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Two developmental transitions in selective remembering strategies
JOURNAL
OF EXPERIMENTAL
CHILD
PSYCHOLOGY
36, 43-55 (1983)
Two Developmental Transitions in Selective Remembering Strategies NORMAN W. BRAY The University of Alabama
ELAINE M. JUSTICE Old Dominion University AND DAVID N. ZAHM University of Cincinnati Two experiments were reported investigating developmental changes in the use of strategies to eliminate interference from irrelevant information in memory. The participants in the first were 7-. 9-, and 1 l-year-old children and those in the second were adults. In both experiments a directed forgetting paradigm was used in which the person was presented two sets of pictures but only recalled one set on a trial. On some trials there was a cue to forget the first set and to remember only the second set. There were two developmental transitions. The first was from ineffective to effective selective remembering which occurred between 7 and 11 years of age. The second, which occurred between 11 years of age and adulthood, was from the use of selective retrieval strategy to a more sophisticated rehearsal strategy. The implications of these two developmental transitions were discussed.
An important part of cognitive development is the increasing ability of the child to respond to task-relevant stimuli and to disregard irrelevant stimuli (Gibson, 1969; Hagen & Stanovich, 1977; Wright & Vlietstra, The cooperation of the principal, faculty, and students of Houston Elementary School is gratefully acknowledged. The first experiment reported was completed in partial fulfillment of the Master of Arts Degree by David Zahm in the Department of Psychology, University of Cincinnati, under the supervision of Norman Bray. This research was supported by NIH Research Grant HD 15669 from the National Institute of Child Health and Human Development, first author Principal Investigator. Requests for reprints should be sent to Norman W. Bray, Department of Psychology, Box 2968, The University of Alabama. University, AL 35486. 43 0022-0965183 $3.00 Copyright 0 1983 by Academic Press. Inc. All rights of reproduction in any form reserved.
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1975). One aspect of selectivity which has received relatively little research attention is the ability to select relevant information and to disregard irrelevant information already stored in memory (Bray, 1979). The ability to disregard information in memory has usually been studied in a directed forgetting paradigm in which the person is occasionally given a cue to forget information previously presented. In order to assure that the person tries to remember all the information until a cue to forget is given, frequent control trials with no forget cue are included. Effective directed forgetting is indicated when the functional memory load is determined by the number of to-be-remembered items and is independent of the number of to-be-forgotten items. Numerous studies have found that adults spontaneously adopt strategies that eliminate interference from irrelevant information (see Bjork, 1972; Epstein, 1972; MacLeod, 1975 for reviews). Bjork (1972) found that effective directed forgetting depends on two interrelated factors: (a) the use of selective rehearsal and (b) differentiation of the to-be-forgotten and to-be-remembered items in memory. In selective rehearsal all items are rehearsed until a cue to forget is given, but following a cue, rehearsal of the to-be-forgotten items is terminated and all further processing is devoted to the subsequent to-be-remembered items. Differentiation refers to the functional separation of to-be-forgotten and to-be-remembered items which may occur as a result of selective rehearsal. Although there have been no developmental studies of directed forgetting, the results of two studies with young children indicate that marked developmental changes can be expected. Howard and Goldin (1979) used a version of the directed forgetting paradigm in which some kindergarten children were given a precue concerning the information to be forgotten. Others were given a regular directed forgetting task in which the cue occurred following the presentation of the to-be-forgotten items. With the precue, kindergarten children had no difficulty disregarding the irrelevant information. Without the precue the irrelevant information interfered with recall of the to-be-remembered items. Bray and Ferguson (1976) tested first-grade children in a directed forgetting task in which the forget cue occurred within a sequence on some trials. There were frequent control trials with no forget cue. First-grade children processed the items following a forget cue more actively than the items before a forget cue. Bray and Ferguson noted that this strategy was considerably less sophisticated than the one described by Bjork (1972) and presumably used by adults. The studies with children (Bray & Ferguson, 1976; Howard & Goldin, 1979) and those with adults (Bjork, 1972) present an interesting (but incomplete) picture of developmental changes in the ability to disregard irrelevant information in memory. Kindergarten children can disregard information if given a cue before the information is presented. but not once the items have been processed. First-grade children adopt relatively
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unsophisticated strategies and adults use strategies that minimize interference from the to-be-forgotten material. Two experiments are reported here which were designed to provide a clearer understanding of developmental changes in directed forgetting performance and changes in the nature of the strategies used. The task consisted of five trial types in which the participant was requested to remember a set of picture names. On forget trials four pictures on a yellow background and then four pictures on a blue background were presented, but only the blue pictures were tested. Thus the color change was a signal to forget the previously presented yellow pictures. On Probe 1 and Probe 2 trials, eight yellow pictures were presented for study. The first four were tested for recall on Probe 1 trials and the last four on Probe 2 trials. On precued and control trials only four pictures were presented. On precued trials the participant was given a cue that only four pictures would be presented and then tested. On control trials there was no precue. ’ Effective directed forgetting would be indicated if two results were obtained. First, recall accuracy should be higher on forget than on Probe 2 trials, indicating a facilitation due to the forget instruction. Second, recall accuracy on forget, precued, and control trials should not differ, indicating that the facilitation provided by the forget instruction was due to the elimination of interference from the to-be-forgotten material. Because Bjork (1972) suggested that rehearsal was an important aspect of an effective directed forgetting strategy, the pause time procedure of Belmont and Butterfield (1971a, 1971b) was used to monitor the type of acquisition strategy. If selective rehearsal is used, the length of pauses between items should increase as pictures are presented. Following a forget cue the pause time should be “reset” to its original level and then increase again as the subsequent pictures are presented. In the first experiment, developmental changes in directed forgetting performance (accuracy) and the nature of the directed forgetting strategy (pause time) were examined in 7-, 9-, and 11-year-old children. In the second, the same aspects of directed forgetting were examined in adults. EXPERIMENT
1
Method Subjects. The participants were 48 children, 16 each from the first-, third-, and fifth-grade classrooms in two different schools in Cincinnati, Ohio. There was an equal number of boys and girls in each age group with mean ages of 7.0 (SD = .3), 9.2 (SD = .4), and 11.0 (SD = .2). All students were in their age appropriate grade placements. ’ As explained in detail in the method section, the color backgrounds were counterbalanced so that the initial color (yellow or blue) could not be used to determine the trial type.
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Stimulus materials. The stimuli were twenty-two 2 x 2-in. (5.08 x 5.0%cm) slides of black on white line drawings of common objects such as ball, chair, table, and hat. Each stimulus was photographed on 35mm transparency film. These stimuli were similar to those used in previous studies of directed forgetting in children (e.g., Bray, 1979). Apparatus. The main components of the apparatus was a lo-window rear projection device (Model MPRO-310, Behavior Apparatus Builders). The windows measuring 1.75 x 2.00 in. (4.45 x 5.08 cm) were arranged in a single row at the front of the projection device. The front was covered with a black mat board facing with openings for Windows 1-8. A strip of .50-in. (1.27-cm) white tape divided the display into two sets of four windows each. Below each window was a button which the child pressed to expose a stimulus. Each window could be illuminated individually by either a projection lamp, which displayed a picture, or by a probe lamp, which illuminated the window without projecting a picture. An eight-channel paper tape reader (Model TPI UR, Behavior Apparatus Builders) was used to control the projection device. A printing clock counter was used for recording interitem pause times (Model PR210A. Behavior Apparatus Builders). Procedure. All children were tested individually in a mobile laboratory parked on the school grounds. This laboratory was divided into two rooms so that the control equipment was isolated from the child. There was one pretraining session and one experimental session separated by about 48 hr. In order to assure that the pictures could be identified, each child was required to name the pictures prior to beginning the pretraining. None of the children had difficulty with this task. Following the stimulus familiarization, the child was trained on the pause time procedure. This consisted of six trials in which the number of pictures was gradually increased from two to four. The sequence of events was as follows: The child pressed the button below the first window and the stimulus was projected in the window for 1 set; there was a subject-determined pause; the second button was pressed: the second picture appeared. This procedure was repeated for the remaining pictures on a trial. There was a I-set retention interval following the last button press: for 10 set a probe lamp illuminated the window of the picture to be recalled. Successive pictures were tested, in order, in this manner, beginning with Picture I on Control 1 and Probe 1 trials and Picture 5 on Forget, Precued, and Probe 2 trials. This was followed by an experimenter-paced intertrial interval. If the child gave a picture name (correct or incorrect) during the IO-set recall interval for a given probe, the experimenter immediately advanced the apparatus to the next probe. Over the next five trials the number of study items was gradually increased from four to six to eight. On these trials the child was tested on either the first half (Probe 1) or the second half (Probe 2) of the items presented. For instance, if four pictures were presented, either the first
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two or the last two were tested. The children were instructed to try to remember all the pictures since they were not told which set would be tested on a particular trial. On the Probe 1 and Probe 2 trials all of the pictures had either a blue or yellow background. The signal to forget procedure was then introduced. The children were instructed that when the background color changed (yellow-blue or blueyellow), only the second color pictures would be tested. This meant that they could forget the items presented before a color change. It was also stressed that since there were trials with no color change, they should try to remember all items until a color change occurred. Following the forget trials, control and precued trials were introduced. On control trials four pictures were presented in Windows l-4 and tested. On precued trials the equipment did not operate when the child pressed the first button. This was a cue to press the fifth button. The four pictures for that trial were then viewed in Windows 5-8. The first button was operative for all other trial types. At the beginning of the experimental session there was a review of the trial types, two warm-up trials consisting of one Probe 1 trial and one precued trial, and a comprehension test. In the comprehension test, the children were asked to explain what to do when they saw pictures on a yellow background in the first four windows and pictures with a blue background in the last four windows. Likewise they were asked what it meant and what to do when they saw pictures with all the same background color. All but one child answered the comprehension test questions correctly. The one child who failed this comprehension test (a 7-year-old) was excluded and replaced. Following the comprehension test there were 24 experimental trials which included six forget trials, five trials each for the control and precued trials, and four trials each on Probe 1 and Probe 2 trial types. Four different presentation orders were used to balance the presentation order of the trial types and to assure that each picture was used in each trial type approximately equally often. Results Accuracy analysis. A response was scored as correct when the picture recalled was the same as the picture which appeared in the window probed. The proportion of correct responses was computed for each child at each serial position by collapsing over trials on each of the five trial types.’ All post hoc tests were conducted with the Newman-Keuls procedure (CI = .05). ’ For each of the analyses of variance on proportion correct responses reported in this paper, identical analyses were performed on an arc sine transformation. Because the pattern of results in both sets of analyses was the same in all cases. only the analyses on proportion correct are reported.
BRAY, JUSTICE,
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AND ZAHM
The analysis of variance included age (7, 9, and I I years old), sex (2), trial type (forget, control, precued, Probe 1, and Probe 2), and serial position (one through four), where the latter two factors were withinsubjects variables. There were significant main effects for age. F(2, 42) = 8.83, p < .Ol; trial type, F(4, 168) = 4.55, p < .Ol; and serial position, F(3, 126) = 3.58, p < .Ol. The means for the 7-, 9-, and 11-year-olds were .26, .44, SO, respectively. Post hoc tests indicated equivalent recall for 9- and 1 l-year-old children with both groups higher than the 7-yearolds. For the precued, control, forget, Probe 2, and Probe 1 conditions the means were, in order: .57, .49, .48, .29, and .20. Newman-Keuls tests indicated the following pattern of differences: precued > (forget = control) > Probe 2 > Probe 1. The means for serial Positions l-4 were .56, .45, .35, and .30, respectively. All serial positions were significantly different from each other. There was a significant interaction between trial type and age, F(8, 168) = 4.63, p < .Ol. The means for this interaction are shown in Table 1. There was no facilitation due to the forget cue in the 7-year-olds with accuracy on forget trials equal to accuracy on Probe 2 trials. Recall accuracy on control trials was equal to accuracy for precued trials. Accuracy for control and precued trials was greater than recall accuracy on both probe trials. The 9-year-old children demonstrated some facilitation due to the forget cue. Accuracy on forget trials was equal to that on control trials and greater than accuracy on Probe 2 trials. However, performance on precued trials was significantly better than recall on forget trials. The 1 I-year-olds demonstrated more effective performance on the directed forgetting task. The cue clearly facilitated performance. Recall was greater on forget trials than on Probe 2 trials and equal to that obtained on both control and precued trials. The pattern of differences for the 1 l-year-old children was as follows: (forget = control = precued) > (Probe 2 = Probe 1). There was also a significant interaction between serial position and age, F(6, 126) = 2.44, p < .05. All three age groups showed marked TABLE MEAN
PROPORTION
1
CORRECTLY
RECALLED
Age group Trial type Forget Premed Control Probe I Probe 2
7 years
9 years
11 years
Adults
.27 .33 .34 .16 .20
.51 .65 .51 .18 .35
.66 .72 .62 .26 .32
.83 .83 .85 .49 .60
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REMEMBERING
primacy effects. However, 9-year-old children demonstrated a more distinct recency effect than the other groups. The only other significant interaction was between trial type and serial position, F(12, 504) = 4.18, p < .Ol. Recall on forget, control, and precued trials was not significantly different at the first two serial positions. At the last two serial positions, however, recall accuracy was greater on precued than on either forget or control trials. Across serial positions, recall on Probe 1 and Probe 2 trials was consistently less than accuracy on the other trial types. Pause time analyses. The pause time measure was the median pause time for each child at each serial position. For the purposes of this analysis the median pause time for the Probe trials was based on the combined Probe 1 and Probe 2 pause times, thus increasing the number of observations on which each median was based. In addition to providing more stable estimates of the median, this collapsing seemed to be justified because the child had no knowledge concerning the set to be tested on probe trials. The pause time analysis included age (3), sex (2), serial position (8), and trial type (forget and probe), with repeated measures on the last two variables. Control and precued trials were excluded from this analysis since they had only four serial positions. They were included, however, in a subsequent analysis. The means for each age group and trial type are shown in Fig. 1. There were significant main effects due to age, F(2, 42) = 6.65, p < .Ol and serial position, F(7, 294) = 3.76, p < .Ol. The means for the 7-, 9-, and 11-year-old groups were .86, .93, and 1.23 set, respectively. As can be seen in Fig. 1, the main effect due to serial position was due to a tendency for the pause time to be the longest at the fifth and the shortest at the last serial position. The main effects due to sex and trial type did not approach significance (F < 1 in both cases).
SEflIRL FIG.
children
I.
PLlSlTlON
Mean median pause time as a function (Experiment I) and for adults (Experiment
of serial 2).
position
for each age group
of
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The only significant interactions were trial type x serial position, F(7. 294) = 2.56, p < .05 and sex x serial position, F(7, 294) = 2.40, p < .05. In the trial type by serial position interaction, pause time was about the same for both the forget and probe trials at all serial positions except the last, where it was shorter on probe trials. In the sex x serial position interaction pause time was about the same for both boys and girls at all serial positions except the first two and the last serial position. On the first two positions the girls paused for a shorter time and on the last the boys paused for a shorter time. In spite of the main effects due to serial position and the two “weak” interactions with serial position, the most striking feature of these data was the relatively flat pause time patterns. No difference was greater than about .15 sec. It is possible that these raw pause times might not reflect subtle differences in allocation of study time. In order to investigate this possibility, the analysis was repeated using normalized pause times. The mean and standard deviation for each individual on each trial type was computed and then each study time converted to a z score. The mean z scores for serial Positions 1-8 were .02, .02, -.Ol, -.Ol, .22, -.08, -.Ol, and - .17, respectively. As in the analysis of raw pause times the main effect of serial position was significant, F(7, 294) = 4.03, p < .Ol. Like the raw pause times, the normalized pattern was extremely flat. Also consistent with the analysis of raw pause time, the age x serial position interaction was not significant (F < 0). Further, all other interactions involving serial position were not significant. To further investigate the pause time patterns, the data from the control, precued, forget, and probe trials were subjected to supplementary analyses. Pause times for control trials were compared to pause times on the first four serial positions of the forget and probe trials. No differences among these trial types were found at any age. In another analysis the precued trials were compared to the last four serial positions of the forget and probe trials. There were no differences among these trial types. Discussion The data from Experiment 1 present a very interesting picture of developmental changes in the ability to deal with irrelevant information in immediate memory. For the youngest children, interference from the to-be-forgotten material was not eliminated as indicated by the finding that recall on both precued and control trials was higher than on forget and Probe 2 trials. For the 9-year-old children the cue to forget facilitated recall (forget > Probe 2) but not all interference was eliminated because recall was higher on precued than on forget trials. The 1I-year-olds, however, used a forget cue to facilitate recall and to eliminate interference from the to-be-forgotten items as indicated by the finding that recall on
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forget, precued, and control trials was higher than on Probe 2 trials. Because a prerequisite for inclusion in the experiment was comprehension of the meaning of the forget cue, these findings cannot be attributed to developmental changes in comprehension of the forget cue. Rather, they reflect a developmental change in the use of the forget cue. While there were clear developmental changes in the patterns of recall accuracy, the changes in pause time patterns across the three age groups were minimal. All the children moved quickly through the sequence of pictures pausing briefly (x = .99 set) between stimuli. The 7-year-olds did not pause as long as the 1 I-year-olds, but the differences (although statistically significant) were relatively small as compared to those obtained in previous studies using the pause time measure. Inferences drawn from data similar to those obtained herein have always been that flat pause time patterns indicate no cumulative rehearsal (Belmont & Butterfield, 1971a, 1971b, 1977; Bray, 1979; Bray, Goodman, &Justice, 1982; Butterfield & Belmont, 1971). Thus, the effective directed forgetting performance of the 1 I-year-olds did not appear to be the result of the selective rehearsal strategy hypothesized to be adopted by adults in this task. EXPERIMENT
2
In this experiment adults were given the same directed forgetting task as used with children in Experiment 1. Previous experiments with adults have relied on rather indirect strategy measures. Evidence for the use of selective rehearsal has been based on subject-reports (Bjork, 1970; Reitman, Malin, Bjork, & Higman, 1973), on the presence of primacy effects for the to-be-remembered items (Block, 1971; Bruce & Papay, 1970), and on lowered performance on a distractor task with instructions to remember as compared to instructions to forget (Roediger & Crowder, 1972). The pause time measure used in the present experiment thus provided the most direct test, to date, of Bjork’s (1972) selective rehearsal hypothesis. Method Subjects. The participants were 16 college students enrolled in an introductory psychology course at the University of Cincinnati. There were eight males and eight females. Stimulus materials and upparutus. These were the same as in Experiment 1. Procedure. All adults were tested individually in a quiet room on the University campus. The testing suite was divided into two rooms so that the control equipment was isolated from the participant. As in Experiment 1, the pretraining and experimental sessions were separated by about 48 hr. The only changes in procedure were (a) those made so that instructions were age appropriate: and (b) those required
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by the use of five pictures on control and precued trials and 10 pictures on Probe I, Probe 2, and forget trials.’ All other aspects of the procedure were the same as in Experiment 1. Results
Accuvac?, ana/~~sis. The analysis of variance of proportion correctly recalled included sex (2), trial type (5), and serial position (5). where the latter two variables were within-subjects variables. The only significant effects were due to trial type, F(4, 56) = 26.45, p < .Ol and serial position, F(4, 56) = 17.06, p < .Ol. The means for the five trial types are shown in Table I. Newman-Keuls (a = .05) indicated (forget = precued = control) > Probe 2 > Probe I. The means for serial Positions l-5 were .84, .78, .70, .65. and .63, respectively. Pause time analysis. As in Experiment 1, the Probe I and Probe 2 trials were combined into one trial type (probe). The analysis of variance included sex (2). trial type (forget and probe), and serial position (IO). There were significant main effects due to trial type, F(l, 14) = 14.52, p < .Ol and serial position, F(9, 126) = 9.32, p < .Ol. The means for the forget and the probe trials were 1.74 and 2.05 set, respectively. The means for serial Positions I-10 were, in order: 1.27, 1.66, 1.93, 1.99, 2.60, 2.19, 1.69, 1.79, 2.04, and 1.78. The only other significant effect was the interaction of trial type and serial position, F(9. 126) = 6.56, p < .Ol. The means for this interaction are shown in Fig. 1. Pause time increased steadily across the first five serial positions for both trial types. Following a forget cue after the fifth picture, pause time returned to the initial level and then increased across the remaining serial positions. On probe trials, pause time increased at serial Position 6 rather than decreased. For Positions 7-10, pause time decreased to an average of about 2 set per item. The pause times from the control and precue trials were analyzed in separate analyses. Control and precued pause times were also not significantly different from those on the first five serial positions of either forget or probe trials. Discussion
The present results are consistent with other studies on directed forgetting with adults (e.g., Bjork. 1972; Epstein, 1972). The forget cue facilitated recall and interference from the to-be-forgotten items was eliminated. This pattern of results, including the level of recall accuracy, was comparable to that obtained with 1l-year-old children in Experiment I. ’ Pilot testing indicated that if the number of to-be-remembered of four as used with the children) recall in adults would be more of recall of the I l-year-old children in Experiment I.
items was five (instead comparable to the level
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The pause time measure provided striking evidence for the use of selective rehearsal. Pause time on the first item following a forget cue was virtually identical to the pause time for the first item in the sequence, indicating that the participants were starting a new “rehearsal scheme” (Bjork, 1972). Pause time then began to increase again across the remaining serial positions. These data reflected a selective rehearsal strategy with exactly the characteristics specified by the Bjork (1972) model. The data from these two experiments indicate that there are not only developmental changes from ineffective to effective directed forgetting strategies, but there is a difference in the nature of effective directed forgetting strategies used by 11-year-old children and those used by adults. GENERAL DISCUSSION The development of the ability to disregard irrelevant information in memory appears to have two transition periods. The first is a transition from ineffective to effective directed forgetting. Seven-year-old children did not utilize a cue to forget and nine-year-old children were only partially successful at doing so. By eleven years of age, however, the children had no difficulty disregarding irrelevant information in memory. During the second transition, directed forgetting is effective but there is a transition from no rehearsal to the use of a selective rehearsal strategy. This second transition period apparently occurs between 1 I years of age and adulthood. Although the 11-year-olds effectively disregarded irrelevant information in memory, they did not use a selective rehearsal strategy. Adults, in contrast, used a sophisticated rehearsal strategy as described by Bjork (1972). Thus, there is a qualitative difference in the type of effective directed forgetting strategy used by children at 1I years of age and that used by adults. Brown (1974) noted that on most tasks, the spontaneous use of memory strategies quickly progresses from no production to production with no well-defined intermediate steps. The present data provide a striking exception to this pattern. Bray (1979) suggested that it may be possible to adopt an effective directed forgetting strategy without using selective rehearsal. This explanation was based on the recency discrimination hypothesis of Bjork and Whitten (1974) which stresses the discriminability of items from each other in terms of time. If a person understands the significance of the forget cue. the to-be-forgotten items are differentiated from the to-be-remembered items on the basis of the “anchor” provided by the color change and by recency information. It should be noted that this is not an “automatic process” (Shiffrin & Schneider. 1977). The person must understand the significance of the forget cue and UYCit to aid selective retrieval. (Bray, 1979. p. 714)
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This selective retrieval strategy is similar to one described by Epstein (1972) and is given some credence by the demonstration of excellent recency discrimination abilities in young children (Brown, 1972, 1973). There is a need for additional research to provide a clearer definition of the nature of developmental changes from the use of a selective retrieval strategy based on recency discrimination in preadolescence to the use of selective rehearsal in adulthood. These additional investigations will provide us with a clearer understanding of developmental changes in the ability to disregard irrelevant information in memory. REFERENCES Belmont. J. M., & Butterfield, E. C. Learning strategies as determinants of memory deficiencies. Cognirirr Psychology. 1971. 2, 41 l-420. (a) Belmont, J. M.. & Butterfield, E. C. What the development of short-term memory is. Human Development. 1971. 14, 236-248. (b) Belmont. J. M., & Butterfield, E. C. The instructional approach to developmental cognitive research. In R. Kail & J. Hagen (Eds.). Perspectives on the development of memory and cog&ion. Hillsdale, N.J.: Erlbaum. 1977. Bjork. R. A. Positive forgetting: The non-interference of items intentionally forgotten. Journal
of Verbal
Learning
and
Verbal
Behavior.
1970, 9, 255-268.
Bjork, R. A. Theoretical implications of directed forgetting. In A. W. Melton & E. Martin tEds.1. Coding processes in hrrmun memory. Washington. D.C.: Winston, 1972. Bjork. R. A., & Whitten, W. B. Recency-sensitive retrieval processes in long-term free recall. CognifiLse Psychology, 1974, 6, 173-189. Block, R. A. Effects of instructions to forget in short-term memory. Journal of Experimental Psychology.
1971. 89, l-9.
Bray, N. W. Strategy production in the retarded. In N. R. Ellis (Ed.), Handbook of mental dqficiency: Psychological theoy rend research. Hillsdale. N.J.: Erlbaum. 1979. 2nd ed. Bray, N. W., & Ferguson. R. P. Memory strategies used by young normal and retarded children in a directed forgetting paradigm. Journal yfExperimenra/ Child Psychology. 1976, 22, 200-215.
Bray. N. W., Goodman, M. A., & Justice. E. M. Task instructions and strategy transfer in the directed forgetting performance of mentally retarded adolescents. Intelligence. 1982. 6, 187-200.
Brown, A. L. Context and recency cues in the recognition memory of retarded children and adolescents. American Journal of Mental Dejiciency. 1972. 77. 54-58. Brown. A. L. Temporal and contextual cues as discriminative attributes in retardates’ recognition memory. Journal of Experimental Psych&g?. 1973, 98, l-13. Brown, A. L. The role of strategic behavior in retardate memory. In N. R. Ellis (Ed.), Inrernational reliew, of research in mental retardation (Vol. 7). New York: Academic Press, 1974. Bruce, D.. & Papay, J. P. Primary effect in single-trial free recall. Journal of Verbal Learning
und
Verbal
Behavior.
1970. 9, 473-486.
Butterfield, E. C.. & Belmont, J. M. Relations of storage and retrieval strategies as shortterm memory processes. Journal of Experimental Psychology. 1971, 89, 319-328. Epstein, W. Mechanisms of directed forgetting. In G. H. Bower (Ed.). The psychology of learning and motiwrion (Vol. 6). New York: Academic Press. 1972. Gibson, E. J. Principles of percepturrl learning and del*elopment. New York: AppletonCentury-Crofts. 1969. Hagen. J. W.. & Stanovich. K. G. Memory: Strategies of acquisition. In R. V. Kail &
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J. W. Hagen (Eds.), Perspectives on the development of memor?, and cognition. Hillsdale, N.J.: Erlbaum, 1977. Howard, D., & Goldin, S. Selective processing in encoding and memory: An analysis of resource allocation in kindergarten children. Journal of Experimental Child Psychology, 1979, 27, 87-95. MacLeod, C. M. Long-term recognition and recall following directed forgetting. Journul of Experimental Psychology: Human Learning and Memory, 1975. 104, 271-279. Reitman. W. R., Malin, J. T.. Bjork, R. A., & Higman. B. Strategy control and directed forgetting. Journnl of Verbal Learning and Verbal Behavior, 1973, 12, 140-149. Roediger, H. L. III. & Crowder, R. Cl. Instructed forgetting: Rehearsal control or retrieval inhibition (Repression)? Cognitive Psychology, 1972. 3, 244-254. Shiffrin, R. M., & Schneider, W. Controlled and automatic human information processing: II. Perceptual learning, automatic attending, and a general theory. Psycholug&/ Review, 1977, 84, 127-190. Wright, J. C., & Vlietstra, A. G. The development of selective attention: From perceptual exploration to logical search. In H. W. Reese (Ed.), Advances in child development and behavior (Vol. IO). New York: Academic Press, 1975.
RECEIVED: November 2, 1981: REVISED:August 2. 1982.
OF EXPERIMENTAL
CHILD
PSYCHOLOGY
36, 43-55 (1983)
Two Developmental Transitions in Selective Remembering Strategies NORMAN W. BRAY The University of Alabama
ELAINE M. JUSTICE Old Dominion University AND DAVID N. ZAHM University of Cincinnati Two experiments were reported investigating developmental changes in the use of strategies to eliminate interference from irrelevant information in memory. The participants in the first were 7-. 9-, and 1 l-year-old children and those in the second were adults. In both experiments a directed forgetting paradigm was used in which the person was presented two sets of pictures but only recalled one set on a trial. On some trials there was a cue to forget the first set and to remember only the second set. There were two developmental transitions. The first was from ineffective to effective selective remembering which occurred between 7 and 11 years of age. The second, which occurred between 11 years of age and adulthood, was from the use of selective retrieval strategy to a more sophisticated rehearsal strategy. The implications of these two developmental transitions were discussed.
An important part of cognitive development is the increasing ability of the child to respond to task-relevant stimuli and to disregard irrelevant stimuli (Gibson, 1969; Hagen & Stanovich, 1977; Wright & Vlietstra, The cooperation of the principal, faculty, and students of Houston Elementary School is gratefully acknowledged. The first experiment reported was completed in partial fulfillment of the Master of Arts Degree by David Zahm in the Department of Psychology, University of Cincinnati, under the supervision of Norman Bray. This research was supported by NIH Research Grant HD 15669 from the National Institute of Child Health and Human Development, first author Principal Investigator. Requests for reprints should be sent to Norman W. Bray, Department of Psychology, Box 2968, The University of Alabama. University, AL 35486. 43 0022-0965183 $3.00 Copyright 0 1983 by Academic Press. Inc. All rights of reproduction in any form reserved.
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1975). One aspect of selectivity which has received relatively little research attention is the ability to select relevant information and to disregard irrelevant information already stored in memory (Bray, 1979). The ability to disregard information in memory has usually been studied in a directed forgetting paradigm in which the person is occasionally given a cue to forget information previously presented. In order to assure that the person tries to remember all the information until a cue to forget is given, frequent control trials with no forget cue are included. Effective directed forgetting is indicated when the functional memory load is determined by the number of to-be-remembered items and is independent of the number of to-be-forgotten items. Numerous studies have found that adults spontaneously adopt strategies that eliminate interference from irrelevant information (see Bjork, 1972; Epstein, 1972; MacLeod, 1975 for reviews). Bjork (1972) found that effective directed forgetting depends on two interrelated factors: (a) the use of selective rehearsal and (b) differentiation of the to-be-forgotten and to-be-remembered items in memory. In selective rehearsal all items are rehearsed until a cue to forget is given, but following a cue, rehearsal of the to-be-forgotten items is terminated and all further processing is devoted to the subsequent to-be-remembered items. Differentiation refers to the functional separation of to-be-forgotten and to-be-remembered items which may occur as a result of selective rehearsal. Although there have been no developmental studies of directed forgetting, the results of two studies with young children indicate that marked developmental changes can be expected. Howard and Goldin (1979) used a version of the directed forgetting paradigm in which some kindergarten children were given a precue concerning the information to be forgotten. Others were given a regular directed forgetting task in which the cue occurred following the presentation of the to-be-forgotten items. With the precue, kindergarten children had no difficulty disregarding the irrelevant information. Without the precue the irrelevant information interfered with recall of the to-be-remembered items. Bray and Ferguson (1976) tested first-grade children in a directed forgetting task in which the forget cue occurred within a sequence on some trials. There were frequent control trials with no forget cue. First-grade children processed the items following a forget cue more actively than the items before a forget cue. Bray and Ferguson noted that this strategy was considerably less sophisticated than the one described by Bjork (1972) and presumably used by adults. The studies with children (Bray & Ferguson, 1976; Howard & Goldin, 1979) and those with adults (Bjork, 1972) present an interesting (but incomplete) picture of developmental changes in the ability to disregard irrelevant information in memory. Kindergarten children can disregard information if given a cue before the information is presented. but not once the items have been processed. First-grade children adopt relatively
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unsophisticated strategies and adults use strategies that minimize interference from the to-be-forgotten material. Two experiments are reported here which were designed to provide a clearer understanding of developmental changes in directed forgetting performance and changes in the nature of the strategies used. The task consisted of five trial types in which the participant was requested to remember a set of picture names. On forget trials four pictures on a yellow background and then four pictures on a blue background were presented, but only the blue pictures were tested. Thus the color change was a signal to forget the previously presented yellow pictures. On Probe 1 and Probe 2 trials, eight yellow pictures were presented for study. The first four were tested for recall on Probe 1 trials and the last four on Probe 2 trials. On precued and control trials only four pictures were presented. On precued trials the participant was given a cue that only four pictures would be presented and then tested. On control trials there was no precue. ’ Effective directed forgetting would be indicated if two results were obtained. First, recall accuracy should be higher on forget than on Probe 2 trials, indicating a facilitation due to the forget instruction. Second, recall accuracy on forget, precued, and control trials should not differ, indicating that the facilitation provided by the forget instruction was due to the elimination of interference from the to-be-forgotten material. Because Bjork (1972) suggested that rehearsal was an important aspect of an effective directed forgetting strategy, the pause time procedure of Belmont and Butterfield (1971a, 1971b) was used to monitor the type of acquisition strategy. If selective rehearsal is used, the length of pauses between items should increase as pictures are presented. Following a forget cue the pause time should be “reset” to its original level and then increase again as the subsequent pictures are presented. In the first experiment, developmental changes in directed forgetting performance (accuracy) and the nature of the directed forgetting strategy (pause time) were examined in 7-, 9-, and 11-year-old children. In the second, the same aspects of directed forgetting were examined in adults. EXPERIMENT
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Method Subjects. The participants were 48 children, 16 each from the first-, third-, and fifth-grade classrooms in two different schools in Cincinnati, Ohio. There was an equal number of boys and girls in each age group with mean ages of 7.0 (SD = .3), 9.2 (SD = .4), and 11.0 (SD = .2). All students were in their age appropriate grade placements. ’ As explained in detail in the method section, the color backgrounds were counterbalanced so that the initial color (yellow or blue) could not be used to determine the trial type.
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Stimulus materials. The stimuli were twenty-two 2 x 2-in. (5.08 x 5.0%cm) slides of black on white line drawings of common objects such as ball, chair, table, and hat. Each stimulus was photographed on 35mm transparency film. These stimuli were similar to those used in previous studies of directed forgetting in children (e.g., Bray, 1979). Apparatus. The main components of the apparatus was a lo-window rear projection device (Model MPRO-310, Behavior Apparatus Builders). The windows measuring 1.75 x 2.00 in. (4.45 x 5.08 cm) were arranged in a single row at the front of the projection device. The front was covered with a black mat board facing with openings for Windows 1-8. A strip of .50-in. (1.27-cm) white tape divided the display into two sets of four windows each. Below each window was a button which the child pressed to expose a stimulus. Each window could be illuminated individually by either a projection lamp, which displayed a picture, or by a probe lamp, which illuminated the window without projecting a picture. An eight-channel paper tape reader (Model TPI UR, Behavior Apparatus Builders) was used to control the projection device. A printing clock counter was used for recording interitem pause times (Model PR210A. Behavior Apparatus Builders). Procedure. All children were tested individually in a mobile laboratory parked on the school grounds. This laboratory was divided into two rooms so that the control equipment was isolated from the child. There was one pretraining session and one experimental session separated by about 48 hr. In order to assure that the pictures could be identified, each child was required to name the pictures prior to beginning the pretraining. None of the children had difficulty with this task. Following the stimulus familiarization, the child was trained on the pause time procedure. This consisted of six trials in which the number of pictures was gradually increased from two to four. The sequence of events was as follows: The child pressed the button below the first window and the stimulus was projected in the window for 1 set; there was a subject-determined pause; the second button was pressed: the second picture appeared. This procedure was repeated for the remaining pictures on a trial. There was a I-set retention interval following the last button press: for 10 set a probe lamp illuminated the window of the picture to be recalled. Successive pictures were tested, in order, in this manner, beginning with Picture I on Control 1 and Probe 1 trials and Picture 5 on Forget, Precued, and Probe 2 trials. This was followed by an experimenter-paced intertrial interval. If the child gave a picture name (correct or incorrect) during the IO-set recall interval for a given probe, the experimenter immediately advanced the apparatus to the next probe. Over the next five trials the number of study items was gradually increased from four to six to eight. On these trials the child was tested on either the first half (Probe 1) or the second half (Probe 2) of the items presented. For instance, if four pictures were presented, either the first
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two or the last two were tested. The children were instructed to try to remember all the pictures since they were not told which set would be tested on a particular trial. On the Probe 1 and Probe 2 trials all of the pictures had either a blue or yellow background. The signal to forget procedure was then introduced. The children were instructed that when the background color changed (yellow-blue or blueyellow), only the second color pictures would be tested. This meant that they could forget the items presented before a color change. It was also stressed that since there were trials with no color change, they should try to remember all items until a color change occurred. Following the forget trials, control and precued trials were introduced. On control trials four pictures were presented in Windows l-4 and tested. On precued trials the equipment did not operate when the child pressed the first button. This was a cue to press the fifth button. The four pictures for that trial were then viewed in Windows 5-8. The first button was operative for all other trial types. At the beginning of the experimental session there was a review of the trial types, two warm-up trials consisting of one Probe 1 trial and one precued trial, and a comprehension test. In the comprehension test, the children were asked to explain what to do when they saw pictures on a yellow background in the first four windows and pictures with a blue background in the last four windows. Likewise they were asked what it meant and what to do when they saw pictures with all the same background color. All but one child answered the comprehension test questions correctly. The one child who failed this comprehension test (a 7-year-old) was excluded and replaced. Following the comprehension test there were 24 experimental trials which included six forget trials, five trials each for the control and precued trials, and four trials each on Probe 1 and Probe 2 trial types. Four different presentation orders were used to balance the presentation order of the trial types and to assure that each picture was used in each trial type approximately equally often. Results Accuracy analysis. A response was scored as correct when the picture recalled was the same as the picture which appeared in the window probed. The proportion of correct responses was computed for each child at each serial position by collapsing over trials on each of the five trial types.’ All post hoc tests were conducted with the Newman-Keuls procedure (CI = .05). ’ For each of the analyses of variance on proportion correct responses reported in this paper, identical analyses were performed on an arc sine transformation. Because the pattern of results in both sets of analyses was the same in all cases. only the analyses on proportion correct are reported.
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The analysis of variance included age (7, 9, and I I years old), sex (2), trial type (forget, control, precued, Probe 1, and Probe 2), and serial position (one through four), where the latter two factors were withinsubjects variables. There were significant main effects for age. F(2, 42) = 8.83, p < .Ol; trial type, F(4, 168) = 4.55, p < .Ol; and serial position, F(3, 126) = 3.58, p < .Ol. The means for the 7-, 9-, and 11-year-olds were .26, .44, SO, respectively. Post hoc tests indicated equivalent recall for 9- and 1 l-year-old children with both groups higher than the 7-yearolds. For the precued, control, forget, Probe 2, and Probe 1 conditions the means were, in order: .57, .49, .48, .29, and .20. Newman-Keuls tests indicated the following pattern of differences: precued > (forget = control) > Probe 2 > Probe 1. The means for serial Positions l-4 were .56, .45, .35, and .30, respectively. All serial positions were significantly different from each other. There was a significant interaction between trial type and age, F(8, 168) = 4.63, p < .Ol. The means for this interaction are shown in Table 1. There was no facilitation due to the forget cue in the 7-year-olds with accuracy on forget trials equal to accuracy on Probe 2 trials. Recall accuracy on control trials was equal to accuracy for precued trials. Accuracy for control and precued trials was greater than recall accuracy on both probe trials. The 9-year-old children demonstrated some facilitation due to the forget cue. Accuracy on forget trials was equal to that on control trials and greater than accuracy on Probe 2 trials. However, performance on precued trials was significantly better than recall on forget trials. The 1 I-year-olds demonstrated more effective performance on the directed forgetting task. The cue clearly facilitated performance. Recall was greater on forget trials than on Probe 2 trials and equal to that obtained on both control and precued trials. The pattern of differences for the 1 l-year-old children was as follows: (forget = control = precued) > (Probe 2 = Probe 1). There was also a significant interaction between serial position and age, F(6, 126) = 2.44, p < .05. All three age groups showed marked TABLE MEAN
PROPORTION
1
CORRECTLY
RECALLED
Age group Trial type Forget Premed Control Probe I Probe 2
7 years
9 years
11 years
Adults
.27 .33 .34 .16 .20
.51 .65 .51 .18 .35
.66 .72 .62 .26 .32
.83 .83 .85 .49 .60
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primacy effects. However, 9-year-old children demonstrated a more distinct recency effect than the other groups. The only other significant interaction was between trial type and serial position, F(12, 504) = 4.18, p < .Ol. Recall on forget, control, and precued trials was not significantly different at the first two serial positions. At the last two serial positions, however, recall accuracy was greater on precued than on either forget or control trials. Across serial positions, recall on Probe 1 and Probe 2 trials was consistently less than accuracy on the other trial types. Pause time analyses. The pause time measure was the median pause time for each child at each serial position. For the purposes of this analysis the median pause time for the Probe trials was based on the combined Probe 1 and Probe 2 pause times, thus increasing the number of observations on which each median was based. In addition to providing more stable estimates of the median, this collapsing seemed to be justified because the child had no knowledge concerning the set to be tested on probe trials. The pause time analysis included age (3), sex (2), serial position (8), and trial type (forget and probe), with repeated measures on the last two variables. Control and precued trials were excluded from this analysis since they had only four serial positions. They were included, however, in a subsequent analysis. The means for each age group and trial type are shown in Fig. 1. There were significant main effects due to age, F(2, 42) = 6.65, p < .Ol and serial position, F(7, 294) = 3.76, p < .Ol. The means for the 7-, 9-, and 11-year-old groups were .86, .93, and 1.23 set, respectively. As can be seen in Fig. 1, the main effect due to serial position was due to a tendency for the pause time to be the longest at the fifth and the shortest at the last serial position. The main effects due to sex and trial type did not approach significance (F < 1 in both cases).
SEflIRL FIG.
children
I.
PLlSlTlON
Mean median pause time as a function (Experiment I) and for adults (Experiment
of serial 2).
position
for each age group
of
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The only significant interactions were trial type x serial position, F(7. 294) = 2.56, p < .05 and sex x serial position, F(7, 294) = 2.40, p < .05. In the trial type by serial position interaction, pause time was about the same for both the forget and probe trials at all serial positions except the last, where it was shorter on probe trials. In the sex x serial position interaction pause time was about the same for both boys and girls at all serial positions except the first two and the last serial position. On the first two positions the girls paused for a shorter time and on the last the boys paused for a shorter time. In spite of the main effects due to serial position and the two “weak” interactions with serial position, the most striking feature of these data was the relatively flat pause time patterns. No difference was greater than about .15 sec. It is possible that these raw pause times might not reflect subtle differences in allocation of study time. In order to investigate this possibility, the analysis was repeated using normalized pause times. The mean and standard deviation for each individual on each trial type was computed and then each study time converted to a z score. The mean z scores for serial Positions 1-8 were .02, .02, -.Ol, -.Ol, .22, -.08, -.Ol, and - .17, respectively. As in the analysis of raw pause times the main effect of serial position was significant, F(7, 294) = 4.03, p < .Ol. Like the raw pause times, the normalized pattern was extremely flat. Also consistent with the analysis of raw pause time, the age x serial position interaction was not significant (F < 0). Further, all other interactions involving serial position were not significant. To further investigate the pause time patterns, the data from the control, precued, forget, and probe trials were subjected to supplementary analyses. Pause times for control trials were compared to pause times on the first four serial positions of the forget and probe trials. No differences among these trial types were found at any age. In another analysis the precued trials were compared to the last four serial positions of the forget and probe trials. There were no differences among these trial types. Discussion The data from Experiment 1 present a very interesting picture of developmental changes in the ability to deal with irrelevant information in immediate memory. For the youngest children, interference from the to-be-forgotten material was not eliminated as indicated by the finding that recall on both precued and control trials was higher than on forget and Probe 2 trials. For the 9-year-old children the cue to forget facilitated recall (forget > Probe 2) but not all interference was eliminated because recall was higher on precued than on forget trials. The 1I-year-olds, however, used a forget cue to facilitate recall and to eliminate interference from the to-be-forgotten items as indicated by the finding that recall on
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forget, precued, and control trials was higher than on Probe 2 trials. Because a prerequisite for inclusion in the experiment was comprehension of the meaning of the forget cue, these findings cannot be attributed to developmental changes in comprehension of the forget cue. Rather, they reflect a developmental change in the use of the forget cue. While there were clear developmental changes in the patterns of recall accuracy, the changes in pause time patterns across the three age groups were minimal. All the children moved quickly through the sequence of pictures pausing briefly (x = .99 set) between stimuli. The 7-year-olds did not pause as long as the 1 I-year-olds, but the differences (although statistically significant) were relatively small as compared to those obtained in previous studies using the pause time measure. Inferences drawn from data similar to those obtained herein have always been that flat pause time patterns indicate no cumulative rehearsal (Belmont & Butterfield, 1971a, 1971b, 1977; Bray, 1979; Bray, Goodman, &Justice, 1982; Butterfield & Belmont, 1971). Thus, the effective directed forgetting performance of the 1 I-year-olds did not appear to be the result of the selective rehearsal strategy hypothesized to be adopted by adults in this task. EXPERIMENT
2
In this experiment adults were given the same directed forgetting task as used with children in Experiment 1. Previous experiments with adults have relied on rather indirect strategy measures. Evidence for the use of selective rehearsal has been based on subject-reports (Bjork, 1970; Reitman, Malin, Bjork, & Higman, 1973), on the presence of primacy effects for the to-be-remembered items (Block, 1971; Bruce & Papay, 1970), and on lowered performance on a distractor task with instructions to remember as compared to instructions to forget (Roediger & Crowder, 1972). The pause time measure used in the present experiment thus provided the most direct test, to date, of Bjork’s (1972) selective rehearsal hypothesis. Method Subjects. The participants were 16 college students enrolled in an introductory psychology course at the University of Cincinnati. There were eight males and eight females. Stimulus materials and upparutus. These were the same as in Experiment 1. Procedure. All adults were tested individually in a quiet room on the University campus. The testing suite was divided into two rooms so that the control equipment was isolated from the participant. As in Experiment 1, the pretraining and experimental sessions were separated by about 48 hr. The only changes in procedure were (a) those made so that instructions were age appropriate: and (b) those required
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by the use of five pictures on control and precued trials and 10 pictures on Probe I, Probe 2, and forget trials.’ All other aspects of the procedure were the same as in Experiment 1. Results
Accuvac?, ana/~~sis. The analysis of variance of proportion correctly recalled included sex (2), trial type (5), and serial position (5). where the latter two variables were within-subjects variables. The only significant effects were due to trial type, F(4, 56) = 26.45, p < .Ol and serial position, F(4, 56) = 17.06, p < .Ol. The means for the five trial types are shown in Table I. Newman-Keuls (a = .05) indicated (forget = precued = control) > Probe 2 > Probe I. The means for serial Positions l-5 were .84, .78, .70, .65. and .63, respectively. Pause time analysis. As in Experiment 1, the Probe I and Probe 2 trials were combined into one trial type (probe). The analysis of variance included sex (2). trial type (forget and probe), and serial position (IO). There were significant main effects due to trial type, F(l, 14) = 14.52, p < .Ol and serial position, F(9, 126) = 9.32, p < .Ol. The means for the forget and the probe trials were 1.74 and 2.05 set, respectively. The means for serial Positions I-10 were, in order: 1.27, 1.66, 1.93, 1.99, 2.60, 2.19, 1.69, 1.79, 2.04, and 1.78. The only other significant effect was the interaction of trial type and serial position, F(9. 126) = 6.56, p < .Ol. The means for this interaction are shown in Fig. 1. Pause time increased steadily across the first five serial positions for both trial types. Following a forget cue after the fifth picture, pause time returned to the initial level and then increased across the remaining serial positions. On probe trials, pause time increased at serial Position 6 rather than decreased. For Positions 7-10, pause time decreased to an average of about 2 set per item. The pause times from the control and precue trials were analyzed in separate analyses. Control and precued pause times were also not significantly different from those on the first five serial positions of either forget or probe trials. Discussion
The present results are consistent with other studies on directed forgetting with adults (e.g., Bjork. 1972; Epstein, 1972). The forget cue facilitated recall and interference from the to-be-forgotten items was eliminated. This pattern of results, including the level of recall accuracy, was comparable to that obtained with 1l-year-old children in Experiment I. ’ Pilot testing indicated that if the number of to-be-remembered of four as used with the children) recall in adults would be more of recall of the I l-year-old children in Experiment I.
items was five (instead comparable to the level
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The pause time measure provided striking evidence for the use of selective rehearsal. Pause time on the first item following a forget cue was virtually identical to the pause time for the first item in the sequence, indicating that the participants were starting a new “rehearsal scheme” (Bjork, 1972). Pause time then began to increase again across the remaining serial positions. These data reflected a selective rehearsal strategy with exactly the characteristics specified by the Bjork (1972) model. The data from these two experiments indicate that there are not only developmental changes from ineffective to effective directed forgetting strategies, but there is a difference in the nature of effective directed forgetting strategies used by 11-year-old children and those used by adults. GENERAL DISCUSSION The development of the ability to disregard irrelevant information in memory appears to have two transition periods. The first is a transition from ineffective to effective directed forgetting. Seven-year-old children did not utilize a cue to forget and nine-year-old children were only partially successful at doing so. By eleven years of age, however, the children had no difficulty disregarding irrelevant information in memory. During the second transition, directed forgetting is effective but there is a transition from no rehearsal to the use of a selective rehearsal strategy. This second transition period apparently occurs between 1 I years of age and adulthood. Although the 11-year-olds effectively disregarded irrelevant information in memory, they did not use a selective rehearsal strategy. Adults, in contrast, used a sophisticated rehearsal strategy as described by Bjork (1972). Thus, there is a qualitative difference in the type of effective directed forgetting strategy used by children at 1I years of age and that used by adults. Brown (1974) noted that on most tasks, the spontaneous use of memory strategies quickly progresses from no production to production with no well-defined intermediate steps. The present data provide a striking exception to this pattern. Bray (1979) suggested that it may be possible to adopt an effective directed forgetting strategy without using selective rehearsal. This explanation was based on the recency discrimination hypothesis of Bjork and Whitten (1974) which stresses the discriminability of items from each other in terms of time. If a person understands the significance of the forget cue. the to-be-forgotten items are differentiated from the to-be-remembered items on the basis of the “anchor” provided by the color change and by recency information. It should be noted that this is not an “automatic process” (Shiffrin & Schneider. 1977). The person must understand the significance of the forget cue and UYCit to aid selective retrieval. (Bray, 1979. p. 714)
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This selective retrieval strategy is similar to one described by Epstein (1972) and is given some credence by the demonstration of excellent recency discrimination abilities in young children (Brown, 1972, 1973). There is a need for additional research to provide a clearer definition of the nature of developmental changes from the use of a selective retrieval strategy based on recency discrimination in preadolescence to the use of selective rehearsal in adulthood. These additional investigations will provide us with a clearer understanding of developmental changes in the ability to disregard irrelevant information in memory. REFERENCES Belmont. J. M., & Butterfield, E. C. Learning strategies as determinants of memory deficiencies. Cognirirr Psychology. 1971. 2, 41 l-420. (a) Belmont, J. M.. & Butterfield, E. C. What the development of short-term memory is. Human Development. 1971. 14, 236-248. (b) Belmont. J. M., & Butterfield, E. C. The instructional approach to developmental cognitive research. In R. Kail & J. Hagen (Eds.). Perspectives on the development of memory and cog&ion. Hillsdale, N.J.: Erlbaum. 1977. Bjork. R. A. Positive forgetting: The non-interference of items intentionally forgotten. Journal
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Bjork, R. A. Theoretical implications of directed forgetting. In A. W. Melton & E. Martin tEds.1. Coding processes in hrrmun memory. Washington. D.C.: Winston, 1972. Bjork. R. A., & Whitten, W. B. Recency-sensitive retrieval processes in long-term free recall. CognifiLse Psychology, 1974, 6, 173-189. Block, R. A. Effects of instructions to forget in short-term memory. Journal of Experimental Psychology.
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Bray, N. W. Strategy production in the retarded. In N. R. Ellis (Ed.), Handbook of mental dqficiency: Psychological theoy rend research. Hillsdale. N.J.: Erlbaum. 1979. 2nd ed. Bray, N. W., & Ferguson. R. P. Memory strategies used by young normal and retarded children in a directed forgetting paradigm. Journal yfExperimenra/ Child Psychology. 1976, 22, 200-215.
Bray. N. W., Goodman, M. A., & Justice. E. M. Task instructions and strategy transfer in the directed forgetting performance of mentally retarded adolescents. Intelligence. 1982. 6, 187-200.
Brown, A. L. Context and recency cues in the recognition memory of retarded children and adolescents. American Journal of Mental Dejiciency. 1972. 77. 54-58. Brown. A. L. Temporal and contextual cues as discriminative attributes in retardates’ recognition memory. Journal of Experimental Psych&g?. 1973, 98, l-13. Brown, A. L. The role of strategic behavior in retardate memory. In N. R. Ellis (Ed.), Inrernational reliew, of research in mental retardation (Vol. 7). New York: Academic Press, 1974. Bruce, D.. & Papay, J. P. Primary effect in single-trial free recall. Journal of Verbal Learning
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Butterfield, E. C.. & Belmont, J. M. Relations of storage and retrieval strategies as shortterm memory processes. Journal of Experimental Psychology. 1971, 89, 319-328. Epstein, W. Mechanisms of directed forgetting. In G. H. Bower (Ed.). The psychology of learning and motiwrion (Vol. 6). New York: Academic Press. 1972. Gibson, E. J. Principles of percepturrl learning and del*elopment. New York: AppletonCentury-Crofts. 1969. Hagen. J. W.. & Stanovich. K. G. Memory: Strategies of acquisition. In R. V. Kail &
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J. W. Hagen (Eds.), Perspectives on the development of memor?, and cognition. Hillsdale, N.J.: Erlbaum, 1977. Howard, D., & Goldin, S. Selective processing in encoding and memory: An analysis of resource allocation in kindergarten children. Journal of Experimental Child Psychology, 1979, 27, 87-95. MacLeod, C. M. Long-term recognition and recall following directed forgetting. Journul of Experimental Psychology: Human Learning and Memory, 1975. 104, 271-279. Reitman. W. R., Malin, J. T.. Bjork, R. A., & Higman. B. Strategy control and directed forgetting. Journnl of Verbal Learning and Verbal Behavior, 1973, 12, 140-149. Roediger, H. L. III. & Crowder, R. Cl. Instructed forgetting: Rehearsal control or retrieval inhibition (Repression)? Cognitive Psychology, 1972. 3, 244-254. Shiffrin, R. M., & Schneider, W. Controlled and automatic human information processing: II. Perceptual learning, automatic attending, and a general theory. Psycholug&/ Review, 1977, 84, 127-190. Wright, J. C., & Vlietstra, A. G. The development of selective attention: From perceptual exploration to logical search. In H. W. Reese (Ed.), Advances in child development and behavior (Vol. IO). New York: Academic Press, 1975.
RECEIVED: November 2, 1981: REVISED:August 2. 1982.