What experimental apparatus has been used to study depth perception in infants?

The answer is visual cliff. This apparatus was shaped by psychologists Eleanor J. Gibson and Richard D. Walk at Cornell University to examine depth perception in human and animal species. This apparatus permitted 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 glass with a patterned cloth under it to simulate the appearance of a cliff.