[20] The crude experiments reported in this and the preceding paragraphs were not made to test the presence of color vision proper, that is, of differentiation of two colors of the same brightness, but only to ascertain how chicks reacted to ordinary colored objects. It was, however, almost certain from the relative frequency of the reactions that the intensity factor was not the cause of the response. For example, if it had been, black on white and yellow on black should have been pecked at oftener. [21] This chapter appeared originally in the _American Naturalist_, Vol. XXXIII, No. 396. [22] This chapter appeared originally as Monograph Supplement No. 15 to the _Psychological Review_. [23] Pp. 20 to 155 of this volume. [24] _American Journal of Psychology_, Vol. X, pp. 256-279; Vol. XI, pp. 80-100, 131-165; Vol. XII, pp. 206-239. [25] Practically a memory trial of CC, done January 21, 1900. [26] Did it by pulling door and thus shaking lever. [27] Practically a memory trial of SS. [28] Did it by pulling door and biting wire. [29] This, I regret, was not done [E. L. T., 1911]. [30] The acts and the number of chances to see me do each and the results were as follows; details can be found on the table on page 226. F = failed after tuition. No. 1.—MM 21 F Theta 5 F QQ 10 F RR 4 F W 9 did in .22 Delta 15 F Epsilon 40 F QQ (f) 15 F QQ (c) 1 did in 2.20 No. 3.—Theta 25 did in 3.00. QQ 40 F Gamma 30 F Epsilon 25 F QQ (ff) 5 F QQ (c) 20 F, did in 1.30, F, 5 F, 5 F QQ (e) 5 F, did in 2.00 [31] He did push it once with his nose. [32] I inadvertently pulled the nail out in one of five cases when I was fingering it to see if attracting his attention to it would lead to the act. [33] Not significant. Due to inattention. Was temporary. [34] Pulled wire and door. [35] Pushed with head by chance. [36] Reached in at 9:30 and took out the banana, which I replaced. [37] Did by constant pulling at the door. [38] Did touch nail four times. [39] Did by pulling hard on wire (not loop); the loop got loose from nail. [40] Did by pulling at the door till the bar was worked around. [41] The ‘say,’ may be replaced by some bodily attitude, facial expression, or other verbal formula that identifies the situation as one to be responded to by speech. [42] This would, of course, result from a well-known corollary of the laws of habit. [43] In _Essays Philosophical and Psychological in Honor of William James_, pp. 591-599. [44] Professor Smith’s own experiments illustrate this. [45] Biological Lectures from the Marine Biological Laboratory of Woods Holl, 1898, p. 323 ff. [46] This chapter appeared originally in the _Popular Science Monthly_, Nov., 1901. INDEX Abstraction, 120. _See also_ Reasoning.