Visual Perception: Seeing the World

  1. LO9What visual perception skills do infants have?

From the time of Lee Eng’s birth, everyone who met him felt that he gazed at them intently. His eyes seemed to meet those of visitors. They appeared to bore deeply and knowingly into the faces of people who looked at him.

How good in fact was Lee’s vision, and what, precisely, could he make out of his environment? Quite a bit, at least up close. According to some estimates, a newborn’s distance vision ranges from 20/200 to 20/600, which means that an infant can only see with accuracy visual material up to 20 feet that an adult with normal vision is able to see with similar accuracy from a distance of between 200 and 600 feet (Haigth, 1991).

These figures indicate that infants’ distance vision is one tenth to one third that of the average adult’s. This isn’t so bad, actually: the vision of newborns provides the same degree of distance acuity as the uncorrected vision of many adults who wear eyeglasses or contact lenses. (If you wear glasses or contact lenses, remove them to get a sense of what an infant can see of the world; see the accompanying set of photos.) Furthermore, infants’ distance vision grows increasingly acute. By 6 months of age, the average infant’s vision is already 20/20—in other words, identical to that of adults (Cavallini et al., 2002; Corrow et al., 2012).

Other visual abilities grow rapidly. For instance, binocular vision, the ability to combine the images coming to each eye to see depth and motion, is achieved at around 14 weeks. Before then, infants do not integrate the information from each eye.

Depth perception is a particularly useful ability, helping babies acknowledge heights and avoid falls. In a classic study by developmental psychologists Eleanor Gibson and Richard Walk Richard Walk (1960), infants were placed on a sheet of heavy glass. A checkered pattern appeared under one-half of the glass sheet, making it seem that the infant was on a stable floor. However, in the middle of the glass sheet, the pattern dropped down several feet, forming an apparent “visual cliff.” The question Gibson and Walk asked was whether infants would willingly crawl across the cliff when called by their mothers (see Figure 5-11).

Figure 5-11

Visual Cliff

The “visual cliff” experiment examines the depth perception of infants. Most infants in the age range of 6 to 14 months cannot be coaxed to cross the cliff, apparently responding to the fact that the patterned area drops several feet.

The results were unambiguous. Most of the infants in the study, who ranged in age from 6 to 14 months, could not be coaxed over the apparent cliff. Clearly the ability to perceive depth had already developed in most of them by that age. On the other hand, the experiment did not pinpoint when depth perception emerged, because only infants who had already learned to crawl could be tested. But other experiments, in which infants of 2 and 3 months were placed on their stomachs above the apparent floor and above the visual cliff, revealed differences in heart rate between the two positions (Campos, Langer, & Krowitz, 1970; Kretch & Adolph, 2013).

Still, it is important to keep in mind that such findings do not permit us to know whether infants are responding to depth itself or merely to the changein visual stimuli that occurs when they are moved from a lack of depth to depth.

Infants also show clear visual preferences, starting at the time of birth. Given a choice, infants reliably prefer to look at stimuli that include patterns than to look at simpler stimuli (see Figure 5-12 ). How do we know? Developmental psychologist Robert Fantz (1963) created a classic test. He built a chamber in which babies could lie on their backs and see pairs of visual stimuli above them. Fantz could determine which of the stimuli the infants were looking at by observing the reflections of the stimuli in their eyes.

Figure 5-12

Preferring Complexity

In a classic experiment, researcher Robert Fantz found that 2- and 3-month-old infants preferred to look at more complex stimuli than simple ones. (Based on Fantz, 1961.)

Fantz’s work was the impetus for a great deal of research on the preferences of infants, most of which points to a critical conclusion: infants are genetically preprogrammed to prefer particular kinds of stimuli. For instance, just minutes after birth they show preferences for certain colors, shapes, and configurations of various stimuli. They prefer curved over straight lines, three-dimensional figures to two-dimensional ones, and human faces to nonhuman faces. Such capabilities may be a reflection of the existence of highly specialized cells in the brain that react to stimuli of a particular pattern, orientation, shape, and direction of movement (Hubel & Wiesel, 1979, 2004; Kellman & Arterberry, 2006; Gliga et al., 2009).

Genetics is not the sole determinant of infant visual preferences. Just a few hours after birth, infants have already learned to prefer their own mother’s face to other faces. Similarly, between the ages of 6 and 9 months, infants become more adept at distinguishing among the faces of humans, whereas they become less able to distinguish faces of members of other species (see Figure 5-13). They also distinguish between male and female faces. Such findings provide another clear piece of evidence of how heredity and environmental experiences are woven together to determine an infant’s capabilities (Ramsey-Rennels & Langlois, 2006; Valenti, 2006; Quinn et al., 2008; Otsuka et al., 2012). (See also the From Research to Practice box.)

Figure 5-13

Distinguishing Faces

Examples of faces used in a study that found that 6-month-old infants distinguished human or monkey faces equally well, whereas 9-month-olds were less adept at distinguishing monkey faces than human faces.