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 Each double test consisted in this, that the separate series—each for itself—were first read attentively a given number of times (after frequently repeated readings they were recited by heart instead of read), and that 24 hours later I relearned up to the point of first possible reproduction the series thus impressed and then in part forgotten. The first reading was repeated 8, 16, 24, 32, 42, 53, or 64 times.

An increase of the readings used for the first learning beyond 64 repetitions proved impracticable, at least for six series of this length. For with this number each test requires about ¾ of an hour, and toward the end of this time exhaustion, headache, and other symptoms were often felt which would have complicated the complicated of the test if the number of repetitions had been increased.

The tests were equally divided among the seven numbers of repetitions investigated so that to each of them were allotted 10 double tests. The results were as follows for the six series of a single test taken together and without subtraction of the time used for reciting.

After a preceding study of the series by means of “x” repetitions, they were learned 24 hours later with an expenditure of “y” seconds.

The preceding table of numbers gives the times actually used in learning by heart the series studied 24 hours previously. Since we are interested not so much in the times used as the times saved we must know how long it would have taken to learn by heart the same series if no previous study had been made. In the case of the series which were repeated 42, 53, and 64 times,