there is general agreement that a distribution of periods of study gives the best results. Ebbinghaus found, in committing nonsense-syllables to memory, that thirty-eight repetitions distributed over three days produced the same results as sixty-eight repetitions at a single sitting. Starch experimented with fortytwo students. They were divided into four groups, one of which worked ten minutes at a time twice a day for six days; the second group twenty minutes at a time once a day for six days; the third worked forty minutes every other day for six days; the fourth did the entire task at one sitting of two hours. The results showed a great advantage for the shorter, more widely distributed periods. The two-hour period of work at one sitting was a bad fourth. The advantageous periods of work in this experiment seem short, but the occupation consisted in associating numbers with letters, a task which would quickly cause fatigue. Jost carried these experiments much further than any of the other investigators and proved that neither fatigue nor inattention explains the advantage of this distribution of time. Having eliminated these two factors, he undertook to determine the best arrangement of periods of work, and he found that twenty-four repetitions, distributed over twelve days with two repetitions a day, gave better results than less distributed periods. He inclines to an even more extended distribution. If we accept Jost's view, that the Journal of Psychology, vol. 24, p. 580. Hermann Ebbinghaus, Memory, p. 89; Grundzüge der Psychologie, third edition, vol. 1, pp. 657 ff. John Bigham, Psychological Review, vol. 1, p. 453. Alfred Binet, L'Année psychologique, vol. 10, p. 116. W. F. Dearborn, Journal of Educational Psychology, vol. 1, p. 273. Adolf Jost, Zeitschrift f. Psychologie, vol. 14, p. 436. E. A. Kirkpatrick and Abbie F. Munn, op. cit. J. H. Leuba and Winnefred Hyde, Psychological Review, vol. 12, p. 351. O. Lipmann, op. cit. E. Meumann, Psychology of Learning, pp. 265 f. G. E. Müller and A. Pilzecker, op. cit. Max Offner, op. cit. Nellie L. Perkins, British Journal of Psychology, vol. 7, p. 253. Adolf Pohlmann, op. cit., pp. 82 f. Fritz Reuther, op. cit. D. Starch, op. cit. advantage of distributed practice and study1 lies in the greater effectiveness of old associates, Miss Perkins' results2 "indicate that this process of consolidation continues for at least forty-eight hours, and still longer if four or more readings are made on each day" [of practice]. Putting these investigations into general terms, the experiments show conclusively that an extensive distribution of study periods for a given piece of work is advantageous both for rapidity of learning and for permanent retention. The period favorable for one sitting and the length of intervening time will depend, among other things, upon the nature of the material and the difficulty of the task, with its accompanying fatigue. The economy of distributed study, instead of finishing what one is engaged upon and then dropping it, may then be considered established. Jost next sought to determine why it is more advantageous to spread study or practice over several days instead of finishing the work at one sitting. He came to the conclusion that older associations-those which were established earlier are more easily renewed than the more recent ones. This explanation, however, still leaves the question Why? unanswered. Some find the explanation in the effect of activity upon the nutrition of the organ exercised,3 and in the dropping out of interfering associations. This would be a satisfactory explanation were considerable practice always involved. But the same advantage of distributed study is observed when the selection is read but once each time. A "setting" or "fixing" of associations, on the other hand, apparently satisfies conditions. Those that are older have had more time in which to become "fixed." Since it is difficult to understand in what this "fixing" consists, unless it be the result of cere 2 1 Jost experimented only upon learning and relearning, i. e., memory. Op. cit. Physiological Psychology, by G. T. Ladd and R. S. Woodworth, p. 581. bral nervous activity, we seem at present compelled to take this view. This explanation of the "setting" of associations during periods of rest is also indicated by experiments in relearning skilful acts after a long interval without practice. The writer at one time acquired considerable proficiency in tossing two balls with one hand, one ball being caught and thrown while the other was in the air. More than six years later he again tested himself in this feat. In eleven days he greatly exceeded the skill which he had acquired six years before after forty-two days of arduous practice. The following curves show the progress during the original learning process, and during the test in relearning the same feat six years or more later. The curve of relearning is on the left. The rate of progress is shown at the left of the perpendiculars, and the days required in each case are indicated under the base line.1 The practice in which the skill was first gained was finished six years before this memory test was made. After the conclusion of the first investigation there were five monthly tests of the effect of intermission of practice, and one memory test two years later. With these exceptions there had been no practice during the six years. The writer has also determined the effect of intermission of practice on the typewriter.2 In this instance, the memory test was made more than two years after the close of the first experiments by which a certain degree of skill was attained. During the intervening two years he had not used any style of typewriter. The original investigation covered a period of fifty days, while in the memory test, two years later, only eleven days were required to reach the degree of proficiency with which the original investigation closed. This curve is reproduced from the Psychological Bulletin, vol. 7, p. 17. The remarkably short time needed in both of these investigations to regain the former skill, after the long interval without practice, shows the persistence of neuromuscular memory. A still more significant fact, however, is disclosed by the curves for ball-tossing given above. It will be observed that in eleven days, after six years of cessation of practice, the experimenter acquired much greater skill than that with which he closed his experiments of forty-two days, six years earlier. It is clear that the effects of activity upon the nutrition of the organ exercised and the dropping out of interfering associations do not account for the persistence and rapid improvement of skill after such long periods of inactivity. The astonishingly rapid gain in skill in ball-tossing beyond that originally acquired indicates not only a "fixing" of nervous and muscular associations, but also, during the long interval, some sort of integrative nervous activity by which the skill was further improved. At present there is no other tenable explanation. Batson, in his investigation,1 also observed improvement in skill during intervals of no practice. "After a long rest period," he says, "the subject is found to be in a condition to improve very rapidly. In some cases the results show that they have actually gained power during the rest period." The matter of "rest periods" has wide application. Jost's investigations, as well as the others to which reference has just been made, emphasize the value of repetitions, but always with an interval between them. A book, a legal opinion, an investigation in medicine or in science, which one wishes to remember, should be read again, but not at once. It is always important, however, that the meaning be as clear as possible in the first reading, because that gives the memory a freer field; and, when it is a matter of elaboration rather than of memory alone, the reconstruction of the thoughts, as a result of cerebral proc1 Op. cit. |