instance, that the æsthetic processes have attracted our attention in
an especially high degree. But even if we abstract from their
important relation to the motor functions, we have good reasons for
turning to them, as the æsthetic feelings are of all feeling processes
decidedly those which can be produced in the laboratory most purely;
their disinterested character makes them more satisfactory for
experimental study than any other feelings.

Another group of researches which predominates in our laboratory is
that on comparative psychology. Three rooms of the laboratory are
reserved for psychological experiments on animals, under the special
charge of Dr. Yerkes. The work is strictly psychological, not
vivisectional; and it is our special purpose to bring animal
psychology more in contact with those methods which have found their
development in the laboratories for human psychology. The use of the
reaction-time method for the study of the frog, as described in the
fifteenth paper, may stand as a typical illustration of our aim.

All the work of this volume has been done by well-trained
post-graduate students, and, above all, such advanced students were
not only the experimenters but also the only subjects. It is the rule
of the laboratory that everyone who carries on a special research has
to be a subject in several other investigations. The reporting
experimenters take the responsibility for the theoretical views which
they express. While I have proposed the subjects and methods for all
the investigations, and while I can take the responsibility for the
experiments which were carried on under my daily supervision, I have
left fullest freedom to the authors in the expression of their views.
My own views and my own conclusions from the experiments would not
seldom be in contradiction with theirs, as the authors are sometimes