LINKAGES Perception and Human Development

125
Recognizing the Perceptual World
reality is also shaped by experience, including the experience of living in a particular culture (Chua, Boland, & Nisbett, 2005).
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How do infants perceive the
world? (a link to Human
Development)
FIGURE
W
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e have seen that perception is influenced by the knowledge and expePerception and Human
rience we gain over time, but what
perceptual abilities do we start with? To learn
Development
about infants’ perception, psychologists have
studied two inborn patterns called habituation
and dishabituation. Infants stop looking when they repeatedly see stimuli that they perceive to be the same. This is habituation. If they see a stimulus that is perceived to be
new and different, they resume looking. This is dishabituation. Using the habituation/
dishabituation technique, researchers have found that newborns can perceive differences in stimuli showing various amounts of black-and-white contrast but that they
cannot yet distinguish differences between colors (Burr, Morrone, & Fiorentini, 1996).
Other studies using the same methods have shown that newborns can perceive differences in the angles of lines (Slater et al., 1991). Taken together, these studies suggest
that we are born with the basic components of feature detection.
Are we also born with the ability to combine features into perceptions of whole
objects? This is still a matter of debate. We know that at one month of age, infants concentrate their gaze on one part of an object, such as the corner of a triangle (Goldstein, 2002). By two months, though, their eyes systematically scan around the edges of
the object. This change suggests that they are now perceiving the pattern, or shape, of
the object, not just its component features. However, other researchers have found that
newborns show dishabituation (that is, they pay attention) when a familiar set of features are combined in a new way. So even newborns appear to notice and to keep track
of the ways some stimulus features are put together (Slater et al., 1991).
Infants may also be innately tuned to perceive at least one important complex pattern of features: the human face. In one study of newborns, patterns such as those in
Figure 3.29 were moved slowly past the infants’ faces (Johnson et al., 1991). The infants
moved their heads and eyes to follow these patterns. But they tracked the face-like pattern shown on the left side of Figure 3.29 significantly farther than any of the nonfaces. The difference in tracking in this study and others indicates that infants can tell
faces from nonfaces and are more interested in faces, or at least in face-like patterns
(Simion et al., 2003; Valenza et al., 1996). Why should this be? Investigators who take
an evolutionary approach suggest that interest in human faces is adaptive because it
helps newborns focus on their only source of food and care.
Other research on perceptual development suggests that our ability to accurately perceive depth and distance develops more slowly than our ability to recognize shapes (see
Figure 3.30). For example, infants’ ability to use binocular disparity and motion cues
to judge depth appears to develop sometime after about three months of age. They do
not use textural gradients and linear perspective as cues to depth until they are five to
seven months old (Arterberry, Craton, & Yonas, 1993; Bhatt & Bertin, 2001).
3.29
Infants’ Perceptions of
Human Faces
Newborns show significantly greater interest in the face-like pattern at the far left
than in any of the other patterns. Evidently, some aspects of face perception
are innate.
Source: Johnson et al. (1991).