THE EFFECT OF DIFFERENT INTERPOLATED ACTIVITIES ON RETROACTION IN A VERBAL LEARNING EXPERIMENT. R.A.', University of British Columbia, 1956

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1 THE EFFECT OF DIFFERENT INTERPOLATED ACTIVITIES ON RETROACTION IN A VERBAL LEARNING EXPERIMENT by DOROTHEA ROSS R.A.', University of British Columbia, 1956 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF Master of Arts in the Department of Philosophy and Psychology We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA April, 1953

2 i i i THE EFFECT OF DIFFERENT INTERPOLATED ACTIVITIES RETROACTION '.IN A VERBAL LEARNING EXPERIMENT ON Abstract The purpose of this research was to investigate a methodological problem in tbe area of retroactive interference. Retroactive interference was defined as a decrement in retention resulting from an activity, usually a learning activity, interpolated between an original learning activity and a later measure of retention. Specifically, the problem was whether retroactive interference would occur, and in what amounts, when non-learning activities of increasing intensity were interpolated between the original learning material and a later measure of retention. Intensity was defined in terms of rate of manipulation and degree of complexity of a motor task. Certain relevant studies were discussed in terms of experimental variables that have been shown-to be functionally related to retroactive interference. One theoretical system, the perseveration theory, was considered briefly in connection with the intensity factor. Following the traditional retroaction paradigm, the general procedure was as follows: there were seven groups of subjects, an experimental group and six control groups. The original learning for all subjects consisted of a paired-associate list composed of nonsense syllables as stimuli and meaningful verbal materials as responses: the interpolated activities included a paired-associate list, a rest interval, a colornaming activity, and four systematic variations of a motor task along an intensity continuum. Retention was measured in terms of the number of correct anticipations made by the subject on the first relearning tfial (recall), and in terms of the number of trials required by the subject to reach the criterion on the original learning material (relearning). The amount and the direction of retroaction that occurred in each case was measured. Both the amount and the direction of retroaction differed significantly among the various groups. The bearing of these results upon the perseveration theory, and particularly upon the expectation which follows from it that retroactive interference varies with the intensity of the interpolated activity, was discussed. It was concluded that comparisons between retroaction experiments should be made with extreme caution i f the equivalence of the interpolated activities has not been empirically established..

3 ACKN01/VLEDGEMEMT The writer is greatly indebted to her advisor, Dr. D. T.! Kenny, for his active interest and helpful criticism during the course of this thesis. The writer also wishes to express her appreciation to the Department of Philosophy and Psychology for its generous provision of facilities and to those faculty members who contributed suggestions and criticisms. Special thanks are due to the one hundred Psychology students whose willing cooperation made this study possible.

4 iv CONTENTS Chapter page Abstract i i i I General Statement of the Problem 1 Review of related research U II Experimental Method 9 Subjects 9 Materials 9 Apparatus and Procedure 11 Design 11 III The Results and Their Statistical Treatment 14 IV Discussion 22 V Summary and Conclusions 26 References 28 Appendix A 30 Instructions Sample Record Sheet Appendix B 33 Analyses of variance for trials to reach the criterion on the original learning, number of correct responses on recall, and trials to reach the criterion on the relearning.

5 V TABLES Table page 1 Paired-associate lists 10 2 Means and S.D.'s of the OL trials 15 3 Means and S.D.'s of the recall trial compared with Group B 17 4 Means and S.D.'s of the recall trial compared with Group A 18 5 Means and S.D.'s of the RL trial compared with Group B 19 6 Means and S.D.'s of the RL trial compared with Group A 21

6 CHAPTER I GENERAL STATEMENT OF THE PROBLEM Many experiments have conducted on the conditions that produce forgetting. The results of these experiments have shown that, if we exclude the possibility that the major portion of forgetting may be explained by disuse or deterioration, forgetting is a function of three fundamental conditions: (a) interference by intervening activities; (b) altered stimulating conditions; and (c) inadequate set at the time of recall (15). The experimental work on forgetting as a function of intervening activities has nearly all been done under the name of retroactive interference (RI). This term refers to a decrement in retention resulting from an activity, usually a learning activity, interpolated between an original learning (OL) activity and a later measure of retention (5). This study is an investigation of a methodological problem in the area of RI. The problem is whether RI will occur, and in what amounts, when non-learning activities of increasing intensity are interpolated between the OL and a later measure of retention. Intensity is defined in terms of rate of manipulation and degree of complexity of a motor task. The concept of RI is more explicitly defined in terms of the operations by which i t is measured. Schematically, the experimental paradigm is as follows: Retroaction Paradigm Original Activity Interpolated Activity Retention Test Experimental learn A learn B recall-relearn A Control learn A rest recall-relearn A

7 a The subjects learn a given activity to some criterion and,, after an interval, are tested by one or more of the methods of measuring retention. The experimental and control conditions differ only with respect to the subjects' activity during the retention interval. Under the experimental condition a formally interpolated activity is introduced during the interval between the end of the practice of the OL and the later measure of retention: under the control condition there is no formal practice, but instead, the subject engages in some form of non-learning activity. Complete rest, in the sense of a psychological vacuum, would be desirable, but since that is impossible, a specific rest-interval activity is used in order that rehearsal and other experimentally undesirable effects may be controlled. In order to determine the effects of the different interpolated activities upon retention, it is important to ensure equivalent of OL under all conditions in a retroaction experiment; the only degrees variable allowed to operate is the interpolated activity. Any significant differences in retention must, then, be referred to the interpolated activity (15). As Osgood (18) has pointed out, this experimental design i s sometimes used without a clear understanding of its underlying assumptions. In the retroaction paradigm, the control group "rests" for the same temporal interval that the experimental group engages in the interpolated activity. The effects of the interpolated activity are then compared with the effects of the "rest" period. The practical justification given for using "rest" as a control condition is generally that "rest" renders the results of different

8 3 experiments comparable (18). This assumption implies that the effects of the interpolated "rest" periods will always be equivalent, which appears most unlikely since the character of these periods depends largely upon convention or a personal decision of an individual investigator. Since the reference level, i*e., performance of the control group, from which the amount and the direction of retroaction is computed may vary freely with the quality and the intensity of the "rest" activity, it is hard to see how different experiments are thus rendered comparable. However, procedures here are well standardized, and one only has to examine the experimental journals to see that comparisons between experiments by different investigators are frequently made (18)." In the present experiment, the OL consists of a paired-associate list which is learned by an experimental group and six control groups to a criterion of eight out of ten correct anticipations. Following the retroaction paradigm, each group is then assigned to one of seven different interpolated activities for the six minute period between the end of the OL and the beginning of the relearning (RL). These interpolated activities include a paired-associate list, a rest interval, a color-naming activity, and four systematic variations of a motor task along an intensity continuum. The problem is whether RI will occur, and in what amounts, when these different activities are interpolated between the OL and a later measure of retention. If the amount and/or direction of retroaction that occurs in each group differs significantly among the various groups, these results would suggest that comparisons between retroaction experiments should be made with extreme caution if the equivalence of the interpolated activities has not been empirically

9 4 established." More explicitly, the specific hypotheses to be tested in this experiment can be stated as follows: 1. When the performance of the traditional rest-control group is used as the reference level for the experimental group and the five activity-control groups, all these groups will exhibit RI. 2. When the performance of each of the five activity-control groups is used as a reference level for the experimental group, the amount and the direction of retroaction in the experimental group will vary with the quality and the intensity of the interpolated activities of these five activity-control groups. Review of related research Britt (1) reviewed the early work on RI in 1935J more recently, Swenson (21) surveyed the literature through McGeoch and Irion (15) provided a general summary of the literature through The review of studies relevant to this thesis will be presented i n terms of experimental variables that have been shown to be functionally related to Rll The section on experimental method will show how the experimenter either manipulated or attempted to hold constant each of these experimental variables which Bugelski (3) has described as some of the most significant variables in retroaction experiments. Similarity and retroaction The degree of similarity between the OL material and the interpolated activity i s the most important determinant of the retroaction effect (15). Similarity is not a single characteristic but a class of conditions that has many dimensions. One of the large number of possible relations between the OL and the interpolated activity in the retroaction paradigm is similarity of meaning^'

10 5 Similarity of meaning In an experiment using paired-associate learning, Osgood (16) used the same stimulus items during the OL and IL, but varied the response items in similarity of meaning. Three retroaction conditions were used: in the first condition, response Items in the OL and IL had similar meanings (elated - high); i n the second condition, neutrality prevailed (elated - left); and i n the third condition, the response items had opposite meanings (elated - low). The method of equated learning was employed. Osgood's results showed that, as response similarity increased (the stimuli remaining identical) amount of retroaction decreased! Amount of interpolated activity The fact that RI increases as a function of the amount of interpolated activity has been demonstrated with human subjects in rote verbal learning (5). However, Deese (5) has suggested that the sheer amount of interpolated activity may not be as important a variable as the amount of practice that the learner gives to the interpolated material. 1 Experimental evidence (15) indicates that the greatest amount of RI occurs in most situations when both the OL and the interpolated activity are carried to about the same degree. Time of Interpolation The time at which the interpolated activity occurs does not make very much difference (15). Different experiments with different conditions have shown that the greatest amount of RI is found if the interpolated activity occurs soon after the OL, or if the interpolated activity occurs just before the RL (1, 21): it does not seem to matter if the time interval between the OL and the RL is a long one or a short one (1). McGeoch and Irion (15) have suggested that further study of the temporal variable is needed before any generalized statements can be made about time of interpolation.

11 6 Warm-up effect Trion (9) has applied the concept of warm-up to retention. According to his hypothesis, during learning the subject acquired a certain set which facilitates his performance. This set is lost during the retention interval if the interpolated activity demands the assumption of other, incompatible, sets. At the time of recall or RL, the subject must reacquire the appropriate performance set. The period during which this resumption of set takes place is characterized by the rapid improvement of performance which is called the warm-up effect. A number of studies have shown the warm-up effect to exist in an RL curve, where its presence is revealed by the steeper slope of the RL curve.than-of the OL curve at the same initial level of performance (5). Thune (23) and Hamilton (6) have shown that a warm-up period before recall should improve retention. The warm-up activity should not provide the learner with practice on the habits in question. Thus, color-naming has been used as a warm-up activity in verbal learning. The colors are presented to the learner on the memory drum at the same rate as the paired-associates are learned, and the learner is required to vocalize rhythmically just as he does in the verbal learning situation. McGeoch and Irion (15) have stated that the amount of benefit to be derived from engaging in a warm-up task before the recall trial is a function of three variables: (a) the amount of the warm-up activity, (b) the similarity of the behaviors involved in the warm-up activity and the learning activity, and (c) the time interval between the warm-up activity and the recall trial. Intensity of the interpolated activity The perseveration theory of

12 7 Muller and Pilzecker (15) is related to the investigation of the intensity variable. The fundamental assumption of this theory is that a learned association requires some time to become set in the central nervous system after behavior has stopped. The exact nature of this setting-in process is unimportant, the important point is that a certain amount of rest is required after performing an act in order to allow time for that act to become established. Under the control or rest condition of the retroaction experiment, perseveration continues relatively unhampered by other stimulation which might inhibit it or diminish it in some way: by virtue of perseveration, the OL material is better learned and better retained. Many interpolated activities tend to suppress such a consolidating process, or to prevent if from running its full course, and as a result, the OL material is not as well retained.' Muller and Pilzicker (15) assumed that the amount of decrement should vary directly with the intensity of the interpolated activity on the ground that the more intense the interpolation, the greater would be the damping of the perseveration. This assumption is difficult to test directly since there are no direct measures of the intensity of most intervening activities (15). There is little in the extensive literature on RI which can be interpreted plausibly in support of the assumed relation between the intensity of the interpolated activity and the amount of decrement (5). Many experiments (15) have demonstrated the fact that fairly strenuous forms of interpolated activity do not produce any appreciable amount of RI, while interpolations such as tapping, colornaming, and reading plus shock, give very little decrement and may yield increments (10, 14).

13 8 Hovland (8) required his subjects to name colors at a moderate rate and found that this activity did not affect their recall scores, but Melton and Stone (13) urged their subjects to name colors as rapidly as possible and found that this activity resulted in lower recall scores. Withey, Buxton, and Elkin (27) required different rates of color naming during the interpolated period and found a slight superiority of scores for the condition where slow color-naming was used. Most authors (5, l t 18) have paid little or no attention to the intensity factor. McGeoch and Irion have stated: "In a very rough sense, however, it would seem that tapping, electric shock, and color-naming should be in the same region of intensity as practice on another list of words or learning another maze and that, therefore, they should yield approximately as much retroaction as such learning activities" (15, p. 434).

14 9 CHAPTER II EXPERIMENTAL METHOD Subjects.- The Ss were 70 male and female undergraduates volunteers enrolled in psychology courses at the University of British Columbia. All Ss had served in a verbal learning study (11) two weeks prior to the present experiment. This previous experience consisted of learning two lists of 15 paired-associates each on two consecutive days under experimental conditions that were almost identical to those in the present experiment. All Ss were naive with respect to the purpose of the experiment. Only right-handed Ss were used because a left-handed S would have required slightly different instructions. No S had had music lessens j,; l any experience with a metronome might have been an asset in the motor tasks, particularly in the speeded motor tasks. Materials.- The two paired-associate lists that were used in this experiment were composed of nonsense syllables as stimuli and meaningful verbal materials as responses. These two lists are shown in Table 1,' The ten nonsense syllables that were used as stimuli in both paired-associate lists were selected from Melton (IS) and were of low association value, averaging to 26.2$. The standard rules for the use of nonsense syllables were followed (18). The ten response words on the OL list were taken from the stimulus words on the Word Association List used in a study (11) done previously at the University of British Columbia. The ten response words on the IL l i s t were the most frequent responses made on the Word Association List (11) to the ten

15 10 TABLE 1 THE TWO PA TRED-ASSOCIATE LISTS USED AS OL AND IL TN THE EXPERIMENT ORIGINAL LEARNING INTERPOLATED LEARNING f (Based on R's from 684 Ss) CEX - SHEEP CEX - lamb 182 MOQ - HAMMER MOQ - nail 191 RUT - YOUTH RUT - young 201 G-AF - SOLDIER GAF - army 216 LIQ - FOOT LIQ - shoe 189 KOC - JUSTICE KOC - judge 181 QUZ - DARK QUZ - black 205 DEJ - EAGLE DEJ - bird 186 TAH - QUARREL TAH - fight 249 WOG - NEEDLE WOG - thread 263

16 11 stimulus words referred to above. Table 1 contains the associative frequencies from the norms for the ten stimulus words relevant to this experiment. All the response words appeared in the first 2,000 words of the Thorndike-Iorge (22) word list. Apparatus and procedure.- No practice was given because all the Ss were familiar with the procedure, the drum, the experimenter (E), and the room. On the day of this experiment each S was given standard instructions on paired-associate learning similar to those used in the previous study (11)j the exact instructions are contained in Appendix A. The ten paired-assocaates were presented on a Wichita Electronic Memory Drum, Model 241, at the rate of 2 sec. for the stimulus followed by the 2 sec. for the stimulus and response together. To control for serial position effects, each paired-associate list was presented in five different orders of pairs before the first order was repeated. Design.- The traditional retroaction paradigm (symbolized as A - Bj A - C; A - B) was followed. The Ss were randomly assigned to seven groups of ten Ss each. Each S learned one set of paired associates to a criterion of eight out of ten correct anticipations: then he was assigned to one of the seven different interpolated a c t i v i t i e s which required s i x minutes: finally, each S relearned the OL to the same c r i terion. The interpolated activities were as follows: Condition A - Experimental Group A learned the interpolated list of paired-associates shown in T able 1. Condition B - Control-Rest Group B "rested", during the interpolated activity period. During this interval E "worked" on the machine

17 12 and engaged the S in directed conversation so that the S did not talk about the OL period. The drum continued to turn at the same rate as that used in the OL but only blank paper appeared in the exposure window. Condition C - Control-Color Croup C named color patches fastened to the tape and exposed in the regular way, at the same rate as the OL, on the memory drum. Condition D - Control-Motor 1 Minnesota Formboard to the drum light Group D unloaded and loaded a flash at the same rate as that used in the OL. Each S was instructed to use only his right hand and to work in rows from right to left. Condition E - Control-Motor 2 Minnesota Formboard to the drum light Group E unloaded and loaded a flash at the rate of 60 pieces per minute, ^ach S was instructed to use only his left hand and to work in rows from left to right. Condition F - Control-Motor 3 Group F unloaded and loaded a Minnesota Formboard to the drum light flash at the rate of 120 pieces per minute.' Each S was instructed to use only his right hand and to work in rows from right to left. Condition G - Control-Motor 4 Group G unloaded and loaded a MfLnneosta Formboard to the drum light flash at the rate of 120 pieces per minute. Each S was instructed to use his right hand once and his left hand twoce and to work in rows from- right to left!' There was no special instructions given about rehearsal of the OL material in any of these conditions. Recording of the data.- All responses of the Ss were recorded. A sample record sheet is shown in Figure l. 5

18 13 Precautions to maintain set and avoid warm-up effects,- Since the recall scores were to be used as an index of RI, the following precautions were taken to maintain set and avoid warm-up effects. The room was so dark at all times that Ss had to be guided in and out by E. The light flash from the memory drum provided sufficient illumination for the motor tasks in conditions D, E, F, and G. The Ss remained seated during the entire experiment, and E was always seated to the right of S. The memory drum remained in front of S at all times and it ran without stopping from the beginning to the end of each S's session. The length of the interpolated activity (6 min.) and the time interval between the interpolated activity and the RL (30 sec.) was timed by stopwatch and was identical for all Ss. No attempt has been made to assess the relative importance of room, exposure device, and posture in furnishing incidental descriminative stimulation, however, E is satisfied that these conditions were as constant as possible for all Ss. Equality of lists.- A control study using two groups of ten Ss each was run to provide information about the relative difficulty of learning the OL and IL lists in a situation where transfer effects could not operate, since if the OL list were easier to learn than the IL list some of the results obtained could be accounted for on the basis of that factor alone. The 20 Ss in this control study had had experience identical to that of the 70 Ss in the experimental groups.

19 CHAPTER III 14 THE RESULTS AND THEIR STATISTICAL TREATMENT Equality of groups.- A statistical check was made to determine whether the Ss in each of the seven groups were equal in initial learning ability as indicated by the number of trials to reach the criterion on the OL. scores. Table 2 shows the means and standard deviations of these OL The F ratio was not significant (F «o!»22, p>.05). An evaluation of their performance records in a previous study (11 ) also showed the equality of these Ss, who subsequently formed the seven groups, in speed of learning paired-associates. It may be concluded that these groups were sufficiently comparable to allow direct intra-experimental comparisons. Equality of lists.- A control study was run to provide informati. ion about the relative difficulty of learning the OL and IL lists in a situation where transfer effects could not operate. In the absence of the possibility of transfer there was no evidence of easier learning of the OL list. The means for these two groups were 5.60 (SD m 1.83) and 5.80 (SD = 2.01), respectively. Correct responses at recall as an index of RI.- In a study of this type the first RL trial is a pure recall trial while the other trials necessarily involve some relearning. Thune and Underwood (24) stated that the results of their experiment bore out previous findings that recall scores provide a more sensitive:measure of RI than do RL scores. A record of all correct anticipations made on the first RL trial showed significant differences (F» 15.29, p<.05) in the rates of recall among

20 TABLE 2 MEANS AND STANDARD DEVIATIONS OF TRIALS REQUIRED BY EACH GROUP TO REACH THE CRITERION ON THE OL GROUP MEAN S.D. A ^61 B 5.80 ll25 C D E F G

21 16 the seven groups. The highest rate of recall was shown by the ^s in Group B and the lowest rate of recall was shown by the Ss in Group F, these recall scores are listed in Table 3. Table 3 shows the comparison between the reference level provided by the recall scores of Group B and those of each of the other six groups. RI took place in Groups A,E,F, and G. The amount of re troaction in Groups G and D was not significant, but the direction of retroaction was towards RI in these two groups. Table 4 shows the comparisons between the recall scores of Group A and those of Groups C, D f E, F, and G. The recall scores of Group A were significantly lower than those of Groups G and ^, i.e., RI took place in Group A. While the recall scores of Group A did not differ significantly from those of Groups E, F, and G, the direction of retroaction was towards retroactive Relearning as an index of RI.- facilitation in each case, The number of trials to reach the criterion on the RL is also used as an index of RI (16, 24), Table 5 shows that the pattern of differences in the R^ was similar to that shown in the recall record. The RL was fastest in Condition B and slowest in Condition G. Analysis of variance showed that the difference between the means of the various groups was significant (F = 3i.69, p<.05). Table 5 shows the results of the comparison between the reference level provided by the RL scores of Group B and the R^ scores of each of the other six groups. RI took place in Groups A, E, F, and G. The amount of retroaction in Groups C and D was not significant, but the direction of retroaction in these two groups was towards RI.

22 TABLE 3 MEANS AND STANDARD DEVIATIONS OF NUMBER OF CORRECT RESPONSES RECALLED BY EACH GROUP ON THE FIRST RE- LEARNING TRIAL. A COMPARISON OF EACH GROUP WITH GROUP B GROUP MEAN S.D. t value A B C D E I F S G I T Significant at the.05 level.

23 TABLE 4 MEANS AND STANDARD DEVIATIONS OF NUMBER OF CORRECT RE SPONSES RECALLED BY GROUPS A, C, D, E, F, AND G ON THE FIRST RELEARNING TRIAL. A COMPARISON OF EACH GROUP WITH GROUP A GROUP MEAN S.D. t value A C I D 7.SO I E ' 0.21 F G ff Significant at the.05 levels

24 TABLE 5 JEANS AND STANDARD DEVIATIONS OF TRIALS REQUIRED BY EACH GROUP TO REACH THE CRITERION ON THE RL. A COMPARISON OF EACH GROUP WITH GROUP B GROUP MEAN NO. OF TRIALS S.D. t value A I B S1 C D E I F I G I 5 Significant at the.05 level.

25 20 Table 6 shows the comparisons between the RL scores of Group A and those of Groups C, D, E, R, and G. The RL scores of Group A were not significantly different from those of any of these five control groups. When Group A was compared with Group C and Group D, the direction of retroaction in Group A was towards RI. The RL scores of Group A and Group E were identical. When Group A was compared with Group F and Group G, the direction of retroaction in Group A was towards retroactive facilitation. Overt intrusions at recall as an index of RI.- An overt intrusion is the giving of al IL list response in place of an OL list response when S is trying to recall the OL list in the first RL trial (15). Since the number of overt intrusions is one index of the amount of interference between the OL and the IL it is usually worthwhile to compute the number of overt intrusions which occur under each of the experimental conditions. A few intrusions occurred in the first RL trial among the Ss in Condition A. An occasional extra-list and intralist intrusion occurred in the control groups on this first RL trial. No statistical treatment was carried out because of t he low number of overt intrusions; the number of intrusions was probably lowered by the instructions - not to guess at random.

26 TABLE 6 MEANS AND STANDARD DEVIATIONS OF TRIALS REQUIRED BY GROUPS A, C, D, E, F, AND G TO REACH THE CRITERION ON THE RL. A COMPARISON OF EACH GROUP WITH GROUP A GROUP MEAN NO. OF TRIALS S.D. t value A C I D E S F G I ff Not significant at the.05 level.

27 22 CHAPTER IV DISCUSSION Other experimenters (5, 15) have used an experimental group and a control group, similar to Croup A and Group B, to demonstrate RI. The two indices of RI, recall and RL scores, showed clearly that, with Group B as a reference level, RI was present in Group A. A comparison of the recall and RL scores of each of the other fire control groups with the reference level provided by Group B showed that varying amounts of retroaction were present in these groups. RI was present in Groups E, F, and G. The direction of retroaction was towards RI in Groups C and D, but the amount of retroaction was not significant in either case. These results are consistent with previous findings (l, 21), both the time of interpolation (19) and the amount of interpolation (12) favored the production of RI in these groups. Generally, these results supported the first hypothesis of the experiment which stated that the performance of Group B was used as a reference level, RI would take place in the other six groups. The second hypothesis of this experiment was concerned with the effects of the different interpolated activities of the control groups on the amount and the direction of retroaction in the experimental group. A comparison of the recall and RL scores of Group A with the reference levels provided by each of Groups C, D, E, F,and G showed that both the amount and the direction of retroaction in the experimental group may vary with the quality and the intensity of the interpolated activity in the control groups.

28 23 If either Group C or Group D has been the control group for Group A, the recall scores would have demonstrated RI although the amount of RI would not have been as large as it was when Group B was used as the reference level. The RL scores would not have demonstrated RI, but the direction of retroaction would have remained towards RI On the basis of recall scores, a comparison of Group A with Group E would have shown a change in the direction of retroaction towards retroactive facilitation, since the recall scores of Group A were higher than those of Group E. The amount of retroaction was not significant however* The RL scores were identical in Groups A and E. A comparison of Group A with the reference levels provided by Groups F and G showed that the direction of retroaction was towards retroactive facilitation in both the recall and the RL scores. The amounts of retroaction were not significant in either case. The perseveration theory (15) implies that RI varies with the intensity of the interpolated activity rather than with its similarity to the OL material. The results of this experiment support this view* Groups G and D engaged in a color-naming activity and a motor task respectively during the interpolated intervale In comparison to the OL, the color-naming activity was overtly verbal and involved a slight learning of verbal connections, while the motor task was non-verbal and had no observable similarity to paired-associates. In each of these interpolated activities the same rate of responding

29 24 was required of the S. Tables 3 and 5 show that Groups C and D exhibited approximately the same amount of RI. The only differences between the interpolated activities of Group D and those of Groups E, F, and G was the increased rate of performance. That the intensity of the interpolated activities was greater in Groups E, F, and G than it was in Group D was shown in part by the fact that no S had any difficulty in keeping to the slow pace required in Group D, whereas 22 of the 30 Ss in Groups E, F, G showed some blocking, as well as signs of minor stress, at the and faster rates. The increased rate demanded of the Ss in Groups E, F, and G was reflected in the lower recall scores and the increased number of trials for RL, i.e., in increase in RI. The results obtained with Groups C and D support Hovland (8) whose Ss showed no increase in RI while working at a moderate rate. These results also confirm the statement of McGeoch and Irion (15) that color-naming and tapping are in the same region of intensity and should yield approximately the same amount of retroaction. The experimental data of Groups E, F, and G support Melton and Stone (13) and others (27) who found an increase in RI when the rate of performance was increased. It is difficulty to account for these results on any theoretical basis other than the perseveration theory, since intensity seems to be the only new factor in those groups where the greatest changes took place. The inference that increased intensity of activity will product RI by preventing perseveration thus finds some support in these results. The results of this experiment support the statement made by Thune and Underwood (24) and others (5, 15) that recall scores provide

30 25 a more sensitive measure of RI than do RL scores. Since the recall scores were to be used as an index of RI in this experiment, every effort was made to maintain the set of the Ss in the different groups. If the Ss had had to reacquire the appropriate performance set during the first RL trial, the recall scores could not have been used as an index of RI. The high degree of uniformity between the conditions renders valid the conclusion that the differences in retention must have been an outcome of the interpolated activities.

31 26 CHAPTER V SUMMARY AND CONCLUSIONS The purpose of this study was to investigate a methodological problem in the area of RI. Specifically, the problem was whether RI would occur, and i n what amounts, when non-learning activities of i n creasing intensity were interpolated between the OL and a later measure of retention in a series of retroaction experiments. This study was designed to show that the effects of interpolated activities are not always equivalent, and that, as a result of this finding, comparisons between retroaction experiments should be made with extreme caution if the equivalence of the interpolated activities has not been empirically established. More explicitly, the two hypotheses tested in this experiment were stated as follows: 1. When the performance of the traditional rest-control group is used as the reference level for the experimental group and the five activity-control groups, all these groups will exhibit RI. 2. When the performance of each of the five activity-control groups is used as a reference level for the experimental group, the amount and the direction of retroaction in the experimental group will vary with the quality and the intensity of the interpolated activities of these five activity-control groups. Following the traditional retroaction paradigm the OL material, a paired-associate list composed of nonsense syllables as stimuli and meaningful words as responses, was standard for all groups. The differ ences between the experimental conditions were found in the types of activity us d in the six minute interpolated period between the OL and

32 27 the RL. The RL consisted of further practice on the OL for all groups to a criterion of eight out of ten correct anticipations. The two indices of RI were the recall and the RL scores. Analysis of variance showed significant differences among the control groups in these two indices of RI. When the performance of the traditional rest-control group was used as a reference level, RI was present in the experimental group and three of the activity-control groups. A comparison between each of the five activity-control groups and the experimental group showed that both the amount and the direction of retroaction in the experimental group varied with the different-reference levels used. The results of this experiment supported the assumption made by Muller and Pilzecker (15) that the amount of decrement should vary directly with the intensity of the interpolated activity on the ground that the more intense the interpolation, the greater would be the damping of the perseveration. It is difficult to account for the results of this experiment on any other theoretical basis, since intensity seems to be the only new factor in those groups where the greatest changes took place. It is suggested that many of the more commonly used interpolated activities might be expected to produce similar variations in amount and direction of retroaction if they were examined systematically. It would be interesting to attempt to scale these activities in terms of their effects upon RL in retroaction experiments, or upon OL in transfer experiments. It is concluded that comparisons between retroaction experiments should be made with extreme caution if the equivalence of the interpolated activities has not been empirically established.

33 28 References 1. Britt, S.H. Retroactive inhibition: a review of the literature. Psychol. Bull., 1935> 32, Bugelski, B.R. Interference with recall of original responses after learning new responses to old stimuli. J. exp. Psychol., 1942, 30, Bugelski, B.R. The psychology of learning. New York: Henry Holt, Bunch, M.S. A comparison of retention and transfer of training from similar material after relatively long periods of time, J. exp. Psychol., 1941, 32, i 5. Deese, J. The psychology of learning. New York: McGraw-Hill, 1952, 6. Hamilton, C.E. The relationship between length of interval separating two learning tasks and performance on the second task. J. exp. Psychol., 1950, 40, Hilgard, E.R., and Marquis, D.G, Conditioning and learning. New York: Appleton-Century, Hovland, C.I. Experimental studies in rote-learning theory. 1. Reminiscence following learning by massed and by distributed practice. J. exp. Psychol., 1938, 22, Irion, A.L. The relation of "set" to retention. Psychol. Rev., 1948, 55, Irion, A.L., and Wham, D.S. Recovery from retention loss as a function of amount of pre-recall warming up. J. exp. Psychol., 1951, 41, Kenny, D.T. The contingency of verbal learning on implicit verbal chains. Unpublished study, University of British Columbia, Melton, A.W., and Irwin, «J, McQ. The influence of degree of interpolated learning on retroactive inhibition and the overt transfer of specific responses. Amer. J. Psychol., 1940, 53, Melton, A.W., and Stone, G.R. The retention of serial lists of adjectives over short time-intervals with varying rates of presentation. J. exp. Psychol., 1942, 30, McGeoch, J.A. The influence of four different interpolated activities upon retention. J. exp. Psychol., 1931, 14, McGeoch, J.A., and Irion, A.L. The psychology of human learning. New York: Longman's, 1952.

34 Osgood, C.E. Meaningful similarity and interference in learning,, J. exp. Psychol., 1946, 36, Osgood,..C.E. The similarity paradox in human learning: a resolution. Psychol. Rev., 1949, 56, Osgood, C.E. Method and theory in experimental psychology. New York: Oxford University Press, Postman, L., and Alper, T.G. Retroactive inhibition as a function of time of interpolation of the inhibitor between learning and recall. Amer. J. Psychol., 1946, 59, Russell, W.A., and Storms, L.H. Implicit verbal chaining i n paired-associate learning. J. exp. Psychol., 1955, 49, Swenson, Esther J. Retroactive inhibition: a review of the l i t e r ature. Minneapolis: Univ. Minnesota Press, 1941* 22. Thorndike, E.L., and Lorge, I, The teacher's word book of 30,000 words. New York: Bureau of Publications, Teachers College, Columbia University, Thune, L.E. The effect of different types of preliminary activities on subsequent learning of paired-associate material, J. exp. Psychol., 1950, 40, Thune, L.E., and Underwood, B.J. Retroactive inhibition as a function of degree of interpolated learning. J. exp. Psychol., 1943, 32, Twining, P.E. The relative importance of intervening activity and lapse of time in the production of forgetting. J. exp. Psychol., 1940, 26, Underwood, B.J. The effect of successive interpolations on retroactive, and proactive inhibition. Psychol. Monogr., 1945, 59 No Withey, S., Buxton, C.E,, and Elkin, A, Control of rest interval activities in experiments on reminiscence in serial verbal learning. J. exp. Psychol., 1949, 39,

35 APPENDIX A INSTRUCTIONS FOR PAIRED-ASSOCIATE LEARNING SAMPLE RECORD SHEET

36 INSTRUCTIONS FOR PAIRED-ASSOCIATE LEARNING This experiment is designed to test how rapidly you can learn ten paired items, when the stimulus of the paid which always appears on your left (ON THIS SIDE, pointing to the stimulus side of the window) is a nonsense syllable such a DOK and the response of the pair which always appears on your right (ON THE OTHER SIDE, pointing to the response side of the window) is a meaningful word. Don't worry about the pronunciation of the nonsense syllables because you never have to say them aloud. This is the procedure. First the nonsense syllable will appear for two seconds, then the same nonsense syllable will appear again with a meaningful word beside it like this (show DOK...DOK - superior, twice). Following the appearance of each nonsense syllable, you must learn to say the correct meaningful word out loud before that word is shown paired with the nonsense syllable. For example, as soon as you see DOK, try to say the correct word as quickly as you can. You do not have to wait until you are absolutely sure of the correct word because there is no penalty for guessing. On the other hand don't just guess at random because you'll get mixed up. Don't try to memorize the order of the pairs:- because the order will vary from one trial to the next. Now, on this first time through the series, watch the window and try to learn as many of the ten pairs as you can. I will tell you when you've seen all ten pairs. Beginning with the second run, try to say the meaningful word as soon as the nonsense syllable appears. Please don't ask me any questions about the purpose of the experiment. Are there any questions about the instructions?

37 FIGURE 1 SAMPLE RECORD SHEET Subject No. Sex Age Year Satisfactory 1. CEX - sheep 2. MOQ - hammer 3. RUY - youth 4. GAF - soldier 5. LIQ - foot 6. KOC - justice 7. QUZ - dark 8. DEJ - eagle 9. TAH - quarrel 10. WOG - needle ORIGINAL LEARNING TRIALS CEX - lamb 2. MOQ - nail 3. RUY - young 4. GAF - army 5. LIQ - shoe 6. KOC - judge 7. QUZ - black 8. DEJ - bird 9. TAH - fight 10. WCG - thread INTERPOLATED LEARNING TRIALS CEX - sheep 2. MOQ - hammer 3. RUY - youth 4. GAF - soldier 5. LIQ - foot 6. KOC - justice 7. QUZ - dark 8. DEJ ~ eagle 9. TAH - quarrel 10. WOG - needle RELEARNING TRIALS

38 APPENDIX B ANALYSES OF VARIANCE FOR TRIALS TO REACH THE CRITERION ON THE ORIGINAL LEARNING, NUMBER OF CORRECT RESPONSES ON RECALL, AND TRIALS TO REACH THE CRITERION ON THE RELEARNING

39 34 TABLE $ ANALYSIS OF VARIANCE OF TRIALS REQUIRED BY EACH GROUP TO REACH THE CRITERION ON THE OL SOURCE OF VARIATION SUM OF SQUARES df VARIANCE ESTIMATE F Between groups I Within groups Total IT Not significant at the.05 level of confidence.

40 35 TABLE 6 ANALYSIS OF VARIANCE OF NUMBER OF CORRECT RESPONSES RECALLED BY EACH GROUP ON THE FIRST RELEARNING TRIAL SOURCE OF VARIATION SUM OF SQUARES df VARIANCE ESTIMATE F Between groups 211.% Within groups Total Significant at the.05 level of confidence.

41 36 TABLE 7 ANALYSIS OF VARIANCE OF TRIALS REQUIRED BY EACH GROUP TO REACH THE CRITERION ON THE RL SOURCE OF VARIATION SUM OF SQUARES df VARIANCE ESTIMATE F Between groups I Within groups Total Significant at the.05 level of confidence.