or exponential form (e.g., Wickelgren, 1970), conditions starting at relatively higher performance levels would decline over time relatively faster than conditions starting at lower levels, if the amount of decline is expressed in absolute terms. However, if the decline is expressed proportionally, this may not be the case. For Yuille's (1971) data, each of the remaining three conditions can be expressed as a proportion of performance in the CC condition, both in the immediate and delayed tests. When the imagery effects are calculated as above, but using proportions, the short-term stimulus and response imagery effects are .51 and .45, respectively, compared with their respective long-term values of .77 and .35. Thus the stimulus imagery effect at the longer delay is 151 ~o of its short-term value, and the response imagery effect is 78 ~o of its former value. Schnorr and Atkinson's long-term effect is 40~o with the arithmetic calculation while with ratios it is 76 ~ of the short-term effect. Therefore, it can be concluded that the diminution of the imagery effect over time is largely a function of the way in which the effect is measured. Perhaps the least controversial assessment o f the size of the effect -
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would be to convert scores at both the shortand long-term to z scores. However, a better way of examining the effects would be to use tasks in which concrete and abstract items do not differ in acquisition, so that differences in long-term recall can be assessed directly. Postman (1972) reported an experiment in which CC, CA, AC, and AA noun pairs were learned to the criterion of 12 of 16 pairs correct. The respective pairs required 4, 6, 9, and 13 trials to reach criterion. After 1 wk, memory for the pairs was again assessed. In terms of losses from projected scores, the order of conditions on the first long-term test trial was AC, CA, AA, and CC, although by the second test trial the middle two conditions had reversed. Since the ordering of conditions is highly discrepant from any predicted order based on theoretical accounts of imagery, it is important to determine whether the reversal of the imagery effect is due to some aspect of the experiment or due to imagery per se. It is unlikely that the reversal could result from differential accessibility of the individual words, since imagery is positively related to long-term retention of words (Experiment I; Groninger, 1971). The clue to understanding the reversal more likely lies in the associative phase of the task; that is, perhaps imagerymediated associations are more vulnerable to interference or decay than other associations over the time period of interest. However, before explaining the reversal, it is desirable to see whether the effect can be replicated. In the second experiment, subjects learned paired-associates consisting of either CC or AA pairs. The pairs were presented in either 16- or 50-item lists, and were learned to a criterion of 50 70 correct, 75 ~ (76 70 for the 50-item list) correct, or 100 K correct. Procedural differences between the present experiment and Postman's experiment require explication. First, short and long lists were used since in Postman's 16-item list the difference in number of trials to criterion between the CC and AA lists (4 versus 13) was proportionately very large. Second, three
different criterion levels were used simply for their parametric value. The third major difference is that as a subject correctly anticipated a response, that pair was dropped from the list. Thus the present experiment controlled the number of correct recalls for CC and AA pairs, while Postman's experiment controlled the proportion of the list recalled. A problem with the latter procecure is that despite the equality of criterion performance, there can be a wide disparity in the number of times a given pair is correctly recalled. To illustrate with Postman's data, if we assume the number of items recalled on a given trial is a linear function of the number of presentations, then 30 CC items were correctly recalled over the four trials required to reach the criterion of 12 items correct, and 84 AA items were correctly recalled. Since it is not unreasonable to expect that long-term recall is positively related to the number of shortterm recalls, Postman's results could reflect this contaminating variable rather than concreteness. Thus, for the present purposes, it was deemed desirable to equate the number of correct anticipations rather than to equate list performance. Method Subjects. Sixty students from McMaster University were paid $2 per hour for their participation in the experiment. Five subjects served in each of 12 groups. Materials. One hundred concrete (I ~>6.00) and 100 abstract (I ~<3.90) nouns were selected from the Paivio et al. (1968) norms. Frequency levels were roughly equated, with all frequencies greater than 15, and most A or AA. The 100 concrete nouns were randomly assigned to 50 pairs, as were the abstract. For the short lists, 16 concrete and 16 abstract pairs were selected from the 50, again with frequency controlled. Each pair was typed on an index card, with one word on each side. Procedure. The basic design was a 2 x 2 x 3 factorial, with independent groups. Thus there were concrete and abstract lists, short
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and long lists, and 50, 75, and 100 ~ criterion levels. In any given condition, a subject was presented with a deck of cards. On the first trial, the experimenter read aloud the nouns on the front and back of the cards, while the subject watched. The cards were then shuffled and given to the subject, who attempted to anticipate the noun on the back of the card, and then turned the card over. If the anticipation was correct, the card was removed from the deck. At the end of each run through the deck, the remaining cards were reshuffled and handed back to the subject. Acquisition stopped at the response which met the criterion. For the retention test, subjects were recalled after 72 hr, and were shown and read the noun on the front of each card. They attempted to anticipate the second member of the pair on one trial. All presentations in each phase of the experiment were self-paced, although subjects took about 5 sec per card. Results and Discussion The number of pairs correctly anticipated at the long term were analyzed separately for the short and long lists, in each case by a 2 × 3 analysis of variance, with concreteness and criterion level as independent factors. For the short list at the long delay, more concrete than abstract pairs were correctly anticipated, 6.00 versus 3.47, F(1, 24) = 9.53, p < . 0 1 . There was also a main effect of criterion level, F(2, 24) = 3.99, p < .05. Post hoc t tests were performed on the data, with the following conclusions. More concrete than abstract pairs were correctly anticipated in both the 75 and 100 K criterion groups (ps < .05), but not in the 50 ~ group. For the abstract pairs, there were no differences in long-term recall as a function of criterion group, while for concrete pairs, the 5 0 ~ group led to lower levels of performance than the other two conditions (ps < .05), which did not differ from each other. There is thus one conclusion. Concreteness is positively related to long-term retention when the number of correct anticipations is controlled
during acquisition, except when the original criterion is lenient (50 7oo). The results for the longer list were similar. More concrete than abstract pairs were correctly anticipated, 20.5 versus 11.5, F(1, 24) =23.0, p < .001, and long-term performance increased with stringency of criterion, F(2, 24) = 22.9, p < .001. The variables interacted, F(3, 2 4 ) = 6.28, p < .01, as shown in Figure 2. As in the short list, concrete pairs i~
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led to better recall than abstract at both the 75 and 100 ~ criterion levels (ps < .05) but not at the 50~o level. In concrete pairs, each increase in stringency of criterion led to an increase in recall (ps < .05), while in the abstract pairs, only the 100 ~ and 50 ~o criteria led to reliably different long-term performance. The results of the experiment are straightforward. Imagery facilitates retention over a 72-hr delay when recall is equated at acquisition, unless the equation is at a relatively low
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level. Concrete items benefit disproportionately from increased stringency during acquisition, despite the fact that concrete and abstract pairs were initially recalled equally often. Finally, the above-mentioned effects are stronger when the lists are longer. EXPERIMENTIII The purpose of the third experiment is to extend the results obtained in the first two experiments, as well as to test some predictions derived from a theoretical account of imagery facilitation. First, the question of central importance in this paper concerns long-term imagery effects, and as a result, the experiment investigated long-term memory for noun pairs, in a task designed to emphasize the pairness of the items. Second, both cued and noncued recall of the pairs were collected at acquisition and after a delay of 6-10 days. If imagery effects in long-term memory are qualitatively similar to effects in short-term memory, then effects found by Begg 0972, 1973) should be observable after the delay. That is, the facilitative effect of cueing should be more pronounced with concrete than abstract pairs at both acquisition and retention. Likewise, in noncued recall, a higher proportion of concrete than abstract nouns recalled should be in pairs, regardless of whether the recall is at short- or long-term. In the third experiment, then, subjects were presented with concrete and abstract noun pairs for five trials. On each trial, they were instructed to form either imaginal or verbal mediators for each pair. Latencies were recorded. After the fifth trial, subjects were tested for either cued or noncued recall of the pairs. The subjects were again tested after 6-10 days. Method Subjects. Thirty-two student volunteers from McMaster University were paid $2 per hour for their participation, with eight subjects in each factorial combination of set
(imagery or verbal) and cueing (present or absent). Materials, Sixty high-imagery (•>6.00) and 60 low-imagery ( I < 3.90) nouns were selected from the Paivio et al. (1968) norms, with frequency values of A or AA for all but four nouns of either set. Thirty high-imagery and 30 low-imagery pairs were selected randomly. Each pair was typed in upper case on an index card. Procedure. The cards were presented tachistoscopically, to the right of a fixation point. The subjects initiated each exposure by pressing a button, which also started a timer, and terminated the trial by releasing the button upon completion of the processing required by the instructions. Half the subjects were given imagery mediation instructions, and half were given verbal. After releasing the button, subjects described their mediators. Each subject received the 60 pairs in a different random order in each of five trials. They were instructed to try to use the same mediator on each trial, but to generate a new one if they could not recall the old one. After the fifth trial, subjects within each group were randomly assigned either to a cued or noncued recall condition. For cued recall, response sheets were provided on which one member of each pair was typed, and the subject was asked to fill in the missing words. Right- and left-hand members served as cues equally often. For noncued recall, the subject was asked to write down as many words or pairs as he could. After a delay of 6 days, subjects were mailed or given response sheets identical to those filled out in immediate recall and were requested to fill them out again. If replies were not returned within 3 days, subjects were contacted by telephone. All subjects replied between 6 and 10 days of the previous test. Results and Discussion Mediation lateneies. Mean latencies were calculated for each subject on each trial, for both concrete and abstract pairs. Because of
IMAGERYAND LONG-TERMRETENTION large discrepancies in the variances, each trial was separately analyzed by a 2 × 2 analysis of variance, with set (imagery or verbal) as an independent factor, and concreteness as a repeated factor. All F ratios had df= 1, 30. On the first trial, verbal instructions led to shorter latencies than imagery instructions, 6.12 versus 10.4 sec, F = 4.20, p < .05, but the effect was not reliable on any later trial. The interaction between the variables was not reliable on any trial. The concreteness effect, however, was highly reliable on every trial, p < .001, with respective Fs of 21.0, 38.0, 42.9, 60.8, and 74.4, with concrete pairs associated with shorter latencies than abstract pairs. Word recall. As a preliminary analysis, the numbers of words correctly recalled in each of the four combinations of cueing (present or absent) and time (short term or long term) were analyzed by a 2 x 2 x 2 analysis of variance, with set (imagery or verbal) as the independent factor, and concreteness (concrete or abstract) and term (stimulus or response) as repeated factors. More concrete than abstract words were recalled (p < .01) in each of the four analyses. More stimulus than response terms were recalled in the cued longterm condition (p < .01), while recall in the other three conditions was symmetrical. No interactions nor effects of set were significant in any of the analyses. Because of the results of the preliminary analysis, the major analysis of word recall was a 2 x 2 x 2 analysis of variance, with cueing (present or absent) as the independent factor, and concreteness (concrete or abstract) and time (short-term or long-term) as repeated factors. The proportion of items correct was the dependent measure, since there were potentially twice as many correct items in the noncued conditions as in the cued conditions. All three main effects were reliable (df= 1, 30; ps < .001), with cued recall exceeding noncued recall, .69 versus .49, F = 2 1 . 7 , recall of concrete items exceeding abstract, .71 versus .45, F = 60.1, and short-term recall exceeding
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long-term recall, .70 versus .46, F = 6 4 . 0 . The effects of cueing and concreteness were not independent, since the two variables interacted, F = 4.29, p < .05. The interaction reflects the fact that the facilitative effect of concreteness was greater in cued than noncued recall, or alternatively, the effect of cueing was greater with concrete than abstract pairs, resulting in disproportionately high cued recall of concrete nouns. Concreteness also interacted with time, F = 86.5, p < .001. The concreteness effect was larger at the long-term than the short-term, since more abstract than concrete items were forgotten over the interval between tests. All the above effects were slightly qualified by the three-way interaction, F = 30.1, p < .001, shown in Figure 3. The facilitative effect of cueing was very small in the long-term recall of abstract pairs, but present in the other three comparisons. The
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effects of time and concreteness are minimally qualified by the interaction. Additionally, the two-way interaction of concreteness with cueing, although present in absolute terms in both long- and short-term performance, was more pronounced at the longterm. Finally, the Concreteness x Time interaction was more pronounced in cued than noncued recall. With respect to word recall, then, the facilitative effect of imagery increases over time, and is greater in cued than noncued recall at each level of time. The first finding is completely in line with the results from the first two experiments, and the second is consistent with the results reported by Begg (1972, 1973). Pair recall. The number of pairs correctly recalled in noncued recall was analyzed by a 2 x 2 x 2 analysis of variance, with set (imagery or verbal) as the independent factor, and concreteness (concrete or abstract) and time (short- or long-term) as repeated factors. More concrete than abstract pairs were recalled, .56 versus .35, F(1, 14)=17.8, p < .001, and short-term retention was superior to long-term, .55 versus .35, F = 22.5, p < .001. The two variables did not interact, but, if anything, the concreteness effect was larger at the long term (.45 versus .24) than at the short term (.65 versus .47). Once again, there is no hint of a diminution of the effectiveness of imagery over time. Conditionatprobabilities. For each subject, two ratios were calculated: The number of stimulus terms recalled was divided into the number of pairs recalled, and the number of response terms recalled was divided into the number of pairs recalled. The proportion of words recalled that were in pairs (the mean of the two ratios) was analyzed by a 2 × 2 × 2 analysis of variance, with the same factors as above. The conditionals associated with concrete phrases were higher than those with abstract, .947 versus .805, F(1, 14)= 8.00, p < .025, and the concrete conditionals diminished less over time than did the abstract, F = 4.81, p < .05. The respective short- and
long-term values for concrete pairs were .969 and .925, while for abstract they were. 853 and .756, Conditional probabilities, calculated as above, are also higher for meaningful concrete than abstract phrases (Begg, 1972), and for concrete noun pairs learned under interactive rather than separated imagery instructions (Begg, 1973). As a generalization, it seems that tasks or items designed to emphasize pairness are characterized by higher conditional probabilities than those that are not, although the relation is not statistically necessary. Long-term recall conditionalized on shortterm recall. Since initial recall levels were higher for concrete than abstract pairs, longterm recall was examined for pairs at given levels of short-term recall. In cued recall, 76 ~o of the concrete pairs correct at short-term were also recalled at long-term, while for abstract, only 40 ~o of such items were recalled at long-term (p < .001). In noncued recall, several short-term levels of performance were isolated, and long-term recall examined. First, pairs correctly recalled at short-term were considered. Of words in such pairs, 60 ~ of concrete and 45 ~ of abstract (p < .001) were also recalled at long-term. Second, for pairs in which only one item was recalled at shortterm, 5 2 ~ of concrete and 1 4 ~ of abstract words (p < .001) were recalled at long-term. Finally, for unrecalled pairs at short-term, 30 Yo of concrete and 18 ~ of abstract words were recalled at long-term (p < .02). Thus the differential levels of recall in the long-term condition cannot be attributed to differential recall of concrete and abstract words at the time of acquisition. GENERAL DISCUSSION Because of the quantity of data presented, a summary is in order. First, considering longterm recall, it is safe to conclude that imagery facilitates retention. In Experiment I, more concrete than abstract nouns were recalled after 48 and 74 hr, despite the fact that
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acquisition did not favor the concrete nouns. In Experiment II, more concrete than abstract responses were correctly anticipated after 72 hr when acquisition was controlled at 75 or 100 ~o correct anticipations. In Experiment III, several results support the conclusion. In both cued and noncued recall, more concrete than abstract words were recalled after a week, and the effect could not be attributed to differential acquisition, since the long-term imagery effect was larger than the short-term effect, and was strong even in concrete and abstract pairs that were equally well recalled at the short term. Further, more concrete than abstract pairs were recalled in long-term noncued recall, and again the effect was larger at long than short term. Finally, concrete words recalled in long-term noncued recall were more likely to be in pairs than were the abstract words, and the difference was larger after a week than at the time of acquisition. Because of the difficulty of controlling acquisition levels of concrete and abstract materials, each of the three experiments is open to criticism for failure to equate learning on some basis. However, the overall conclusion based on the very different techniques employed is unshakeable: Imagery facilitates retention as well as acquisition. A second class of conclusions is of more theoretical importance, and concerns integration as a concept. Begg (1972, 1973) argued that the usual imagery effect is largely a function of the fact that images aroused by discrete verbal items can be combined into complex images which operate as units in memory, being remembered or forgotten as units, and with each component of the image serving as an effective cue for redintegrating the rest of the unit. In the first experiment, the facilitative effects of imagery in retention were closely paralleled by changes in the amount of subjective organization used by subjects. In the third experiment, imagery effects were more pronounced in cued than in noncued recall, and even in noncued recall members of concrete pairs were more likely to share a
c o m m o n fate in memory than were members of abstract pairs. Consequently, the integration hypothesis is supported as an explanation ofimaginal facilitation of acquisition, and is extended as an explanation of imagery effects in longer-term retention. Thus we conclude that imagery facilitates retention, and we suggest that the integrative properties of images are responsible for the effect. REFERENCES
BraG, I. Recall of meaningful phrases. Journal of Verbal Learning and Verbal Behavior, •972, 11, 431-439. BEOG,I. Imagery and integration in the recall of words. CanadianJournalof Psychology, 1973,27,159-167. BUTTER,M. J. Differential recall of paired associates as a function of arousal and concreteness-imagery levels. Journal of Experimental Psychology, 1970, 84, 252-256. DUKES, W. F., & BASTIAN,J. Recall of abstract and concrete words equated in meaningfulness. Journal of Verbal Learning and Verbal Behavior, •966, 5, 455-458. GRON~NOER,L. D. Mnemonic imagery and forgetting. Psychonomic Science, 1971, 23, 161-163. GtrPTON, T., & FRINCKE, G. Imagery, mediational instructions, and noun position in free recall of noun-verb pairs. Journal of Experimental Psychology, •970, 86, 461-462. KIRKPATRICK,E. An experimental study of memory. Psychological Review, 1894, 1,602-609. MANDLER, G., & DEAN, P. J. Seriation: Development of serial order in free recall. Journal of ExperimentalPsychology, •969, 81,207-215. PAIVIO,A. A factor-analytic study of word attributes and verbal learning. Journal of Verbal Learning and VerbalBehavior, •968, 7, 41-49. PAWIO,A. Mental imagery in associative learning and memory. PsychologicalReview, 1969, 76, 241-263. PAIVIO,A. Imagery and verbalprocesses. New York: Holt, Rinehart & Winston, 1971. PAWIO, A., YU~LLE,J. C., & MADMAN, S. A. Concreteness, imagery, and meaningfulness values for 925 nouns. Journalof ExperimentalPsychology, Monograph Supplement, 1968, 76 (1, Pt. 2). PALERMO,D. S. Imagery in children's learning: Discussion. PsychologicalBulletin, 1970, 73, 415-421. POSTMAN, L. The experimental analysis of coding processes. Paper presented at the Midwestem Psychological Association Meetings. Cleveland, 1972.
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SCHNORR,J. A., & ATK1NSON,R. C. Repetition versus imagery instructions in the short- and long-term retention of paired-associates. Psychonomic Science, 1969, 15, 183-184. TULVING,E., McNULTY,J. A., & OZIER,M. Vividness of words and learning to learn in free-recall learning. Canadian Journal of Psychology, 1965, 19, 242-252. WICK~LGREN, W. A. Multitrace strength theory. In Norman, D. A. (Ed.) Models of human memory. New York: Academic Press, 1970.
WINNICK, W. A., t~ KRESSEL, K. Tachistoscopic recognition thresholds, paired-associate learning, and immediate recall as a functionof abstractnessconcreteness and word frequency. Journal of Experimental Psychology, 1965, 70, 163-168. YUILLE,J. C. Does the concreteness effect reverse with delay2 Journal of Experimental Psychology, 1971, 88, 147-148.
(Received June 8, 1973)