Harvard Psychological Studies, Volume 2

by Unknown

FIG. 1. Labyrinth L. BB, box 6 in. high; E, entrance; F, feeding-place; a, b, c, and d, moveable partitions 6 in. apart; NN, edge of pigeon cage; D, observation screen. The lamps which illuminated the room hung directly above the apparatus.

In this labyrinth (Fig. 1) six animals were tested once daily for thirty days, and five of these again after two and six weeks, respectively. On entering the labyrinth with the partitions in place the first time, a bird started on its usual direct course toward the food-box; running against the first partition it made vigorous efforts to push through, flying at the wire and often clinging to it for a short time; some of these random movements eventually brought it to the left of the compartment, and thence, through the opening, into the second compartment, and so on through the others, until finally it reached the food by a series of fortunate accidents.[198] The same general reaction was shown in case of the next few tests, except that fewer and fewer useless movements were made, and that the right ones were carried out with greater and greater precision. Later the animal had no difficulty in reaching the food; it did not run against the partitions, enter the blind alley, nor display such general signs of uncertainty as pausing and looking about. The process of learning in this case was obviously one of "trial and error," or the selection of useful movements. From the mass of random movements constituting the reaction to the unfamiliar environment, only those which enabled the bird to reach the food were retained and improved; the others gradually disappeared until finally the path taken became the shortest one possible, and was entered upon and pursued without hesitation by each animal as soon as it was allowed to enter the labyrinth. The time required for the tests is given in Table I.

It will be seen at a glance that the absolute time required for reaching the food varied for the individuals (see especially the results given by different birds in the case of test 1), but that the several periods for any one bird were relatively similar to those for another; and also that the time was long at first, but rapidly shortened from test to test, thus showing a steady advance in the learning process. Various lapses occurred (for example, A, 8; C, 13; E, 10) after the habit had been fairly well fixed.

In tests 18-22 the time-shortening was due principally to quickening of movements which had already become well defined. The great importance of visual data is brought out by the abrupt lengthening of the periods in the case of tests 23-25, and 26-30, where the light intensities were decreased. The lengthening was roughly proportional to the change of illumination. In the relative darkness the birds had to re-acquire the habits. The same mistakes were made as at first (running against partitions, and into the blind alley), yet here, as before, there was a ready adjustment. That the food was out of sight, or at least very much less visible, probably made no difference, since it was found that the birds would readily go to the old place after both food and food-box had been removed. In order to exclude the light entirely without making their movements invisible to me, I blindfolded the birds by means of a thin black hood, comfortably adjusted over their eyes and top of head; as a result, none was able to make the course in twenty minutes. The first turn, however, was usually made naturally, perhaps because associated with certain non-visual sense-data (sound of the lifting door, and perhaps tactual impressions of the close entrance compartment, etc.). Rats[199] seem far less dependent upon visual data than do pigeons. The great permanence of the pigeons' habits is shown by comparing the periods for tests 31-3, given after two and six weeks of rest, respectively, with those for tests 18-22.

TABLE I. TIME REQUIRED TO REACH FOOD IN LABYRINTH L

Animals
Trials, 1 daily.			A	B	C	D	E	F	Average
			' "	' "	' "	' "	' "	' "	' "
1		1)	28:50	:59	42:20	49:04	22:13	4:04	24:35
		2)	7:22	:22	25:47	10:17	:48	2:02	7:46
		3)	1:18	:12	8:29	12:35	:12	1:41	4:05
		4)	:32	:21	10:51	1:26	:19	:52	2:24
		5)	:24	:28	2:36	2:18	:12	1:33	1:15
		6)	:25	:26	1:10	:55	:12	1:50	:50
		7)	:15	:24	:28	:32	:15	2:09	:41
		8)	1:05	:23	:33	1:19	:17	1:46	:54
		9)	:16	:24	:57	:58	:10	:26	:32
		10)	:24	:32	1:15	:51	2:12	:31	:58
		11)	:12	:21	1:40	:30	:17	:54	:39
		12)	:16	:32	:49	1:34	:22	1:18	:49
		13)	:13	:18	2:30	:18	:10	:42	:42
		14)	:29	:32	:27	:31	:25	:36	:30
		15)	1:00	:24	:30	:31	:12	:35	:32
		16)	:19	:52	1:10	:22	:17	:24	:34
		17)	:14	:14	:31	:39	:13	:57	:28
2		18)	:13	:09	:29	:13	:16	:29	:18
		19)	:10	:10	:36	:26	:07	:14	:17
		20)	:11	:15	:34	:17	:07	:10	:16
		21)	:13	:14	:34	:16	:09	:21	:18
		22)	:09	:16	:26	:14	:08	:11	:14
3		23)	:12	:42	1:29	:39	5:53	:13	1:31
		24)	:20	:17	1:31	:33	:15	:13	:31
		25)	:15	:24	:40	:28	:19	:20	:24
4		26)	1:21	16:29	1:22	13:54	3:51	1:36	6:26
		27)	3:36	4:45	:44	1:03	1:09	2:59	2:23
		28)	:51	1:24	:46	1:04	:56	1:09	1:02
		29)	:51	:41	1:10	:40	2:17	:11	:58
		30)	2:04	:18	:41	:14	:07	:19	:37
	5	31)	:08	:33	:25		:07	:07	:16
	6	32)	:09	:15	:20		:08	:31	:17

1: With 18-candle-power illumination of the room.

2: Same illumination; tests given after the animals had heard four other pigeons pecking in the labyrinth.