Describe the Findings and Conclusions of Gibson and Walks Visual Cliff

Gibson and Walk used 36 participants all between the ages of 6 and 14 months, all of whom were able to crawl. The infants were placed, one at a time, in the centre of the glass on a board. Their mothers stood at one side of the platform, and attempted to coax the child towards them. If the child  moved off the centre of the platform onto the “deep” side, this would suggest that the infant had no depth perception and if they appeared to prefer the “shallow side”, refusing to cross onto the “deep” side, this would suggest that the infant had developed depth perception.

Gibson and walk used several controls in order to eliminate any confounding variables or bias. In order to stop any reflections from the surface of the glass, the platform was lit from beneath. To ensure that the patterned fabric effectively created the illusion of depth, the cloth was replaced with a homogenous and Gibson and Walk found that, following this adaption, rats were unable to distinguish between the deep and shallow sides. To verify the experiment further, Gibson and Walk placed the fabric on both sides flush with the bottom of the glass and found that the rats moved indiscriminately between both sides. When one both sides were lowered, the rats refused to move off the centre board.

However, human infants cannot be tested on the Visual Cliff until at least 6 months (when most babies acquire mobility) and it is argued that in this time the infants have a chance to develop depth perception. Gibson and Walk found a way to overcome this problem however; they tested on a range of animals, some of which were mobile within 24 hours of birth. They also tested the animals by placing them on the “deep” side of the platform, and observing their reaction. This allowed Gibson and Walk to investigate whether any of the animals would be calm, and be able to move on the deep side if they realised it was safe.

The use of animals gave insight into perception further as they were able to compare the reactions of animals that are more visual (such as cats, which rely on vision greatly to hunt) and animals that rely more on other senses (such as rats, which are mainly nocturnal and rely more on tactical cues from their vibrissae. It also allowed them to investigate with dark-reared animals, to explore which cues they learn to respond to first. It was also possible to manipulate the spacing and sizes of the check pattern, to see how this could affect depth perception and the different cues such as motion parallax and the distance of the pattern, which decreases and increases the size and spacing of the pattern elements projected on the retina.