The same results were obtained from other subjects. In my experiments
on the illusion for passive touch, I pointed out that it is unsafe to
draw any conclusion from a judgment of comparison between open and
filled cutaneous spaces, unless we had previously determined what
might be called a standard judgment of comparison between two open
spaces. The parts of our muscular space are quite as unsymmetrical as
the parts of our skin space. The difficulties arising from this lack
of symmetry can best be eliminated by introducing at frequent
intervals judgments on two open spaces. As I shall try to show later,
the psychological character of the judgment is entirely changed by
reversing the order in which the spaces are presented, and we cannot
in this way eliminate the errors due to fluctuations of the attention.

The apparatus which I used in these first experiments possesses
several manifest advantages. Chief among these was the rapidity with
which large numbers of judgments could be gathered and automatically
recorded. Then, in long distances, when the open space was presented
first, the subject found no difficulty in striking the first point of
the filled space. Dresslar mentioned this as one reason why in his
experiments he could not safely use long distances. His subjects
complained of an anxious straining of the attention in their efforts
to meet the first point of the filled space.

There are two defects manifest in this apparatus. In the first place,
the other tactual sensations that arise from contact with the thimble
and from the friction with the carrier moving along the sliding rod
cannot be disregarded as unimportant factors in the judgments.
Secondly, there is obviously a difference between a judgment that is
made by the subject's stopping when he reaches a point which seems to