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 constant, the saving in work which results from these repetitions increases accordingly for a while proportional to their number. Gradually the effect becomes less; and finally, when the series has become so firmly fixed that it can be repeated almost spontaneously after 24 hours, the effect is shown to be decidedly less. The results of the and the present chapter, as far as can be seen, support each other.

Nevertheless, there is a noteworthy distinction to which I call attention. We found above that six 12-syllable series, which had been learned at a given time with an average of 410 repetitions, could be learned by heart at the end of 24 hours with, on the average, 41 repetitions. For a single 12-syllable series, accordingly, 68 immediately successive repetitions had the effect of making possible an errorless recital on the following day after 7 repetitions. In the present research with distribution of the repetitions over several days the same effect appears on the fourth day: 9 12-syllable series were learned by heart with 56 repetitions. Each series, therefore, was learned with about 6 repetitions. But the number of repetitions which were necessary for the production of this effect in the case of the nine series amounted to only 158+109+75=342. For a single series, therefore, the number was 38. For the relearning of a 12-syllable series at a definite time, accordingly, 38 repetitions, distributed in a certain way over the three preceding days, had just as favorable an effect as 68 repetitions made on the day just previous. Even if one makes very great concessions to the uncertainty of numbers based on so few researches, the difference is large enough to be significant. It makes the assumption probable that with any considerable number of repetitions a suitable distribution of them over a space of time is decidedly more advantageous than the massing of them at a single time.

With this result, found here for only very limited conditions, the method naturally employed in practice agrees. The school-boy doesn’t force himself to learn his vocabularies and rules altogether at night, but knows that he must impress them again in the morning. A teacher distributes his class lesson not indifferently over the period at his disposal, but reserves in advance a part of it for one or more reviews.