Experiments with No. 3
No. 3 was kept in a cage not half so big as those of 1 and 2. Perhaps because of the hindrance this fact offered to forming the habit of reacting in some definite way to ‘yes’ signals, perhaps because of the fact that I did not try hand movements as signals, there was no successful discrimination by No. 3 of the yellow from the black diamond or of a card with YES from a card with a circle on it. I tried climbing up to a particular spot as the response to the ‘yes’ signal and staying still as the response to the ‘no’ signal. I also tried instead of the latter a different act, in which case the animal was fed after both signals but in different places. In the latter case No. 3 made some progress, but for practical reasons I postponed experiments with him. Circumstances have made it necessary to postpone such experiments indefinitely.
Permanence of the Ability to Discriminate
No. 1 and No. 2 were tried again after intervals of 33 to 48 days. The results of these trials are shown in [Fig. 32]. Here every millimeter along the base line represents one trial with the ‘no’ signal (the ‘yes’ signals were practically perfect), and failure is represented by a column 10 mm. high while success is represented by the absence of any column. Thus the first record reads, “No. 1 with signal 104 after 40 days made 5 failures, then 2 successes, then 1 failure, then 1 success, then 3 failures, then 1 success, then 1 failure, then 3 successes, then 1 failure, then 10 successes.” The third record (106; 40 days) reads, “perfect success in ten trials.”
Fig. 32.
Discussion of Results
The results of all these discrimination experiments emphasize the rapidity of formation of associations amongst the monkeys, which appeared in their behavior toward the mechanisms. The suddenness of the change in many cases is immediately suggestive of human performances. If all the records were like c, f, h, i, j, k, l, m, B, E, and memory trials 103, A, B, and C, one would have to credit the animals with either marvelous rapidity in forming associations of the purely animal sort or concede that from all the objective evidence at hand they were shown to learn as human beings would. One would have to suppose that they had clear ideas of the signals and clean-cut associations with those ideas. The other records check such a conclusion.
In studying the figures we should remember that occasional mistakes, say 1 in 10 trials, are probably not significant of incomplete learning but of inattention or of precipitate action before the shutter had fairly exposed the card. We must not expect that a monkey who totally fails to discriminate will always respond wrongly to the ‘no’ signal, or that a monkey who has come to discriminate perfectly will always respond rightly. A sudden drop from an average high level of error to an average low level will signify sudden learning. Where the failure was on the first trial of a series a few hours or a day removed from the last series, I have generally represented the fact not by a column 1 mm. high and 1 mm. broad, but by a single 10 mm. perpendicular. See i and A. Such cases represent probably the failure of the animal to keep his learning permanent rather than any general inability to discriminate.
K was to some extent a memory trial of d (after over half a year).