a radical error or oversight. I may say
here, parenthetically, that I see no reason why experimental
psychologists should so often be reluctant to admit that they begin
certain investigations with preconceptions in favor of the theory
which they ultimately defend by the results of their experiments. The
conclusions of a critical research are in no wise vitiated because
those conclusions were the working hypotheses with which the
investigator entered upon his inquiry. I say frankly, therefore, that
although my experiments developed many surprises as they advanced, I
began them in the belief that the optical illusions are not reversed
for touch. The uniformity of the law of sense perception is prejudiced
if two senses, when affected by the same objective conditions, should
report to consciousness diametrically opposite interpretations of
these same objective facts. I may say at once, in advance of the
evidence upon which I base the assertion, that the belief with which I
began the experiments has been crystallized into a firm conviction,
namely, that neither the illusion for open or filled spaces, nor any
other optical illusion, is genuinely reversed for touch.

II.

I began my work on the problem in question by attempting to verify
with similar apparatus the results of some of the previous
investigations, in the hope of discovering just where the suspected
error lay. It is unnecessary for me to give in detail the results of
these preliminary series, which were quite in agreement with the
general results of Parrish's experiments. Distances of six centimeters
filled with points varying in number and position were, on the whole,
underestimated in comparison with equal distances without intermediate
point stimulations. So, too, the card with saw-toothed notches was
judged shorter than the card of equal length with all but the end
points cut out.

After this preliminary verification of the previous results, I was
convinced that to pass from these comparatively meager statistics,
gathered under limited conditions in a very special case, to the
general statement that the optical illusion is reversed in the field
of touch, is an altogether unwarranted procedure. When one reads the
summarized conclusions of these previous investigators, one finds it
there assumed or even openly asserted that the objective conditions of
the tactual illusion are precisely the same as those of the optical
illusion. But I contend that it is n