the effects of prolonged learning on learning

JOURNAL OF VERBAL LEARNING AND VE~BAL BEXAVIOR 1, 173-182 (1962)

The Effects of Prolonged Learning on

WILSE B. WEBB 1'2

University o] Florida, Gainesville, Florida

Learning

In today's search for accelerated learning procedures, there is a serious need for the answer to a core question which presents it- self: within a single learning session, what are the limits of effective learning? Specific- ally stated, what happens to the effectiveness of learning as a function of amount of preceding learning activity within a single session of learning? Still another way of ex- pressing this problem would be as follows: if an individual learns x amount in y time, does 2y time yield 2x learned, and 3y time yield 3x, etc., or is x a decreasing function of increasing amounts (time) learned?

The review of the literature reveals a scat- tered but persistent interest in the general problem of prolonged learning. D. O. Lyon, in his monograph Memory and the Learning Process (1917), cites Ebbinghaus' early study reported in his classic UTher das Gediichtnis which plots the repetitions required as the number of syllables were extended from 7 to 36. He also reviews the work of Binet (1894), Binet and Henri (1894), and the early studies of Neumann (no year) and Henmon (1917). In all of these studies, the concern centered on the number of repetitions required for learning as the amount of material within the list to be learned was increased. For example, in the Binet and Henri study, the number of seconds required to learn 10, 15, 20, etc., up to 200, digits was deter- mined. Lyon, in his study, extended this work to include lists of 72 nonsense syllables and up to 1500 words of prose-poetry material within a single learning session. Lyon extended the amount to-be-learned up to 15,000

1 This research was supported by ONR Contract 580(07).

2 Gratitude is extended to John Wipf and Gordon Gibson, who were assistants in this project.

words of prose-poetry material, using a once- a-day learning procedure. A more recent related study is that of Cofer (1941) which again extends the amount of material to-be- learned.

All of these studies had in common the procedure of increasing the amount of the material to be learned, i.e., each condition involved a greater and greater number of syllables or number of digits or length of the prose passage. This procedure has two de- ficiencies from our viewpoint: (1) The nature of the task and the period of learning were different from group to group, i.e., learning one stanza of poetry is considerably different in terms of interference and fatigue, etc., from learning 200 stanzas, as well as differing in length of time at the task. (2) The efficiency of learning at various stages of the learning process and recall process, as such, were not reported and would be difficult to obtain.

As a result of our review of the literature on prolonged learning, this study used a constant learning task throughout the process of learning and varied only the amount previously learned (and, of course, the time to learn) by a subject. The method used is de- tailed in the procedure section but in essence each subject learned a single set of six paired associates, then a second, a third, etc. The design thus was more similar to the well known proactive and retroactive designs than the previously noted length-of-material designs. Again, within this design, however, there were no data directly relevant to our general problem since these later studies, in each instance known to the experimenter, used a once-per-day session for learning, and the longest of these sessions lasted only one hour, e.g., in the studies of Luh (1922), Ward (1937), Hovland (1940), and Youtz (1941).

173

174 WEBB

T h e p u r p o s e o f t h e s t u d y , t h e n , w a s to a s s e s s t h e e f f i c i ency o f l e a r n i n g per se o v e r

p r o l o n g e d a n d c o n t i n u o u s s e s s i o n s ( s ix h o u r s ) u s i n g h u m a n Ss l e a r n i n g v e r b a l m a t e r i a l . I t

w a s d e s i g n e d to e x p l o r e b o t h t h e l e a r n i n g a n d

r e t e n t i v e a s p e c t s o f s u c h p r o l o n g e d se s s ions .

METHOD

Length o] Sessions The length of sessions was six successive, con-

tinuous hours of learning. The time chosen was one considerably longer than any time periods used in previous studies. On the other hand, it was a period of time limited so as to avoid complications of hunger, gross fatigue, and, of course, the limitations of the E. Approximately 4986 trials (stimulus-stimulus-response presentations) could be given within this time period.

Materials Used It was decided to use the classical paired-associate

procedure for ease of measurement, a n d English- Russian vocabulary was chosen as the specific material. Methods for developing the particular items were as follows:

In an at tempt to increase the homogeneity of difficulty of the response item, two-syllable pronounce- able Russian words with low apparent meaning similarity to English words, and low similarity to the English stimulus words were selected. Further, English words with high apparent emotional content or low general familiarity were eliminated. Word pairs were selected from The Dictionary o] Synonyms in the Principal Indo-European Languages (Buck and others, 1949).

The listing of two-syllable Russian words did not yield sufficient word pairs to meet our criteria; therefore, one-syllable and three-syllable words were modified to two-syllable words by the adding or eliminating of syllables. The final lis~ of 726 word pairs consisted of 73% unmodified English-Russian words and 27% "edited" pairs. The Russian words were, of course, transliterated from the Cyrillic. 3

Method o] Presentation The 726 word pairs were randomly assigned to 121

lists of six word pairs each. The six pairs in each list were arranged in three different serial orders for the word pairs. For a given set of six pairs, a film strip was photographed with the first frame being the stimulus word of the first pair of words, the second frame being the stimulus word and the re-

3 Lists used are presented in ONR final report, "The Effects of Prolonged Learning on Learning."

sponse word; the third frame, the stimulus word of the second pair; the fourth frame, the second stimulus word and the second response words, etc. Twelve frames, constituting one presentation of the six pairs, were followed by a blank frame. Stimulus word and word pairs were then presented in a different serial order for twelve frames followed by a blank frame and then a third serial order of the stimulus word and the word pairs was presented and followed by a blank frame. This 39-frame strip was then spliced into a loop, thus 121 film-strip loops were produced. The exception among these 121 loops were 12 loops in which the serial order was kept constant.

Two 35-mm film-strip projectors were then mounted side by side with a common projection area. These projectors were modified to permit a timed presentation for each frame. A standard 2-sec. presentation rate was employed.

By employing looped strips, a given list of word pairs could be run continuously in three different orders until the S had reached the learning criterion. Immediately upon completion of a list the second projector was activated. This projector had been loaded during the first presentation of the previous list during which learning could not be expected and hence required no recording.

Order o] List Presentation In order to test for both the effects on learning

and retention, the basic pat tern of learning was that of three new lists followed by a recall list. In the first block of 12 list presentations, Lists 1, 2, and 3 were followed by a recall of List 1. This was followed by three new lists, Lists 4, 5, and 6, followed then by a recall of List 4. Then a presentation of Lists 7, 8, and 9, followed by a recall of List 2. This block of 12 then consisted of nine new lists and three recall lists; two of the recalls occurred after two interpolated lists and one recall occurred after the interpolation of nine lists, of which two were recall lists. This pat tern was again used in the second 12 list presentations and the .third 12 list presentations. In the third set of 12 list presentations, the last list, rather than being a recall with nine interpolated lists, was a recall of the list presented as the third new (List 3) list. In other words, the latter was a recall after 32 interpolated lists. The 37th list presentation was the recall of the list learned on the 15th presentation (List 12), or a recall after 21 interpolated lists. In summary, then, the first 37 list presentations consisted of six recalls after two interpolated lists, two recalls after nine interpolated lists, one recall after 21 interpolated lists, and one recall after 32 interpolated lists. Each list used as a recall list was preceded by varying amounts of prior

EFFECTS OF PROLONGED LEARNING ON LEARNING 17 5

learning, e.g., the fourth new list was learned after three new lists and a recall of List 1. The tenth new list, for example, was learned after nine new lists and three recall lists. In each of these instances, the amount of retroactive interpolation was the same- - two new lists being interpolated between learning and recall. This same pattern was used for the next 37 lists so that after 74 units of learning, 54 new lists had been learned and 20 recall lists had been introduced. The pat tern was again repeated for 37 additional lists or presentations. On estimates from other learning studies, it was anticipated that this number of lists (81 new lists and 30 recall lists) represented sufficient learning materiaI for six hours.

As will be noted below, a second order of presentation of the lists, utilizing the same pattern of presentations, was also used.

Subjects The Ss were all male students at the University

of Florida. As we were concerned only with the learning process, no at tempt was made to select a random or representative group of Ss. The Ss were obtained by posting a notice on the bulletin board, asking for volunteers to be paid $2.00 per hour to take par t in a learning experiment and to be available for at least a six-hour period.

After 27 Ss had been run, not all of whose data were useful, a preliminary analysis of the data indicated considerable list heterogeneity. This list heterogeneity was particularly damaging in the analysis of the recall data. Further, although the lists were originally randomly distributed, it was desirable to re-order the lists to minimize possibility of a list- order effect. To do this, the lists were re-ordered ac- cording to the following rules.

First, the twenty most similar lists were selected from the first 54 new lists which made up the first 72 presentations of new lists and recall lists. These twenty lists then became the new recall lists in a new ordering. They were introduced in order by placing the last of these seleoted lists first, the next to last second, the third from the last becoming the third to-be-recalled fist, and so on until the twenty recall lists were completed. 4 The remaining 37 lists were redistributed by placing the last unused list (72) in the first unused (non-recall) position (7). The last 27 non-recall lists in presentation positions from 73-111 were simply reversed in their order: 109 became List 73; 108 became List 74, etc. This rather comp!ex re-ordering was primarily dictated by cur at tempting first to obtain homogeneously difficult recall lists; these were drawn from the first 72

4 List ordering is detaiIed in ONR final report, "The Effects of Prolonged Learning on Learning."

presentations since beyond that N of lists the N of cases becomes sharply reduced, making cur estimates of difficulty less certain. The decision to reverse the orders was a somewhat arbitrary one, directed to- ward maximally redistributing any systematic list effect.

Under the new ordering, 12 useable Ss were run. The Ss run under the original order will be referred to as Group I, and the Ss run under the second list order will be referred to as Group II.

Instructions The Ss were told that this was to be a study in

the learning of English-Russian vocabulary and were told that they would be expected to learn a considerable amount of material continuously and with no rest breaks. The Ss were told they would not receive pay unless they continued to learn until the E indicated that the experimental session was completed.

Experimental Setting The sessions were run in a quiet, well-lighted room.

Artificial lighting was used. The Ss were seated in a comfortable, stuffed lounge chair and provided with a toilet facility beside the chair. (No Ss used this facility.) They were seated approximately 10 ft. from a classroom movie screen. The projectors were above and behind the S. The words projected were approximately 6 in. in height and clearly visible to all Ss. Smoking was permitted. Most Ss were tested from approximately noon until 6 P.~. Four Ss in Group I and three in Group II were run in the evening.

RESULTS

F o r e a c h S t h e N of t r i a l s to r e a c h a cr i - t e r i o n o f o n e c o r r e c t r e p r o d u c t i o n w a s re -

c o r d e d , a n d r e p r e s e n t s t h e b a s i c d a t a for a n a l y s i s . 5 T a b l e 1 p r e s e n t s t h e N of l i s t s l e a r n e d fo r e a c h S for t h e t w o g r o u p s .

F o r p u r p o s e s o f a n a l y s i s , o n e spec i a l t r e a t - m e n t w a s g i v e n t h e scores . D u r i n g t h e l e a r n i n g

p r o c e s s i t w a s n o t e d t h a t fo r a l a r g e N of t h e

Ss , t h e r e w a s a n a p p a r e n t " b l o c k i n g " in l e a r n i n g . O n o n e or t w o l i s t s a S w o u l d c o n - s i d e r a b l y e x c e e d h i s o w n a v e r a g e r e q u i r e m e n t s fo r l e a r n i n g t h e l i s t in q u e s t i o n . T h e s e m a r k -

e d l y d e v i a n t s c o r e s w e r e t r e a t e d as s p e c i a l ca ses a n d r e p l a c e d b y "normalized" s c o r e s for t h e g e n e r a l a n a l y s i s o f t h e e f fec t s o f p r o -

5 Individual trial data are present in ONR final report, "The Effects of Prolonged Learning on Learning."

176 WEBB

TABLE 1

NUMBER OF LISTS LEARNED BY SUBJECTS

(ORDERED BY LEARNING RATE)

N u m b e r of l is ts l ea rned

Subject 1 Group I 33 Group II 53

Subject 7 Group I 78 Group II 107

Subject 13 Group I 93

2 3 4 5 6

33 37 53 65 67

60 70 77 87 96

8 9 10 11 12

78 79 83 86 86 108 111 111 111 111

(5:53) ~ (5:50) a (5 :16) a (4 :51) a

14 15 16 17 18 102 111 111 111 111

(5 :48) a (5 :45) a (3 :45) a (3 :30) a

a T i m e to comple te .

longed learning. The "normalizing" procedure was as follows.

When a score doubled the S's average N of trials on the preceding two lists and succeeding two lists, and in addition was at least 1 ~ times the score of the four adjacent Ss on the list in question, a new score was assigned. The assignment was made by making this score equal to the highest score of the four adjacent Ss (the Ss being arranged on a rate of learning order), unless this was less than the highest score made by the Ss on the two preceding and succeeding lists in which case the latter score was assigned.

The N of such "blockings" occurring, and their point of occurrence are reported as a part of the results below.

Analyses o~ Learning Effects There were, of course, wide variations in

rate of learning among the Ss used, as may be noted in Table 1. In order to analyze the learning process over as many Ss as possible, a form of Vincentized scores were used. Two central analyses were first performed; one concerned the effects of six hours of learning on learning, the second the effect of 77 learning lists on learning. In the first instance, while time was held constant, the amount learned varied considerably and in the second analysis, while the amount learned was held constant, the time and trials required to learn was a variable factor.

Rate o/ Learning during Six Consecutive Hours o~ Learning. For this analysis all Ss

in both groups who had continued to learn for at least 5 hr. 15 min. were included. The total population in this analysis included, then, 16 cases from Group I and 11 cases from Group II .

For each S the total N of trials on new lists (non-recall) was obtained. The obtained N of trials for each S was then divided into sixths. The N of list learned in each sixth of the trials was calculated. For example, if the S had received 3600 trials (list presentations) the N of lists learned during the first, second, and third, etc., units of 600 trials was calculated. Parts of lists learned within the sixths were treated as follows: I f ten lists had been learned in the first 585 trials and the next list required thirty trials to learn, the S was given credit for one-half list in the first sixth and one-half list in the second sixth.

Figure 1 presents the mean N of lists learned in each sixth of learning for the two groups. An analysis of variance (Type I) yielded a significant effect for sixths of learning (F --~ 3.69, d/ = 5/125, P < .005) and an F of 2.78 ( d / = 1/25, P < .20) for groups. An interesting finding was a highly significant linear trend component (P < .001) and quadratic component of the trend across sixths which was significant at the .05 level.

Rate oJ Learning over 77 Lists. In this analysis, it was necessary to choose an amount of learning which was considerable, but not so great as to eliminate too large a group of Ss. To this end the total of 77 lists, or 57 new lists learned, was chosen. This permitted re-

EFFECTS O F PROLONGED LEARNING ON LEARNING 17 7

12.0

11.5

I1.0

10.5

io.o

= 9 .5 g ® 9 . 0

8 . 5

8 . 0

o - - - o Group I

o-- . - - -o Group II

: s Groups I & II

/ / J a x \ \ ~ ~ " ° ~ / /

/ x \ / "°~" / /" ~" %./" /

"---..oi-" - . . ~ "

' ' ' 4'th 5'th J O ~ I st 2nd 5rd 6 th

Sixths

FIG. 1. Mean lists learned in sixths of total learning.

taining 12 Ss from Group I and nine Ss from Group II .

For these Ss, then, the total trials required to learn the first 57 new lists was obtained. These trials were then divided into sixths and the N of lists in each sixth was calculated for each S. For example, if a S required 600 trials to learn these lists, the N of lists learned in his first 100 trials was calculated in the manner described above and in the second 100 trials, etc. If, on the other hand, the S required 900 trials to learn these lists, the N of lists learned in the first 150 trials, second 150 trials, etc., was calculated.

Figure 2 presents the mean N of lists learned in each sixth of 57 new lists (77 serial presentations). A Type I analysis of variance yielded a significant effect for sixths

o--.--o Group II /\£.

II.O}F - - Groups 18, I I

~,o.~ r- / \. --~ I0.0 F .~x \

"~ 9.5 ~- \ '

~ 9.0

8.0

0 Ist 2nd 5rd 4 h 5th 6th

Sixths

Mean lists learned in sixths of 77 lists. Fxc. 2.

of learning (F ~ 1.65, d] z 5/95, P < .001) and for the Sixths X Groups interaction (F = 4.78, d/ -~ 5/95, P < .01).

A Selected Analysis o/ "Early" and "Late" Learning. In an attempt to determine if there was deficiency in learning which had accrued from prolonged learning, list difficulty and individual learning rates were controlled in a further analysis. The procedure was to select five lists that appeared early in Group I learning (within the first ten lists) and which also appeared late in learning for Group I I (between the 67th and 72nd list presentations). Further, five lists that appeared late in Group I were selected (between the 62nd and 71st list presentations) which also were used as early learning lists for Group I I (before the 15th list presentation). The lists so chosen are given in Table 2. From this table

T A B L E 2

LISTS AND MEANS OF IDENTICAL LISTS LEARNED

EARLY IN LEARNING AND LATE IN LEARNING a

"Late Hsts" "Early lists"

List Mean List Mean

Group I Group I I 72 11.0 7 9.4 68 8.8 3 8.6 67 11.4 6 10.2 66 5.0 9 5.2 64 11.4 10 12.0

Group I I Group I 62 11.0 3 10.4 68 7.O 14 10.2 67 9.0 6 8.2 71 11.2 7 11.8 70 6.8 13 4.8

a "Late" M ---~ 9.46; "Early" M ---- 9.08.

it may be seen that List 3 in Group I was learned as List 62 in Group I I ; List 72, late in learning for Group I, was learned as List 7 by G r o u p I I . These lists provide a comparison of rates of learning for identical lists acquired after considerable learning or early in learning.

In order to make this as "pure" an analysis as possible, Ss from the two groups were paired on their over-all learning rates. I t was found that five Ss could be matched almost

178 WEBB

identically from the two groups: Ss 14, 18, 19, 20, and 21 from Group I and Ss 1, 4, 5, 6, and 7 from Group II . I t can be seen from Table 1 that the overall learning rates of these Ss by pairs are almost identical; e.g., S 14 from Group I learned 78 lists and S 6 from Group I I learned 72 lists. The total lists learned by the two groups were 469 and 474, respectively, for the Group I and Group I I Ss.

An analysis of variance of the Early-Late by Lists effects produced no significant difference between early and late learning. There was a significant list effect.

Blocking. One final set of data related to ease and difficulty of learning may be noted. As indicated early in the description of the data, for a significant proportion of the population (25 of 32 Ss in the two groups) a blocking would occur at one or more points in the learning process. This was defined as a list which took at least twice as long as the two preceding or two succeeding lists to learn. The N of "blockings" in each third of learning for all the Ss who completed six hours of learning or exhausted the lists used were counted. There were 7 "blocks" in the first third of learning, 16 in the second third, and 8 in the last third. Of the 25 "blocking" Ss, six "blocked" in the first third, 13 in the second third, and 6 in the last third.

E~ciency of Recall in Prolonged Learning To interpret the increased efficiency of

learning, or at least the maintenance of efficiency of learning, in spite of the probability of considerable fatigue and interference, our design required us to explore a critical question: Have the Ss simply learned to forget quickly the previously learned lists and therefore learned lists quickly which were again to be quickly forgotten?

For the 111 lists there were eighteen recall lists with two interpolated learning lists; six recall lists with seven learning lists and two relearning lists interpolated; three lists with fifteen learning lists and six relearning lists interpolated; and three lists with twenty-four learning lists and eight relearning lists interpolated.

I t is clear, of course, that for each of these

lists the recall list was preceded by varying amounts of prior learning. The N of prior lists learned before the Recall 2 (two learning lists interpolated) lists, is, for example, the serial number of the list minus four. For example, the 8th list presented was a Recall 2 list with four prior lists learned (three learning lists and one recall list). Or again, the 32nd list presented also had two learning lists interpolated (a Recall 2 list) but with twenty- eight prior lists learned (twenty-one learning lists and seven recall lists).

An analysis of variance of the original learning measures on the recall lists in Group I revealed that there was considerable heterogeneity in the difficulty of these lists and further, the trends occurring in recall directly reflected the difficulty level of original learning. In an attempt to overcome this problem directly, twenty lists were selected from Group I which were not significantly different in learning rates for that group. These were then introduced as the to-be-learned lists for Group I I and fixed in the new ordering of lists as recall lists. This attempt to homogenize the original learning rates for recall was generally successful. An analysis of variance of the rates of acquisition of all of the learning lists (minus List 1) resulted in an F which was not significant at the 10% level of con- fidence. Our analysis then proceeded using the data from Group II .

The recall measure used was a savings score, i.e., N original learning trials minus N of recall learning trials (to a criterion of one perfect recall) divided by the iV of original learning trials, and multiplied by 100 to con- vert to a percentage.

The means for the various recall lists are given in Table 3. These means are grouped by the four conditions of retroactive interpolations of lists, i.e., those with two retroactive interpolations, nine retroactive interpolations, twenty-one retroactive interpolations and thirty-two retroactive interpolations. Within each group, the N's of prior lists learned are also given. For the "two" and the "nine" interpolation conditions, two sets of means are given, one of which includes ten Ss and the other includes seven Ss, the latter permitting the addition of four additional lists and two

EFFECTS OF PROLONGED LEARNING ON LEARNING

TABLE 3

MEASURES OF RETROACTIVE AND PROACTIYE EFt:ECTS

179

Means of Saving Scores with 2 Retroactive Interpolations N.P.I. a 4 12 16 24 28 37 41 49

10 Ss 56.1 60.3 57.7 46.3 44.7 57.2 55.3 49.1

7 Ss 59.7 73.7 62.8 45.9 60.5 48.8 57.6 50.5

N.P.I. 53 61 65 74 78 86 90 Total

10 Ss 54.0 50.9 58.1 53.61

7 Ss 55.6 47.7 60.3 54.9 39.4 59.5 53.0 54.66

Means of Saving Scores with 9 Retroactive Interpolations N.P.I. 1 13 38 50 75 87 Tota l

10 Ss 46.5 41.8 55.8 56.3 50.11

7 Ss 31.6 31.2 50.7 62.6 60,6 40,8 46.35

Means of Saving Scores with 21 Retroactive Interpolations N.P.I. 14 51 Tota l

9 Ss 48.1 33.1 40.6

Means of Saving Scores with 32 Retroactive Interpolations N.P.I. 2 39 Total

9 Ss 56,5 49.8 53,2

a Number of Proact ive Lists.

additional recall lists for the "two" and "nine" interpolations, respectively.

An analysis of variance for each of the various sets of recall scores yielded no significant differences among the sets of means with the exception of the "nine" interpolation groups for seven Ss (F z 3.24, d ] - -

5/25, P ~ .05). Nor did an analysis of the grand means of the various recalls under the four conditions of retroactive interpolations yield a significant difference.

DISCUSSION

In very general terms, a statement of our findings is quite simple. A measure of paired- associate learning, after five hours of con- tinuous learning, shows no decrement in performance when compared with such measures in the first hour of learning. Stated other- wise, and on the assumption that this measure is a valid one of learning efficiency, hu- man Ss may be expected to maintain their efficiency as learners for periods up to 6 hours. The data further support the statement that retention of material which has been learned during a 6-hour learning se- quence shows no decrement as a function of cumulative effects of prior learning. Finally, when amount of material learned is considered

as a variable, again no evidence was obtained to indicate that efficiency of learning deterio- rates as a function of large amounts of prior materials learned.

Setting the limiting characteristics of these broad generalizations is, of course, necessary. A particular kind of learning material and learning task was used--paired associate learning of Russian-English vocabulary. Hence, we could only make shaky inferences about learning in tasks which, for example, produce high intratask and cumulative trans- fer (e.g., problem solving tasks), or tasks with high effort components (e.g., motor-skill tasks), or tasks which have intrinsic motivation (e.g., coherently organized material). Further, it must be noted that the rate of learning was extrinsically paced and as such, the amount of learning input could not, for example, be controlled by motivational factors as would be the case in a more "naturalistic" setting. Finally, the task of the S was that of acquiring a response in the presence of a stimulus for relatively short-run reproduction in contrast to organizing material for long- time retention.

Given, then, the restrictive nature of the experimental situation, 'these results would seem to reflect the basic "capacity" of hu-

180 WEBB

man Ss in acquiring associations after considerable amounts of similar material. This process may be considered at least a significant part or element in all of the more complex processes suggested above that were not tested.

In both the analysis of total learning over six hours and the analyses related to learning of 72 lists, a generally common phenomenon was noted for the groups, viz., an increase in proficiency of learning from the first to the second sixths of learning and an increase in proficiency in the fifth and/or sixth, or last, sixths of learning. The decrease in proficiency in the middle period of learning is substan- tiated by the blocking data. The nonlinear nature of the curve of 6 hours of learning is emphasized and supported by a significant quadratic test.

An initial rise in performance can be inter- preted as a prolonged "learning to learn" effect which has been well documented in the literature over generally less extensive learning tasks. A clearcut picture of this effect over less extensive material (and presented one list per day rather than in one session) is seen in Ward's data resulting from the learning of 16 lists, 12 items in length (Ward, 1937). This "learning to learn" is, of course, quite different from the initial "adjustive" learning occurring between the first list and the remaining lists which was quite apparent in our data (mean trials for List 1 ~ 17.9 trials; List 2 ~ 11.2 trials; List 3 ~ 11.9 for the 38 Ss validly completing two lists).

The decrease in proficiency fulfilled our original expectations about prolonged learning. We had assumed that prolongation of the learning process within the same session with material learned only to a criterion of single reproduction would result in increasing proactive interference and certainly decrements in motivation which would lead to lower performance measures. We would at- tribute our obtained decrements to such factors.

The most surprising, and perhaps the most significant, aspect of our data is seen in the efficient level of performance demonstrated in the fifth and sixth hours of learning and in

the last sixths of considerable amounts of material.

The most obvious interpretation of this increase in effectiveness is that the rise in the later part of learning is an "end spur t " - -a tendency which has been often noted. Three factors would argue against this explanation. First, although the Ss knew they were to learn for at least six hours, they were not permitted to have watches. Although they may have guessed that nearly six hours were up, our anecdotal reports from the Ss indicated that their time estimates were quite distorted. Many Ss began to ask about "how much longer" (with the implication of "certainly not much longer") after as little as one or two hours; on the other hand, after they had become involved in the task, fre- quent expressions of surprise occurred when the last trial was terminated. Secondly, this "end spurt" would have little resemblance to the more classical "end spurts" which typically operate in the last few trials of tasks. This "end spurt" would have to be conceived of as lasting over one or two hours. Finally, and perhaps most critically, the data on amount of material (72-list data) could not be ex- plained in this way at all since for some of the Ss this point occurred as early as two hours after learning began, whereas for others this was occurring in the sixth hour of learning. For these data, then, the "end spurt" could not be present for more than a few Ss.

Our preferred interpretation of this effect stems primarily from the observation of the Ss in the later part of learning. A "mechanization" of learning seemed to be taking place. A "typical" S's behavior would be somewhat as follows in the later part of learning: While grumbling at the E about the length of the time he had been at the task, or asking, "How long is this - - experiment going to go on?" he may be lighting a cigarette or stand- ing up from the chair. Yet he would glance at the stimulus word and apparently in- voluntarily give a response word and glance at the correct response word. He then may comment on the English word or the Russian word as to its associated meaning to him. Then a glance at the next stimulus word

EFEECTS OF PROLONGED LEARNING ON LEARNING 181

with a response to it with a response word. Other Ss would interject varying kinds of schema such as placing the response words ideationally on the screen with three at the top and three at the bottom, or concentrate on never missing, for example, the fourth word. Yet within the schema (which would typically last only for a few lists) the stimulus word would seem to be "picked off" when it appeared and a response word elicited with little hesitation. In essence, learning seemed to proceed independently of motivation or irrelevant responses, such as side comments, or stretching, or cigarette lighting, or self- induced schema, or, perhaps more critically, prior list interference. In short, it seemed that an intrinsically autonomous process had de- veloped and was operating in a mechanical fashion (hence the term "mechanization").

Although this tendency for learning to become routinized was unexpected, it is not a new observation nor problem. Hunter (1937) reviewed and discussed the routinizing of learning in a vice-presidential address before Section I of the American Association for the Advancement of Science. In the early 1900's, Woodworth had noted that continued learning may result in a "mechanization of drives" to the extent that a person continues to per- form in absence of an apparent motivation.

I t is not possible directly to compare our data with earlier findings of learning of extensive material. As noted previously, these experhnents took the form of distributed practice (24-hour intervals) with similar units (e.g., Ward, 1937), or increased within task material (e.g., Lyon, 1917). I t is interesting to note that Deese's replotting of the data of Lyon, using increasing material and single session practice, yields results similar to our data (Deese, 1958). This replotting of the N of repetitions required per syllable up to 200 showed an increasing interference followed by a sharp increase in efficiency of learning per syllable, suggesting the development of learning procedures with increased practice which lead to a minimiza- tion of interference.

A discussion of the recall data is more difficult. Because of list heterogeneity, a mean- ingful analysis of the Group I data is almost

impossible. As a result we have useful data on a somewhat limited number of cases.

I t would seem unfortunate and fortunate that there was a general lack of significance among the recall means as a function of prior learning. I t is unfortunate in that the data represent some of the most extended data on proaction within one learning session presently available and a significant effect would perhaps clarify the role of proactive inhibition in recall. On the other hand, it is perhaps fortunate in that the data present considerable problems in interpretation.

In regard to the prior learning effects on recall in the one condition where a hint of a trend was present (recall after nine RI lists), the effects were opposite to those expected, i.e., there was a decreasing proactive effect. The two conditions having large amounts of RI showed insignificant effects in the predicted direction. In the "two" RI condition, where the most measurements were obtained, the data on ten Ss would yield a trend to only the most imaginative, e.g., recalI after sixty-six proacfive lists was more than all other conditions except one; or again, the average saving in the five recalls after forty or more proactive lists was approximately 53%, whereas the saving in five recalls with less than forty proactive lists was approximately 54%. The most appropriate conclusion would seem to be that no marked proactive interference effects were obtained.

Similar statements apply to the retroactive interpolative effects. Only recall after 21 retroactive interpolations indicated a considerable RI effect, and this was not supported by the 32 RI condition.

Several interpretations may account for the general lack of significant RI or PI effects. The savings method is known to be a relatively insensitive measure of these effects. Or the relatively short time intervals between recalls may well have been too short for the slowly developing PI to become effective. Further, an interaction between RI and PI may have obscured this effect. Finally, it may be that the lack of effect is a real one brought about by the Ss, as in the case of learning, developing learning procedures which minimized interference effects. A mini-

182 WEBB

real conclusion which can be drawn is that the Ss were not maintaining their efficiency of learning by learning to forget their previous learning.

SUM/VfARY

The Ss in this experiment were presented six English-Russian pairs to learn by the anticipation method to a criterion of one correct reproduction. The presentation rate was 2 sec. After a list was learned to criterion a new list was immediately introduced and learned to the same criterion. This was followed by further lists. Recall measures were interspersed after every third list with varying amounts of interpolation of lists between learning and recall measures. Learning con- t inued for six hours without interruption, or unti l 111 learning and recall lists had been completed. Two list orders were used to minimize list differences. Eighteen Ss learned one list order, 12 another order.

The data indicate that learning and recall did not decrease in proficiency after six hours or after 72 lists. There was some evidence of decremental effects in mid-learning. Late learning seemed to be characterized by a "mechanization" of the learning process in which acquisition became automatized.

REFERENCES

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BINET, A., AND HENRI, V. La m~mcire des mots. Ann. Psychol., 1894, 1, 1-23.

BgcI(, C. D., AND OT~ERS. Dictionary o] selected synonyms in the principal Indo-European languages; a contribution to the history o] ideas. Chicago: Univer. of Chicago Press, 1949.

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EBBIIgOI-IAUS, H. Memory: a contribution to experimental psychology (Trans. by H. A. Ruger and C. E. Bussenius). New York: Bureau of Publica- tions, Teachers College, Columbia Univer., 1913.

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LTJH, C. W. The conditions of retention. Psychol. Monogr., 1922, 31, No. 3.

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NEV~ANN, E. (Data cited in Lyon reference without reference to original article.)

UNDERWOOD, •. J. Interference and forgetting. Psy- chol. Rev., 1957, 64, No. 1.

WARD, L. B. Reminiscence and rote learning. Psychol. Monogr., 1937, 49, No. 4.

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(Received June 8, 1962)

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