What Is a Visual Cliff?

Baby seeing a visual cliff
Barbara Peacock / The Image Bank / Getty Images

A visual cliff involves an apparent, but not actual drop from one surface to another. This tool was originally developed to determine if infants had developed depth perception. A visual cliff is created by connecting a transparent glass surface to an opaque patterned surface. The floor below has the same pattern as the opaque surface. This apparatus creates the visual illusion of a cliff while protecting the subject from injury.

History of the Visual Cliff

How do infants perceive depth? In order to investigate depth perception, psychologists E.J. Gibson and R.D. Walk developed the visual cliff test to use with human infants and animals. Earlier research had revealed that infants will respond to various depth cues even before they are able to crawl. Depth cues as any type of visual clue that allows people to detect depth in a visual scene. These can include both monocular cues such as relative size and overlap, or binocular cues such as retinal disparity. Gibson and Walk were interested in whether or not an infants ability to perceive depth is a learned behavior or if it was, as they suspected, innate.

Gibson and Walk described their visual cliff apparatus as a large sheet of heavy Plexiglass that is used to create a simulated cliff. The glass is supported a foot or more off the floor.

On one side of the glass, a high contrast patterned fabric is pressed up against the underside to make the glass appear solid and substantial.

At the other side of the glass, the same material is laid on the floor below the glass, creating the visual illusion of a cliff. This allows researchers to test infant perception while still ensuring the safety of their young subjects.

In the test, a child is placed on one end of the platform and the caregivers stands on the other side of the clear surface.

The assumption was that if a child had developed depth perception, he or she would be able to perceive the visual cliff and would be reluctant or refuse to crawl to the caregiver. It was also assumed that infants who still lacked depth perception would crawl happily to their caregivers without even noting the apparent drop.

Gibson and walk concluded that the ability to perceive depth emerges sometime around the age that an infant begins to crawl. The fear of heights, they suggested, is something learned later in infancy as gain experience with bumps, scrapes, and falls.

Understanding the Visual Cliff

Initially, psychologists believed that perception of the visual cliff was a matter of physical and visual maturity. Babies could see the difference by the age of eight-months, while younger infants with less developed depth perception could not see the cliff. Because six-month-old infants could be enticed to wiggle across the visual edge, while ten-month-old babies refused to cross the threshold, it was assumed that the younger children had not yet developed depth perception while the older children had.

Later research, however, has demonstrated that children as young as three-months are able to perceive the visual cliff.

When placed over the apparent "edge," their heart rates quicken, eyes widen, and breathing rates increase. So if these infants can perceive the visual cliff, why would they be willing to crawl off what appears to be a straight drop down? The issue is that children of this age do not yet fully realize that the consequence of going over this visual cliff is potentially falling. This realization only comes later when the child begins to crawl and gains real experience with taking tumbles.

More Psychology Definitions: The Psychology Dictionary


Berger, K. S. (2000). The developing person: Through childhood and adolescence. (5th ed.). New York: Worth Publishers.

Campos, J.J., et al. (1978). The emergence of fear on the visual cliff. In Michael Lewis and Leonard A. Rosenblum (Eds.). The development of affect. New York: Plenum.

Gibson, E.J. & Walk, R.D. (April 1960). The "Visual Cliff". Scientific American.

Continue Reading