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natural and the experimental method the duration of every repetition, 
the time relation between the successive terms of one series, and its 
modification with the progress of the process of learning ete. 
The determination of the time required for every repetition and 
for the whole learning-process involved some difficulty as our voice- 
key, though it indicated distinctly the moment when the observer 
started the first syllable of a series, did not precisely report the 
moment when the reading of the last syllable was completed. 
However, we have ignored this source of experimental error in our 
calculations, seeing that the moment at which the last syllable is 
begun is easy of determination and only a minimal time (at the 
most 0,2 sec.) is required to pronounce a syllable consisting of two 
consonants with a vowel or a dipbthong between them. This may 
the more readily be done since it equally affects the time-values in 
both groups (I and II). 
In the experiments of Group II we had to look out for the 
moment the first syllable appeared in the slit as it need not coincide 
with the moment when the observer reads it. We, therefore, fitted 
to one side of the drum of the mnemometer a button, which, 
whenever the drum had come round again to its starting point, came 
in contact with a spring. With this contact we made the appearance 
of the first syllable coincide. The breaking of the circuit brought 
about by the contact was registered by means of a marking magnet 
on the drum of a kymographion. 
If the observer supposed he knew the series, he said it by heart. 
In case he broke down the experimenter presented the rest of the 
series once more. Close upon the recitation the observer told how 
he had proceeded in learning the syllables, how he had grouped 
his material, what associative connections he had made between 
the syllables. 
Every day four series were committed to memory. Precisely 24 
hours later we ascertained by the saving-method how much of the 
impressed material of the previous day had stuck. Group I was 
gone through unintermittently; not before this was got through did 
we start the second group. 
The subjoined table shows the mean number of repetitions which 
the several observers required to learn a series by the natural- (I), 
and by the experimental (II) method. For each observer the first 
and the third horizontal row shows the results of the learning- 
experiments (/) of the first day; the second and the fourth those of 
the repetition-experiments (7) 24 hours later. Alongside of the arith- 
metical mean we also tabulated the mean deviation and the median, 
