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Perceiving Depth
Depth perception is the ability to perceive three-dimensional space and to accurately judge
distance. Without depth perception, we would be unable to drive a car, thread a needle, or simply
navigate our way around the supermarket (Howard & Rogers, 2001). [8] Research has found that
depth perception is in part based on innate capacities and in part learned through experience
(Witherington, 2005). [9]
Psychologists Eleanor Gibson and Richard Walk (1960) [10] tested the ability to perceive depth in
6- to 14-month-old infants by placing them on a visual cliff,a mechanism that gives the
perception of a dangerous drop-off, in which infants can be safely tested for their perception of
depth (Figure 4.22 "Visual Cliff"). The infants were placed on one side of the “cliff,” while their
mothers called to them from the other side. Gibson and Walk found that most infants either
crawled away from the cliff or remained on the board and cried because they wanted to go to
their mothers, but the infants perceived a chasm that they instinctively could not cross. Further
research has found that even very young children who cannot yet crawl are fearful of heights
(Campos, Langer, & Krowitz, 1970). [11] On the other hand, studies have also found that infants
improve their hand-eye coordination as they learn to better grasp objects and as they gain more
experience in crawling, indicating that depth perception is also learned (Adolph, 2000). [12]
Depth perception is the result of our use of depth cues, messages from our bodies and the
external environment that supply us with information about space and distance.
Binocular depth cues are depth cues that are created by retinal image disparity—that is, the
space between our eyes, and thus which require the coordination of both eyes. One outcome of
retinal disparity is that the images projected on each eye are slightly different from each other.
The visual cortex automatically merges the two images into one, enabling us to perceive depth.
Three-dimensional movies make use of retinal disparity by using 3-D glasses that the viewer
wears to create a different image on each eye. The perceptual system quickly, easily, and
unconsciously turns the disparity into 3-D.
An important binocular depth cue is convergence, the inward turning of our eyes that is required
to focus on objects that are less than about 50 feet away from us. The visual cortex uses the size