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Effects of a subsidiary task on backward recall
JOURNAL
OF VERBAL
LEARNING
Effects
AND
VERBAL
BEHAVIOR
of a Subsidiary
7, 722-725
Task
MOTET
(1968)
on Backward
Recall*
MITSUDA
Department of Educational Psychology, Kyoto University, Kyoto, Japan This experiment was based on the assumption that a concurrent subsidiary task should adversely affect recall. In an experiment on the running memory span, 1 digit (male voice) and two-digit pairs (female voice) appeared alternately, and Ss were required to memorize the male voice series, while classifying, copying, or not processing each of the interpolated digit pairs. Recall performance was significantli impaired by interpolated activity, but equally so by classifying and copying. It is suggested that the subsidiary operation interfered with rehearsal.
In the establishment of memory through selective registration and fixation of stimulus information from the external world, rehearsal as a mnemonic operation serves as (a) a reactivator of the trace and as protection against the fading of the memory traces, (b) a source of supermotorial cues, (c) a means of distributing mnemonic effort through self-pacing, and (d) an item integrater (Umemoto, 1968). The results of previous experiments show that degree of distraction or attention given the intervening task in the memory-establishing process as noted above can be manipulated, and that this degree of distraction is systematically related to the amount of forgetting (Posner, 1966; Murdock, 1965). This finding has been interpreted by these authors in terms of the limited capacity of the information-processing system (e.g., Broadbent, 1958, Ch. 9). This interpretation leads to the conclusion that the effects of rehearsal mentioned above are determined by the processing capacity available. The aim of the present study is to extend these results to situations that confront Ss with a continuing sequence of items and require them to retain as much as possible of the most recently presented information. 1 The author is grateful to Dr. Takao Umemoto, Associate Professor of Kyoto University, for his help; and to Editor for his advice and criticism. 722
METHOD
Subjects. A group of 21 students from Kyoto University served as Ss. Seven Ss were assigned to each of three groups, each group being given a different type of information-processing task. Materials. Forty series of digits were recorded on tape and divided into two series of 20 each. Within each set there were four series each of 10,15, 17,20, and 25 digits spoken by a male voice. Between each digit spoken by the male voice, there were interpolated two digits spoken by a female voice, so that the one digit spoken by the male voice and two digits spoken by the female voice appeared alternately, at a rate of 60 digit/min. The sequence of events in the experimental session was as follows: “ready” - 1 digit (male voice), 2 digits (female voice) . . . IOth, 15th, 17th, 20th, or 25th digit (male voice) -recall (10 set) - “stop recording” - 5-set pause - next trial. Tasks. The three types of information-processing tasks were as follows. (a) Rest: In this task S was required to retain as many as possible of the most recently presented digits (male voice only) while no transform was required of the interpolated digit pairs (female voice), (b) Copy: In this task S was required to recall the digits spoken by the male voice in the manner described above, while writing down each of the interpolated digit pairs, (c) Two-Bit Classi’cation: In this task, the recall task was the same as described above, while Ss were required to write down “+” if each pair of interpolated digits was high (above 50) and even, or low (below 50) and odd, or “-‘I for reverse. Procedure. The Ss were given score sheets and wrote their transformations in the square corresponding to each interpolated digit pair, while trying to memorize the digit series presented by the male voice. After each series was completed, the Ss began to recall the series they had received. The Ss were instructed to record
723
SUBSIDIARY TASK IN RECALL only in the order of presentation, always starting with the most recent digits they could recall. All 5s began with three practice problems. The sequence of 20 series each was counterbalanced so that a given list length was preceded equally often by each of other four conditions of list length. RESULTS AND DISCUSSION
The number of items correctly recalled and positioned before the occurrence of a double
-l
D---&EST
.80-
the task means were evaluated by the NewmanKeuls procedure (Winer, 1962). The rest group was superior to both copy and classification groups (p < .OOl), and further analysis showed that this superiority was true for every level of list length. Serial-position curves for the task at every level of list length are shown in Fig. 1, each point being based on 56 cases (7 Ss tested 8 times).
-COPY e-+GELECT
.b@
.40.
‘:
2w
20.
=01,,
.
1,
LAST
-u
6
,
,
4
’
I
2
b- ~
LAST 13 11 -15 SERIAL POSITION
LAST
17
15 SERIAL POSITION
9
SERIAL ,.,.,.-s \ POS;TION(
FIG.
LI;T
LENGW
COW’
1. Serial position curves at backward recall as a function of subsidiary task and list length.
error in recall from the end of a series was determined for each S at every level of list length and was subjected to analysis of variance (Type I, Lindquist, 1953) with list length (within Ss) and information-processing tasks (between Ss) as main effects, after square-root transformation. The F for the task main effect was 17.90 (p < .OOl) and no other Fexceeded 1.OO.The differences between
The results show that despite the lack of strong evidence that classifying differs from copying, there is a significant’drop in proportion correct from rest to copying, suggesting a detrimental effect produced by interpolated activity. This finding, taken together with those obtained by Murdock (1965) would seem to point to rehearsal prevention, which could possibly account for recall depression.
724
MITSUDA
Previous findings (Postman, Turnage, and Silverstein, 1964; Pollack, Johnson, and Knaff, 1959) have suggested that in backward recall, list length affected the amount of recall owing to intra-serial interference developed during the exposure to the series. However, the present data failed to show a significant list-length effect. Furthermore, for each list length, serial-position curves showed a far steeper drop than those in previous studies. To what are those contradictions due? One possibility is that the difficulty of the information-processing operation had adverse effects on recall, and thus was not sensitive to the intraserial interference. It is also possible that, as a message of unknown length continues, Ss are increasingly set for the occurrence of the test and begin rehearsing the most recent items (Postman, Turnage, and Silverstein, 1964, p. 88). If so, the effects of a subsidiary operation should be reduced, whereas with a rehearsal-preventing activity, S would get further behind in his rehearsal as the list lengthens, and would give up at a certain distance from the end. The fact that a regular shift in maximum scores for the mean proportion of correct recalls (as scored for each of
the last few items and plotted against list length) was shown by two rehearsal-preventing groups (Fig. 2) and not by the rest group (Fig. 3) is not inconsistent with this notion. Thus though not statistically significant, list length may not be irrelevant in the determination of the effects of subsidiary operations on recall. Contrary to expectation, however, copying and classification yielded almost identical results. This result may not be inconsistent with the finding of Murdock (1965) that performance in free recall deteriorates when subsidiary card sorting is stressed, and that for the last four serial
.80
FOURTH LAST
ok
PlAX. \
LIST LAST
oh-.,,...,...,,,,,.,, 10
15 LIST
,,,l,r,,,l,r,,,,,, 10 15
17 20 LENGTH
25
FIG. 2. Mean proportion of correct recalls of each of the last few items for the rehearsal-prevention groups (copying and classification combined) as a function of list length.
17 20 LENGTH
FROM
25
FIG. 3. Mean proportion of correct recalls of each of the last few items for the rest group as a function of list length.
positions, the degrees of deterioration are indistinguishable, The present results could be explained better in terms of post-perceptual storage or a recency mechanism in recall (e.g., Peterson, 1966), that is, if S gets behind in rehearsal with a subsidiary task and/or with increasing list length, he would rely on such short-term storage, whose effectiveness decreases over time and the input of other information. Reference to Fig. 1 shows that recall scores for the most recent items, which could be
SUBSIDIARY
TASK
taken as a measure of original learning or registration, showed no appreciable differences among experimental conditions; any probably, the degree of original learning or registration would not be adversely affected by the subsidiary task. It is evident, then, that subsidiary tasks have an adverse effect on recall; however, the present data failed to show clearly a correspondence between the information-processing rate (Posner, 1966) for the subsidiary task and depression of recall, as was hypothesized in the introductory remarks. It is suggested that in the present experimental situation the nature of the subsidiary operation itself (e.g., switching between a male voice and a female voice) is a more critical factor than information-processing rate. Further experimental work will be necessary to clarify the relationship among those variables.
725
IN RECALL
REFERENCES BROADBENT, D. E. Perception and communication. New York: Pergamon, 1958. LINDQUIST, E. F. Design and analysis of experiments in psychology and education. Boston: Houghton Mifflin, 1953. MURDOCK, B. B., JR. Effects of subsidiary task on short term memory. Bit. J. Psychol., 1965,56,413-419. PETERSON, L. R. Short-term verbal memory and learning. Psychol. Reu., 1966,73, 193-207. POLLACK, I., JOHNSON, L., AND KNAFF, P. R. Running memory span. J. exp. Psychol., 1959,57,137-141. POSNER, M. I. Comments of skilled performance. Science, 1966,152,1712-1718. POSTMAN, L., TURNAGE, T., AND SILVERSTEIN, A. The running memory span for words. Quart. J. exp. Psychol., 1964,16,81-89. UMEMOTO, T. Coding behavior. In A Handbook of learning psychology. Tokyo: Kaneko-Shobo, in press. WINER, B. design.
J.
Statistical
principles
in
experimental
New York: McGraw Hill, 1962.
(Received July 14, 1967)
OF VERBAL
LEARNING
Effects
AND
VERBAL
BEHAVIOR
of a Subsidiary
7, 722-725
Task
MOTET
(1968)
on Backward
Recall*
MITSUDA
Department of Educational Psychology, Kyoto University, Kyoto, Japan This experiment was based on the assumption that a concurrent subsidiary task should adversely affect recall. In an experiment on the running memory span, 1 digit (male voice) and two-digit pairs (female voice) appeared alternately, and Ss were required to memorize the male voice series, while classifying, copying, or not processing each of the interpolated digit pairs. Recall performance was significantli impaired by interpolated activity, but equally so by classifying and copying. It is suggested that the subsidiary operation interfered with rehearsal.
In the establishment of memory through selective registration and fixation of stimulus information from the external world, rehearsal as a mnemonic operation serves as (a) a reactivator of the trace and as protection against the fading of the memory traces, (b) a source of supermotorial cues, (c) a means of distributing mnemonic effort through self-pacing, and (d) an item integrater (Umemoto, 1968). The results of previous experiments show that degree of distraction or attention given the intervening task in the memory-establishing process as noted above can be manipulated, and that this degree of distraction is systematically related to the amount of forgetting (Posner, 1966; Murdock, 1965). This finding has been interpreted by these authors in terms of the limited capacity of the information-processing system (e.g., Broadbent, 1958, Ch. 9). This interpretation leads to the conclusion that the effects of rehearsal mentioned above are determined by the processing capacity available. The aim of the present study is to extend these results to situations that confront Ss with a continuing sequence of items and require them to retain as much as possible of the most recently presented information. 1 The author is grateful to Dr. Takao Umemoto, Associate Professor of Kyoto University, for his help; and to Editor for his advice and criticism. 722
METHOD
Subjects. A group of 21 students from Kyoto University served as Ss. Seven Ss were assigned to each of three groups, each group being given a different type of information-processing task. Materials. Forty series of digits were recorded on tape and divided into two series of 20 each. Within each set there were four series each of 10,15, 17,20, and 25 digits spoken by a male voice. Between each digit spoken by the male voice, there were interpolated two digits spoken by a female voice, so that the one digit spoken by the male voice and two digits spoken by the female voice appeared alternately, at a rate of 60 digit/min. The sequence of events in the experimental session was as follows: “ready” - 1 digit (male voice), 2 digits (female voice) . . . IOth, 15th, 17th, 20th, or 25th digit (male voice) -recall (10 set) - “stop recording” - 5-set pause - next trial. Tasks. The three types of information-processing tasks were as follows. (a) Rest: In this task S was required to retain as many as possible of the most recently presented digits (male voice only) while no transform was required of the interpolated digit pairs (female voice), (b) Copy: In this task S was required to recall the digits spoken by the male voice in the manner described above, while writing down each of the interpolated digit pairs, (c) Two-Bit Classi’cation: In this task, the recall task was the same as described above, while Ss were required to write down “+” if each pair of interpolated digits was high (above 50) and even, or low (below 50) and odd, or “-‘I for reverse. Procedure. The Ss were given score sheets and wrote their transformations in the square corresponding to each interpolated digit pair, while trying to memorize the digit series presented by the male voice. After each series was completed, the Ss began to recall the series they had received. The Ss were instructed to record
723
SUBSIDIARY TASK IN RECALL only in the order of presentation, always starting with the most recent digits they could recall. All 5s began with three practice problems. The sequence of 20 series each was counterbalanced so that a given list length was preceded equally often by each of other four conditions of list length. RESULTS AND DISCUSSION
The number of items correctly recalled and positioned before the occurrence of a double
-l
D---&EST
.80-
the task means were evaluated by the NewmanKeuls procedure (Winer, 1962). The rest group was superior to both copy and classification groups (p < .OOl), and further analysis showed that this superiority was true for every level of list length. Serial-position curves for the task at every level of list length are shown in Fig. 1, each point being based on 56 cases (7 Ss tested 8 times).
-COPY e-+GELECT
.b@
.40.
‘:
2w
20.
=01,,
.
1,
LAST
-u
6
,
,
4
’
I
2
b- ~
LAST 13 11 -15 SERIAL POSITION
LAST
17
15 SERIAL POSITION
9
SERIAL ,.,.,.-s \ POS;TION(
FIG.
LI;T
LENGW
COW’
1. Serial position curves at backward recall as a function of subsidiary task and list length.
error in recall from the end of a series was determined for each S at every level of list length and was subjected to analysis of variance (Type I, Lindquist, 1953) with list length (within Ss) and information-processing tasks (between Ss) as main effects, after square-root transformation. The F for the task main effect was 17.90 (p < .OOl) and no other Fexceeded 1.OO.The differences between
The results show that despite the lack of strong evidence that classifying differs from copying, there is a significant’drop in proportion correct from rest to copying, suggesting a detrimental effect produced by interpolated activity. This finding, taken together with those obtained by Murdock (1965) would seem to point to rehearsal prevention, which could possibly account for recall depression.
724
MITSUDA
Previous findings (Postman, Turnage, and Silverstein, 1964; Pollack, Johnson, and Knaff, 1959) have suggested that in backward recall, list length affected the amount of recall owing to intra-serial interference developed during the exposure to the series. However, the present data failed to show a significant list-length effect. Furthermore, for each list length, serial-position curves showed a far steeper drop than those in previous studies. To what are those contradictions due? One possibility is that the difficulty of the information-processing operation had adverse effects on recall, and thus was not sensitive to the intraserial interference. It is also possible that, as a message of unknown length continues, Ss are increasingly set for the occurrence of the test and begin rehearsing the most recent items (Postman, Turnage, and Silverstein, 1964, p. 88). If so, the effects of a subsidiary operation should be reduced, whereas with a rehearsal-preventing activity, S would get further behind in his rehearsal as the list lengthens, and would give up at a certain distance from the end. The fact that a regular shift in maximum scores for the mean proportion of correct recalls (as scored for each of
the last few items and plotted against list length) was shown by two rehearsal-preventing groups (Fig. 2) and not by the rest group (Fig. 3) is not inconsistent with this notion. Thus though not statistically significant, list length may not be irrelevant in the determination of the effects of subsidiary operations on recall. Contrary to expectation, however, copying and classification yielded almost identical results. This result may not be inconsistent with the finding of Murdock (1965) that performance in free recall deteriorates when subsidiary card sorting is stressed, and that for the last four serial
.80
FOURTH LAST
ok
PlAX. \
LIST LAST
oh-.,,...,...,,,,,.,, 10
15 LIST
,,,l,r,,,l,r,,,,,, 10 15
17 20 LENGTH
25
FIG. 2. Mean proportion of correct recalls of each of the last few items for the rehearsal-prevention groups (copying and classification combined) as a function of list length.
17 20 LENGTH
FROM
25
FIG. 3. Mean proportion of correct recalls of each of the last few items for the rest group as a function of list length.
positions, the degrees of deterioration are indistinguishable, The present results could be explained better in terms of post-perceptual storage or a recency mechanism in recall (e.g., Peterson, 1966), that is, if S gets behind in rehearsal with a subsidiary task and/or with increasing list length, he would rely on such short-term storage, whose effectiveness decreases over time and the input of other information. Reference to Fig. 1 shows that recall scores for the most recent items, which could be
SUBSIDIARY
TASK
taken as a measure of original learning or registration, showed no appreciable differences among experimental conditions; any probably, the degree of original learning or registration would not be adversely affected by the subsidiary task. It is evident, then, that subsidiary tasks have an adverse effect on recall; however, the present data failed to show clearly a correspondence between the information-processing rate (Posner, 1966) for the subsidiary task and depression of recall, as was hypothesized in the introductory remarks. It is suggested that in the present experimental situation the nature of the subsidiary operation itself (e.g., switching between a male voice and a female voice) is a more critical factor than information-processing rate. Further experimental work will be necessary to clarify the relationship among those variables.
725
IN RECALL
REFERENCES BROADBENT, D. E. Perception and communication. New York: Pergamon, 1958. LINDQUIST, E. F. Design and analysis of experiments in psychology and education. Boston: Houghton Mifflin, 1953. MURDOCK, B. B., JR. Effects of subsidiary task on short term memory. Bit. J. Psychol., 1965,56,413-419. PETERSON, L. R. Short-term verbal memory and learning. Psychol. Reu., 1966,73, 193-207. POLLACK, I., JOHNSON, L., AND KNAFF, P. R. Running memory span. J. exp. Psychol., 1959,57,137-141. POSNER, M. I. Comments of skilled performance. Science, 1966,152,1712-1718. POSTMAN, L., TURNAGE, T., AND SILVERSTEIN, A. The running memory span for words. Quart. J. exp. Psychol., 1964,16,81-89. UMEMOTO, T. Coding behavior. In A Handbook of learning psychology. Tokyo: Kaneko-Shobo, in press. WINER, B. design.
J.
Statistical
principles
in
experimental
New York: McGraw Hill, 1962.
(Received July 14, 1967)