correctly, and not only to distinguish four from three but to
distinguish four from more than four. Hence five, six, seven, and
eight at a time were often given. When the subject had learned to do
this fairly well the plan was to give him one, two, three, and four in
order, then to double the weight of the four and give them again to
see if he would interpret the additional weight as increase in number.
This was done and the results were entirely negative. The subjects
either noticed no difference at all or else merely noticed that the
second four were a little more distinct than the first.

The next step was to give a number of light contacts to be compared
with the same number of heavy ones--the subject, not trying to tell
the exact number but only which group contained the greater number. A
difference was sometimes noticed, and the subject, thinking that the
only variations possible were variations of number and position, often
interpreted the difference as difference in number; but the light
weights were as often called more as were the heavy ones.

So far as the primary object of this part of the experiment is
concerned the results are negative, but incidentally the process of
training brought out some facts of a more positive nature. It was
early noticed that some groups of four were much more readily
recognized than others, and that some of them were either judged
correctly or underestimated while others were either judged correctly
or overestimated. For convenience the fingers were indicated by the
letters _A B C D_, _A_ being the index finger. The thumb was not used.
Two weights were over each finger. The one near the base was called 1,
the one toward the end 2. Thus _A12 B1 C2_ means two contacts on the
index finger, one near the base of the second finger, and one near the
end of the third finger. The possible arrangements of four may be