space, in the filled half the sensations were largely of external
origin, while in the open half they were of internal origin. The
result was that the spaces filled with sensations of internal origin
were always overestimated.

The failure to recognize the importance of these inwardly initiated
sensations is the chief defect in Dresslar's reasoning. He has
endeavored to make our judgments in the illusion in question depend
entirely on the sensations of external origin. He insists also that
the illusion varies according to the variations in quantity of these
external sensations. Now my experiments have shown, I think, very
clearly that it is not the numerical or quantitative extent of the
objective sensations which disturbs the judgment of distance, but the
sensation of inner origin which we set over against these outer
sensations. The piece of plush, because of the disagreeable sensations
which it gives, is judged shorter than the space filled with closely
crowded tacks. Dresslar seems to have overlooked entirely the fact
that the feelings and emotions can be sources of illusions in the
amount of movement, and hence in our judgments of space. The
importance of this element has been pointed out by Münsterberg[19] in
his studies of movement.

[18] Delabarre, E.B., 'Ueber Bewegungsempfindungen,' Inaug.
Dissert., Freiburg, 1891.

[19] Münsterberg, H., 'Beiträge zur Experimentellen Psychol.,'
Freiburg i. B., 1892, Heft 4.

Dresslar says again, "The explanations heretofore given, wholly based
on the differences in the time the eye uses in passing over the two