<P> The visual cliff apparatus was created by psychologists Eleanor J. Gibson and Richard D. Walk at Cornell University to investigate depth perception in human and animal species . This apparatus allowed them to experimentally adjust the optical and tactical stimuli associated with a simulated cliff while protecting the subjects from injury . The visual cliff consists of a sheet of Plexiglas that covers a cloth with a high - contrast checkerboard pattern . On one side the cloth is placed immediately beneath the Plexiglas, and on the other, it is dropped about 4 feet below . Since the Plexiglas supports the weight of the infant this is a visual cliff rather than a drop off . 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 . </P> <P> Gibson and Walk (1960) hypothesized that depth perception is inherent as opposed to a learned process . To test this, they placed 36 infants, 6 to 14 months of age, on the shallow side of the visual cliff apparatus . Once the infant was placed on the opaque end of the platform, the caregivers (typically a parent) stood on the other side of the transparent plexiglas, calling out for them to come or holding some sort of enticing stimulus such as a toy so that the infant would be motivated to crawl across towards them . It was assumed if the child was reluctant to crawl to their caregiver, he or she was able to perceive depth, believing that the transparent space was an actual cliff . The researchers found that 27 of the infants crawled over to their mother on the "deep" side without any problems . A few of the infants crawled but were extremely hesitant . Some infants refused to crawl because they were confused about the perceived drop between them and their mothers . The infants knew the glass was solid by patting it, but still did not cross . In this experiment, all of the babies relied on their vision in order to navigate across the apparatus . This shows that when healthy infants are able to crawl, they can perceive depth . However, results do not indicate that avoidance of cliffs and fear of heights is innate . </P>

What do psychologists investigate with a visual cliff