The simple relation approximately realised in these numbers is evident: the number of repetitions used to impress the series (Column I) and the saving in work in 1earning the series 24 hours later as a result of such impression (Col. III) increase in the same fashion. Division of the amount of work saved by the corresponding number of repetitions gives as a quotient a practically constant value (Col. IV).
Consequently the results of the test may be summarised and formulated as follows: When nonsense series of 16 syllables each were impressed in memory to greater and greater degrees by means of attentive repetitions, the inner depth of impression in part resulting from the number of the repetitions increased, within certain limits, approximately proportionally to that number. This increase in depth was measured by the greater readiness with which these series were brought to the point of reproduction after 24 hours. The limits within which this relation was determined were on the one side, zero, and, on the other, about double the number of repetitions that on the average just sufficed for learning the series.
For six series taken together the after-effect of each repetition—i.e., the saving it brought about—amounted on the average to 12.7 seconds, consequently to 2.1 seconds for each single series. As the repetition of a series of 16 syllables in itself takes from 6.6 to 6.8 seconds, its after-effect 24 hours later amounts to a scant third of its own duration. In other words: for each three additional repetitions which I spent on a given day on the study of a series, I saved, in learning that series 24 hours later, on the average, approximately one repetition; and, within the limits stated, it did not matter how many repetitions altogether were spent on the memorisation of a series.
Whether the results found can claim any more general importance, or whether they hold good only for the single time of their actual occurrence, and even then give a false impression of a regularity not otherwise present, I cannot now decide. I have no direct control tests. Later, however, (chapter VIII, § 34) where results obtained in reference to quite a different problem agree with the present results, I can bring forward indirect evidence on this point. I am therefore inclined to
