I wanted to train him to perceive one, two, three and four contacts at
a time on the back of his hand, and that I would tell him always how
many I gave him until he learned to do it. When it came to three I
gave him two points near the knuckles and one toward the wrist and
told him that was three. Then I turned the instrument around and gave
him one point near the knuckles and two toward the wrist and told him
that was four. As soon as he was sure he distinguished all of the
points I stopped telling him and asked him to answer the number. I had
four subjects, and each one learned very soon to recognize the four
contacts when three were given in the manner mentioned above. I then
repeated the same thing on the left hand, except that I did not tell
him anything, but merely asked him to answer the number of contacts he
felt. In every case the idea of four was so firmly associated with
that particular kind of a sensation that it was still called four when
given on the hand which had not been trained. I gave each subject a
diagram of his hand and asked him to indicate the position of the
points when three were given and when four were given. This was done
without difficulty. Two subjects said they perceived the four contacts
more distinctly than the three, and two said they perceived the three
more distinctly than the four.

It seems very evident that the sensation produced by three contacts is
no more complex when interpreted as four than when interpreted as
three. If that is true, then it must also be evident that the
sensation produced by one contact is no more complex when interpreted
as two than when interpreted as one. The converse should also be true,
that the sensation produced by two contacts is no less complex when
interpreted as one than when interpreted as two. Difference in number
does not indicate difference in complexity. The sensation of four is
not made up of four sensations of one. It is a unit as much as the