combination of two illusions--a shrinking of the open space, on the
one hand, and a lengthening of the filled space on the other hand.
Binet says, in his studies on the well-known Müller-Lyer illusion,
that he believes the illusion, in its highest effects at any rate, to
be due to a double contrast illusion.

This distortion of contrasted distances I have found in more than one
case in this investigation--not only in the case of distances in which
there is a qualitative difference, but also in the case of two open
distances. In one experiment, in which open distances on the skin were
compared with optical point distances, a distance of 10 cm. was given
fifty times in connection with a distance of 15 cm., and fifty times
in connection with a distance of 5 cm. In the former instance the
distance of 10 cm. was underestimated, and in the other it was
overestimated.

The general conclusion of the entire investigation thus far may be
summed up in the statement: _Wherever the objective conditions are the
same in the two senses, the illusion exists in the same direction for
both sight and touch._


VI.


Thus far all of my experiments were made with _passive_ touch. I
intend now to pursue this problem of the relation between the
illusions of sight and touch into the region of _active_ touch. I have
yielded somewhat to the current fashion in thus separating the passive
from the active touch in this discussion. I have already said that I