1248 
TABLE IV. 
7, = rT 
Observers | Repent gen | Arithm. mean | Mean deviation Median 
| | 
| 6g 11.26 | 1.03 10.87 
M. | | | 
| 80 r 11.31 | 1.21 11.47 
| 
| | 86 1 13.44 | 1.40 12.95 
R. | | 
49 r 11.79 | 1.08 11.66 
| | 173 | 11.16 | 1.40 10.44 
D. 
| 110 7 9.86 | 1.39 | 9.71 
| | 
greater for the learning- than for the repetition-experiments; for M. 
they are almost equal. For learning as weil as for repeating a 
repetition requires on the average more time with I than with II. 
Only in the case of repeating does the average duration of a repetition 
for M. approximate to that of I. 
The following tables illustrate how the observers modified the 
rate of succession spontaneously according as they were getting more 
familiar with the material. For every series we divided the repetitions 
necessary to» learn the material by heart (learning and repetition) 
into three groups of successive repetitions. For each group we 
calculated the mean duration of its repetitions. A comparison of the 
time-values of each group shows the changes in the rate of succession 
in learning and repetition concurring with the greater familiarity 
on the part of the observer with the material to be impressed. It 
should be observed that, when the number of repetitions was not 
divisible by three, the first and the last group always contained the 
same number of repetitions which made the middle group longer or 
shorter by one repetition. Though the time of exposure of the 
syllables, as established by the mnemometer was always the same 
with II the observer had ample opportunity to lengthen or to shorten 
the duration of the repetitions to a certain extent, as he was at 
liberty to read the first and the last syllable of the series at any 
moment of the period during which they remained visible in the slit. 
So with II there may also be a tendency to shorten or to lengthen 
the duration of the repetitions as the learning-process advances. 
Apart from a few exceptions for D, the duration of the repeti- 
tions increases according as the observer is getting more familiar 
with the material to be impressed, in the learning- as well as in 
