The visual cliff is a laboratory apparatus designed to test depth perception in infants and young animals. It consists of a glass-covered surface with a shallow side and an apparently deep side.

Eleanor Gibson and Richard Walk introduced the device in the 1960s. Infants old enough to crawl are placed on the center board and encouraged by a caregiver to cross either the shallow or the deep side. Most infants refuse to crawl onto the deep side, indicating that they perceive the drop-off. Younger infants who cannot yet crawl may still show physiological signs of awareness of the depth. Similar results have been obtained with chicks, lambs, and other species that must navigate early in life.

The visual cliff demonstrated that depth perception is present at least by the age of crawling and does not require extensive experience of falling. It remains a classic illustration of the early emergence of a fundamental perceptual ability.

A baby’s hesitation at the edge of the apparent drop reveals that the cliff is seen as real.