Studies of Visual Depth Perception: III. Choice Behavior of Newly Hatched Chicks on a Visual Cliff

Abstract

Gibson and Walk ( 1960) have reported recently their interesting comparative experiments on a new and novel visual depth perception apparatus, the visual cliff. They stated that the age of their chicks was less than 24 hr. when tested on the visual cliff. The writer wished they had been more specific about the age, for if their chicks were as young as 3 hr, old, they would have substantiated an informal observation by Fishman and Tallarico (1960) of the ability of newly hatched chicks to perceive visual depth to at least a distance of 1 ft. Since they did not report the ages as precisely as would have been necessary to compare results of the two studies, the primary purpose of the present experiment was, therefore, to determine the choice behavior of 3-hr.-old chicks on a visual cliff. The secondary purpose was to follow up a direction taken by Gibson and Walk regarding the primacy of visual cues in determining the choice behavior of an S on the centerboard of the visual cliff. Using kids and goats as Ss, Gibson and Walk have stated that With the pattern held immediately beneath the glass, the animal would move about the glass freely. With the optical floor a foot below the glass, the animal would immediately freeze into its defensive posture. Despite experience of the tactual solidity of the glass, the animals neuer learned to function wirhout optical lupport. Their sense of security or danger continued to depend upon the visual cues that give their perception of depth (pp. 64-66, emphasis added). Chicks are like kids and goats and unlike rats and cats with regard to possessing stiff whiskers about their noses. Rats and cats, with their vibrissae to receive tactual cues from the solid surface of the glass over the deep end of the apparatus, behave differently on the visual cliff. The nocturnal rat shows no preference for deep or shallow side; whereas the cat prefers the shallow side. Gibson and Walk did not report whether chicks, when given the opportunity to receive tactual cues through their feet and by pecking at the glass, favored these cues over the visual ones. It would be predicted that chicks after experience of the solidity of the glass would choose the shallow side as do kids, goats, and cats. METHOD Design In attempting to follow the methodology of Gibson and Walk, the writer was faced with the quantification of repeated experience of the tactual solidity of the glass. How much time per trial? How many trials? What interval of time separated the trials? The decision made here was to vary the duration of a single trial. Within one trial, an S may receive experiences. The experimental chicks were given a trial of either