Harvard Psychological Studies, Volume 2

by Unknown

		Group 1													Group 2
Animals		13	37	41	42	44	33	4	9	43	46		Sum		21	27	31	36	38	52		Sum		Sum Total
Blue		12	9	21	30	18							90		23	2	24	13	37			99		189
White		28	31	19	10	22							110		17	38	16	27	3			101		211
Green		15			9		23	36	17				100		12	19	3	28	40			102		202
White		25			31		17	4	23				100		28	21	37	12				98		198
Yellow		20	10	31	28	19							108		17	11	28	37	35			128		236
White		20	30	9	12	21							92		23	29	12	3	5			72		164
Red		26			9		32	20	17				104		2	30	16	29	36			113		217
White		14			31		8	20	23				96		38	10	24	11	4			87		183
Black			24	27		12				27	26		116		15	18		26	25	5		89		205
White			16	13		28				13	14		84		25	22		14	15	35		111		195

In this table the colored lights are arranged in the order of the spectrum from blue to red. On the hypothesis that blue light has practically the same effect upon animal reactions as white light, while red is about the same as darkness, we might expect that the reactions would be about equally divided between the blue and the white, and that there would be a gradually increasing difference in number as we go down the table, reaching the maximum with the last pair, black-white. This, we see, however, is not quite the case. In both groups the white has a slightly larger number of reactions than the blue, while the pair green-white shows numbers more nearly equal. In the sum totals the yellow shows a greater preponderance over the white than any other color, and the black and white are very nearly equal. Group 1, it is true, shows a fairly regular ascending scale in reactions to the colored lights with the exception of the red, and the same might be said of group 2 if it were not for the very low number of reactions to the black and the exceptionally high showing of the yellow. On the whole, however, the differences are so small and the individual variations are so large that we can only conclude that for these conditions colored light has little or no effect on the reactions of the animals.

In the foregoing experiment the light came from a broad spiral coil inside the bulb of the lamp, and the distance from it to the edge of the glass was so small compared with the length of the box that there was no sharp dividing-line between the colored light and the white, but rather a wedge-shaped block of lessening saturation of the color, and this wedge, having the point toward the light, took up the whole of the box at the extreme farther end. Thus the imaginary central line dividing the white light from the colored departed farther and farther from the reality as the rear of the box was approached. To obviate this difficulty and to get a check on the previous work, the following series of experiments was undertaken.

b. Reactions to Vertical Colored Light. The same box was used as in the previous experiments, but the end was closed with a black cloth, and an electric light marked 32 c. but measuring only 22 c. was hung exactly over the middle of the box, 40 cm. from the bottom. By means of wires it was arranged that a plate of colored glass could be swung in such a manner that all of one half the box (the whole of one end) was illuminated with the desired color, while the other half was either left white or illuminated with another color. In this way there was a fairly sharp dividing-line between the two colors. The animals were observed at intervals of one minute for 40 minutes, and reset at the middle on the dividing-line every ten minutes as before. Table VII gives the results of the observations.

In this set of experiments it was possible to keep the groups intact except that in group 1 no. 13 had to be replaced by no. 46. If now we conceive the colors arranged in the order of the spectrum with black at one end and white at the other, and consider the black a lower stimulus than the white, we have the ascending series black, red, yellow, green, blue, white. Now since the animals have already been shown to be somewhat negatively phototactic, we should expect them to prefer a color of lower stimulus to one of higher. Turning to the sum totals in the table we find that the first color of each pair (which is always the lower stimulus) has the larger number of reactions in every case but one, the first pair of red-blue. As was stated above, it was impossible to secure colored light of the same intensity by means of the glass at our disposal, and in the present case the red was considerably brighter than the blue. Owing to the fact already mentioned that different intensities of white light seem to have no effect on the reactions it was thought that these differences in the intensities of the colored lights might be overlooked. Since the only thing that could be thought of to account for the anomalous behavior to the red-blue was this difference in intensity, another experiment was undertaken with the same animals under slightly different conditions. A glass aquarium about 40 cm. long by 20 cm. wide was covered with black cardboard and black cloth in such a manner that light could enter only through a space 5 cm. wide at the bottom of each end. Each of these ends was covered, the one with blue, the other with red glass, and 15 cm. from each end was placed an electric light marked 32 c. Later, however, it was found that one of these lamps measured 30 c. and the other 22 c. The red light was found to be much more intense to the eye than the blue, so the former was damped down with tissue paper until the two appeared to have the same intensity. The second pair of red-blue in Table VII gives the results of the observations under these conditions, and these are found to be in harmony with the rest of the table, i. e.,[236] the color giving the lower stimulus has the higher number of reactions.

TABLE VII. REACTIONS TO VERTICAL COLORED LIGHT

	Group 1								Group 2								Group 3
Animal no.	13	37	41	43	44		Sum		21	27	36	38	52		Sum		54	56	58	60	62		Sum	Sum Total
Blue	17	22	14	25	29		107		11	21	26	27	26		111		26	32	26	28	10		122	340
White	23	18	26	15	11		93		29	19	14	13	14		89		14	8	14	12	30		78	260
Green	17	26	11	21	29		104		21	27	30	7	26		111		29	31	26	10	9		105	320
White	23	14	29	19	11		96		19	13	10	33	14		89		11	9	14	30	31		95	280
Yellow	25	21	12	20	35		103		12	20	34	25	29		120		19	20	9	28	22		98	321
White	15	19	28	20	15		97		28	20	6	15	11		80		21	20	31	12	18		102	279
Red	37	33	23	22	28		143		21	30	30	33	22		136		32	37	26	33	28		156	435
White	3	7	17	18	12		57		19	10	10	7	18		64		8	3	14	7	12		44	165
Black	23	20	1	28	34		106		9	12	25	40	32		112		25	32	18	34	16		125	343
White	17	20	39	12	6		94		31	28	15		14		88		15	8	22	6	24		75	257
Black	20	15	13	27	37		112		16	11	16	27	24		94		36	40	18	29	29		152	358
Red	20	25	27	13	3		88		24	29	24	13	16		106		4		22	11	11		48	242
Black	20[236]	25	26	20	32		123		22	15	39	40	32		148		33	22	34	34	11		134	405
Blue	20	15	14	20	8		77		18	25	1		8		52		7	18	6	6	29		66	195
Red	25	17	28	18	8		96		3	15	21	28	20		87		21	13	15	14	28		91	274
Blue	15	23	12	22	32		104		37	25	19	12	20		113		19	27	25	26	12		109	316
Red[237]	21	27	22	10	36		116		13	40	24	21	28		126		22	25	18	21	16		102	344
Blue	19	13	18	30	4		84		27		16	19	12		74		18	15	22	19	24		98	256

The most striking feature of the table is the marked predominance of the red over the white. Here the red reaches 73% of the total number of reactions, and inspection shows that this predominance is uniform not only through the groups but even for the individuals. The constancy of this reaction and the fact that it is so much more frequent than the one to the black as compared with the white, would lead one to expect that the red would have the higher percentage in the combination black-red. Such, however, is not found to be the case, although it does happen with one group. If the arrangement of our color-scale in accordance with increasing intensity of stimulus were correct, we should expect a gradually increasing predominance in reactions to colored light over those to white in the first five pairs. Instead of this we find that green and yellow stand nearest to the white, blue and black come next and are almost equal, while red is very much higher than any. In the pairs black-red and black-blue the red holds its predominance over the blue at about the same rate as in the second pair of the direct comparison, red-blue. The wide individual variations, however, in all these reactions to colored light, except perhaps in the case of red-white, indicate that there is nothing very regular, stereotyped, or mechanical about them. The most that can be said is that in a general way the red end of the spectrum furnishes a less intense stimulus to negative reaction than the blue.

A tendency to habit formation was noticed during the course of these experiments, and it is possible that this may have influenced the results somewhat. Many individuals apparently formed a habit of going to a certain corner as soon as they were reset at the centre. The positions in which they were set were varied and they were headed in different directions, but within a minute after they were released in the middle of the box they would be found in their favorite corner. This was especially the case with no. 38 in Table VI, and I think accounts in some measure for the persistent avoidance of the white. In no case did this continue throughout the whole series, but would sometimes be noted for two or three days at a time in the case of an individual. What were the controlling factors in this habit formation, the means by which orientation and recognition were effected, I was unable to determine.