The visual cliff is an apparatus created by psychologists Eleanor J. Gibson and Richard D. Walk at Cornell University to investigate depth perception in human and other animal species. It consists of a sturdy surface that is flat but has the appearance of a several-foot drop part-way across. The visual cliff apparatus allowed them to conduct an experiment in which the optical and tactile stimuli associated with a simulated cliff were adjusted while protecting the subjects from injury.[1]
Using a visual cliff apparatus, Gibson and Walk examined possible perceptual differences at crawling age between human infants born preterm and human infants born at term without documented visual or motor impairments.[2]