Studies on Conditioned Responses in Fishes. Part I.

Abstract

SUMMARY It has been shown by experiments formulated upon the conditioned response principle that the blenny, Blennius gattorugine, is able to perceive and to profit by very small changes in its environment. This fish is able to form conditioned motor responses using food as unconditioned stimulus, towards a momentary increase of 0-4C, or more, in the temperature of the surrounding water. It is also able to form similar conditioned motor responses towards a momentary decrease in the salinity of the surrounding water, of as little as 3 parts per 1000, or towards a change of greater magnitude (up to 37 parts per 1000). Conditioned responses have been established in the wrasses, Crenilabrus inelops and Labrus bergylta, towards visual stimuli of varying kinds. It appears that these fishes can discriminate after differential training between one or two sources of light, and between monochromatic red, green, yellow, or violet light, but not readily between even comparatively large differences in intensity of a luminous source. These results are those obtained upon dark-adapted fishes. More extensive experiments will be necessary before a final statement is made upon their capacity for colour discrimination.