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
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. Gibson and Walk described their visual cliff apparatus in the following way:
"The cliff is a simulated one and hence makes it possible not only to control the optical and other stimuli (auditory and tactual, for instance) but also to protect the experimental subjects. It consists of a board laid across a large sheet of heavy glass which is supported a foot or more above the floor. On one side of the board a sheet of patterned material is placed flush against the undersurface of the glass, giving the glass the appearance as well as the substance of solidity. On the other side a sheet of the same material is laid upon the floor; this side of the board thus becomes the visual cliff."
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.
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 (Berger, 2000).
Later research has demonstrated, however, that children as young as three-months are able to perceive the visual cliff. When placed over the apparent "edge," their heart rate quickens, eyes widen and breathing rate increases. 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 (Campos, et al., 1978).
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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.