1897.] Psychology. 171 
to a certain time of exposure the broader slit gave an effect of about 
double the brightness of the other. This was taken as the time re- 
quired for the maximal effect in the larger slit. When the time of 
swing was further lengthened this difference in intensity diminished and 
finally disappeared. Mr. Lough drew a parallel between the intensity 
Series and the scale of muscular sensations, though he was inclined to 
regard the latter as more than a mere intensity series. 
Prof. G. A. Tawney reported some experiments on the effect of prac- 
tice upon the tactual double point threshold, and the so-called ‘ Vex- 
irfehler” Asa rule he found that any reduction of the threshold was 
accompanied by an increase in the number of Vexirfehler. His expe- 
riences with different subjects indicated their division into three 
distinct classes. In some subjects there was a large reduction of the 
threshold as a result of practice, with a corresponding increase of Vex- 
irfehler; this reduction of the threshold was not confined to the regions 
actually practiced upon nor to their symmetrical points, but there was 
found to be a sympathetic reduction all over the body. In other sub- 
jects there were few Vexirfehler and only slight reductions of the 
threshold from practice. In others many Vexirfehler occurred from 
the very beginning, so that it was difficult to obtain any reliable value 
for the threshold. Suggestion was found to play an important rôle in 
every instance, and the results varied greatly according to the degree 
in which the subject was instructed beforehand as to the purpose of 
the experiment; where any suggestion was carefully avoided no real 
reduction of the threshold occurred; some of the subjects to whom no 
intimation of the nature of the problem was given, failed to get any 
Vexirfehler at all. The whole phenomenon of threshold reduction and 
Vexirfehler thus seemed to require a psychological rather than a phy- 
siological explanation. 
Mr. A. L. Lewis, introduced by Prof. Witmer, read a paper on 
“Comparison of the Times of Simple Reactions and of Free Arm 
Movements in Different Classes of Persons.” His subjects were white 
men and women, Indians and negroes, both of the latter classes being 
males, The instrument used was the Hipp chronoscope, which was 
tested before and after every series, giving constant and variable errors 
of only 1¢ each. Reactions on sound showed the order, from the short- 
est time upward, to be Indians, white men, negroes, women ; the first 
two classes were between 100s and 110s, the last two were between 
150s and 160s. For visual stimuli the white men gave a reaction time 
Somewhat shorter than the Indians; the time for free arm movemen 
