ing at all. Standing opposite the subject, I tried to
guess at the mental content of the person's mind, on the basis of
expressive movements. Sometimes I reacted by shaking or nodding the
head, etc., just as Hans had done, but as a rule I was content to say
the word which I thought the subject had in mind. With twelve subjects
(a total of 350 tests) I made an average of 73% correct responses, and
in the more favorable cases I attained even 90 to 100% correct
responses. Very slight involuntary movements of the head and eyes, which
showed but little individual variation, and always occurred when the
subject began to fix upon the concept, were the signs which I used as
cues. As in the case of the movements expressive of the release of
tension, which I discussed above, these movements, too, occurred without
the subject being aware of them, (except in those rare cases in which
they had once or twice been especially pronounced). Indeed, it was very
difficult and in some cases almost impossible for those persons whom I
had initiated into the secret, to inhibit them voluntarily. "Up" and
"down", "right" and "left", were expressed by movements of head or eye
in those directions, "forward" by a forward movement of the head, "back"
by a corresponding movement. "Yes" was accompanied by a slight nod of
the head; "no" by two to four rapid turnings of the head to either
side.[N] "Zero" was expressed by a movement of the head describing an
oval in the air. Indeed, it was even possible to discover whether the
subject had conceived of a printed or a written zero, for the
characteristics of both were revealed in the head-movements. I was able
later to verify this graphically. With Ch. as subject, I made 70%
correct interpretations in a total of 20 tests; with von A. as subject,
72% in a total of 25 tests. And finally I was able to interpret the
signs without any errors at all. It was not absolutely necessary to look
directly at the subject's face. Even though I focussed a point quite to
one side, so that the image of the subject's face would fall upon a
peripheral portion of my retina, I still was able to make 89% correct
interpretations in a total of 20 tests.--This is not astonishing after
all, when we recall that the periphery of the retina possesses a
relatively high sensitivity for movement impressions, although its
chromatic sensitivity is very low.[O]

[Footnote N: It was Charles Darwin[7] who first pointed out that the
exp