11.2 How Infants Learn About the Environment

When an infant emerges from the womb, he or she is confronted by a world of sights, sounds, and other sensations that William James (1890/1950) termed “one great blooming, buzzing confusion” (p. 488). How do infants learn about the environment that surrounds them? What do they know, early on, about that world?

The Infant as Explorer

Infants’ sensory systems all function at birth (although one sense, vision, is still quite immature). On the day they are born, infants will turn toward sounds, turn toward anything that touches their faces, turn away from unpleasant odors, suck a nipple more readily for a sweet liquid than for a sour one, and orient their eyes toward high-contrast or moving visual stimuli (Maurer & Maurer, 1988). Within a short time after birth, they not only respond to stimuli but do so selectively, in ways that seem well designed for learning.

Infants Look Selectively at Novel Objects

Hundreds of experiments have shown that babies gaze longer at new stimuli than at familiar ones. When shown a pattern, they look at it intently at first and then, over the course of minutes, look at it less and less—a phenomenon referred to as habituation. This decline in attention does not stem from general fatigue; if a new pattern is substituted for the old one, infants immediately increase their looking time—a phenomenon called dishabituation. Similarly, if shown the new and old patterns at the same time, they look more at the new one than the old one. This preference for novelty makes sense if we assume that infants are actively trying to learn about their world. They look at new stimuli because they have more to learn from them than from old stimuli, which they have already explored.

Infants’ bias for looking at novel stimuli is so reliable that developmental psychologists use it to assess infants’ abilities to perceive and remember. Babies who look significantly longer at a new stimulus than at one they have already seen must perceive the difference between the two and must, at some level, remember having seen the old one before. In one such experiment, infants as young as 1 day old perceived the difference between two checkerboards with different-sized squares and remembered that difference over the seconds that separated one trial from the next (Friedman, 1972). This was shown by the fact that they looked longer at the checkerboard that they had not seen before when they were given a choice. Later, you will read about research in which infants’ selective looking is used to assess their knowledge and expectations about the physical world.

Infants Seek to Control Their Environments

Within a few weeks after birth, infants begin to show a special interest in aspects of the environment that they can control. In one experiment, 2-month-olds smiled and attended much more to a mobile that moved in response to their own bodily movement than to a motor-driven mobile that they could not control (Watson, 1972). In another experiment, 4-month-olds learned quickly to make a particular movement to turn on a small array of lights, but lost interest and responded only occasionally after they became good at this task. When the conditions were changed so that a different movement was needed to turn on the lights, the infants regained interest and made another burst of responses (Papousek, 1969). Their renewed interest must have been generated by the new relationship between a response and the lights because the lights themselves were unchanged. Apparently, the babies were interested not so much in the lights per se as in their ability to control them.

In still another experiment, infants as young as 2 months old, who had learned to turn on a video and sound recording of the Sesame Street theme song by pulling strings tied to their wrists, showed facial expressions of anger when the device was disconnected so that they could no longer control it (Lewis et al., 1990). In subsequent, similar experiments, 4- and 5-month-old babies showed facial expressions of both anger and sadness at losing control of their ability to turn on the recording, even when the recording still came on as often as before but under the control of the experimenter rather than themselves (Sullivan & Lewis, 2003). Apparently, it was the loss of control, not the loss of opportunities to see and hear the recording, that upset them. The desire to control our environment seems to be a facet of human nature that exists in every phase of development, and its function seems obvious: We, more than any other species, survive by controlling our environment.

Infants Explore Increasingly with Hands and Eyes Together

During their first 3 or 4 months of life, babies, like puppies and other young mammals, put practically anything that they can reach into their mouths. They mouth objects in ways that seem designed to test the objects’ properties. With time, however, they gradually give up their puppy ways and explore increasingly in the more uniquely human way, with hands and eyes together, rather than with mouths (Rochat, 1989).

By 5 or 6 months, babies regularly manipulate and explore objects in the sophisticated manner that researchers label examining (Ruff, 1986). They hold an object in front of their eyes, turn it from side to side, pass it from one hand to the other, rub it, squeeze it, and in various other ways act as if they are deliberately testing its properties. Such actions decline dramatically as the infant becomes familiar with a given object but return in full force when a new object, differing in shape or texture, is substituted for the old one (Ruff, 1986, 1989). As evidence that examining involves focused mental activity, researchers have found that babies are more difficult to distract, with bright visual stimuli, when they are examining an object than at other times (Oakes & Tellinghuisen, 1994).

Infants vary their examining in ways consistent with an object’s properties. They preferentially look at colorfully patterned objects, feel objects that have varied textures, shake objects that make a sound when shaken, squeeze objects that are pliable, and pound with objects that are hard (Bourgeois et al., 2005; Lockman & McHale, 1989). Other experiments have shown that infants do, indeed, learn about objects’ properties through such examination. In one experiment, 9-month-olds explored toys that produced interesting nonobvious effects when manipulated in certain ways, including a can that wailed when tilted and a doll that separated into two parts when pulled. The infants soon learned to produce each toy’s unique effect, and when given a new toy that was similar (but not identical) to the one they had just explored, they immediately tried to produce the previously experienced effect. If the new toy differed in its basic structure from the original one, they did not try to produce the effect but explored the toy afresh, as if intent on discovering its unique properties (Baldwin et al., 1993).

A small scientist By 5 to 6 months of age, infants learn about the properties of objects by manipulating them with their hands while watching intently to observe the effects.

Geri Engberg/The Image Works

Infants do not have to be taught to examine objects. They do it in every culture, whenever objects are in their reach, whether or not such behavior is encouraged. Roger Bakeman and his colleagues (1990) studied the exploratory behavior of infants among the !Kung San, a hunting-and-gathering group of people in Botswana, Africa, who have been relatively uninfluenced by industrialized cultures. (The !K in !Kung stands for a click-like sound that is different from the pronunciation of “K” in the Roman alphabet.) !Kung adults do not make toys for infants or deliberately provide them with objects for play. Yet !Kung babies examine objects that happen to be within their reach—stones, twigs, food items, cooking utensils—in the same manner as do babies in industrialized cultures; and, as in industrialized cultures, their examining increases markedly in frequency and intensity between about 4 and 6 months of age. !Kung adults do not encourage such behavior because they see no reason to, yet they recognize its value and do not discourage it. Their view of child development seems to be well summarized by one of their folk expressions, which can be translated roughly as “Children teach themselves” (Bakeman et al., 1990).

Infants Use Social Cues to Guide Their Exploration

Although babies act upon and explore their environments independently of adult encouragement, they often use cues from adults to guide such actions. Beginning in the latter half of their first year of life, babies regularly exhibit gaze following (introduced in Chapter 4)—that is, they watch the eyes of a nearby person and move their own eyes to look at what that person is looking at (Woodward, 2003). Such behavior really does depend on attention to the eyes; if the adult’s eyes are closed or covered, the baby does not look preferentially in the direction the adult is facing (Brooks & Meltzoff, 2002). Gaze following ensures that infants will attend to those objects and events that are of greatest interest to their elders, which may be the most important things to attend to and learn about for survival within their culture. It also helps to promote language development. If the adult is naming an object, it is useful to the child to know what object the adult is looking at and naming. Researchers have found that babies who show the most reliable gaze following learn language faster than those who exhibit less gaze following (Brooks & Meltzoff, 2008).

Another achievement during the latter part of the first year is infants’ ability to view other people as intentional agents—individuals who cause things to happen and whose behavior is designed to achieve some goal (Bandura, 2006). This is first clearly seen around 9 months of age when infants engage in shared attention (sometimes called joint attention) with another person (Tomasello, 2009; Tomasello & Carpenter, 2007). This involves a three-way interaction between the infant, another person, and an object. It usually begins with the adult pointing out objects that both the infant and adult can see. By 12 months of age, infants will point to alert others to objects they are not attending to (Liszkowski et al., 2007), and between 12 and 18 months of age they will point to direct an adult’s attention to an object the adult is searching for (Liszkowski et al., 2006).

On the surface, being able to share a perceptual experience may not seem like a very noteworthy cognitive milestone, but humans may be the only species to do this. For example, although chimpanzees and some monkeys will follow another’s gaze in some situations (Bräuer et al., 2005) and point out things to others (Leavens et al., 2005), there is little evidence that they engage in shared attention (Herrmann et al., 2007; Tomasello & Carpenter, 2005).

By the time they can crawl or walk freely on their own (toward the end of their first year), infants engage in what is called social referencing—they look at their caregivers’ emotional expressions for clues about the possible danger of their own actions (Walden, 1991). In an experiment with 12-month-olds, not one crawled over a slight visual cliff (an apparent 30-centimeter drop-off under a solid glass surface; see Figure 11.4) if the mother showed a facial expression of fear, but most crawled over it if her expression was one of joy or interest (Sorce et al., 1985). In another experiment, 12-month-olds avoided a new toy if the mother showed a facial expression of disgust toward it, but they played readily with it otherwise (Hornik et al., 1987).

Figure 11.4: Is it safe? Babies refused to crawl over the “visual cliff” if they saw an expression of fear on their mother’s face, but most crawled over it if her expression showed joy or interest.

©Mark Richards/PhotoEdit–All rights reserved.

Infants’ Knowledge of Core Physical Principles

Peek-a-boo The results of selective-looking experiments suggest that babies even much younger than this one know that objects continue to exist when out of view. Nevertheless, they take delight in having that understanding confirmed, especially when the object is a familiar, friendly person.

Brand X Pictures/Thinkstock

We all share certain assumptions about the nature of physical reality. We assume, for example, that objects continue to exist even when they disappear from view; that two solid objects cannot occupy the same space at the same time; and that if an object moves from one place to another, it must do so along a continuous path. We expect these principles always to be true, and when they seem to be violated, we usually assume that our senses have been somehow deceived, not that the principles have been overturned.

At what age do people begin to make these core assumptions about physical reality? Some theorists, such as Elizabeth Spelke and her colleagues (Spelke, 2000; Spelke & Kinzler, 2007) propose that infants possess core knowledge about the physical world, needing relatively little experience with their physical environment to arrive at these insights. Similarly, David Geary (2005a) proposed that infants are born with a small set of skeletal competencies specialized to make sense of the physical world. Stated another way, this position argues that infants are not born as blank slates, as the seventeenthcentury philosopher John Locke argued, but are prepared by evolution to make sense of their physical world so that some things are more easily learned than others.

Infants Reveal Core Knowledge in Selective-Looking Experiments

Just as babies look longer at novel objects than at familiar ones, they also look longer at unexpected events than at expected ones. Researchers have capitalized on this with many experiments that have used selective looking to assess what infants expect to happen in specific conditions (Baillargeon, 2004, 2008).

A classic example of such a violation-of-expectation experiment is illustrated in Figure 11.5. First, in the habituation phase, the baby is repeatedly shown a physical event until he or she is bored with it, as indexed by reduced time spent looking at it. In the example shown in the figure, that event is the back-and-forth movement of a hinged screen over a 180-degree arc. Then, in the test phase, the infant is shown one of two variations of the original event. One variation, the impossible event, is an illusion, arranged with mirrors or other trickery, that appears to violate one or more core physical principles. In the example, this event is one in which an object placed behind the rotating screen fails to prevent the screen from rotating all the way back. It is as if the object magically disappears each time the screen rotates back and then magically reappears each time the screen rotates forward. The other event, the possible event, does not violate any physical principle. In the example, this event is one in which the rotating screen stops in each rotation at the place where it would bump into the object behind it.

Figure 11.5: Evidence for understanding of object permanence in very young infants After being habituated to the back-and-forth movement of the screen, infants as young as 3.5 months looked longer at the impossible event, in which the screen seemed to go through and obliterate a solid object, than they did at the possible event.

(Adapted from Baillargeon, 1987.)

Notice that the two test events are designed so that, on purely sensory grounds, the possible event differs more from the original habituation event than does the impossible one. Thus, if infants respond simply on the basis of sensory novelty, they should look longest at the possible event. But if they respond from knowledge of physical principles, they should look longest at the impossible event because that differs most from what they would expect to happen. In fact, using the setup shown in Figure 11.5, Renée Baillargeon (1987) found that infants as young as 3.5 months old looked longer at the impossible event than at the possible event. This result is strong evidence that even such young infants understand, in some way, that solid objects do not normally pass through and temporarily obliterate other solid objects.

Similar experiments have demonstrated infants’ knowledge of other core principles. For instance, babies as young as 2.5 to 3 months expect an object to appear behind the screen where it was originally placed, not behind a different screen (Baillargeon, 2004); expect a rolling ball to stop at a solid barrier rather than pass through it (Spelke et al., 1992); and expect a stationary ball to remain stationary unless pushed by another object (Spelke et al., 1994). Of course, young infants do not manifest entirely the same expectations about the physical world that adults, or even 2-year-olds, do. Core principles may be present early on, but nuances related to them are acquired with age and experience (Baillargeon, 2008). For example, Baillargeon (1994, 1998) found that 4-month-olds expected a box to fall to the ground when it was released in midair, but did not expect it to fall when it was set on the edge of a shelf with most of its weight hanging off the shelf. Only by 6 to 7 months did babies show evidence that they expected the unbalanced box to fall.

Infants Reveal Less Knowledge in Search Tasks Than in Selective-Looking Tasks

The findings supporting infants’ early knowledge of core principles surprised many developmental psychologists. Previous research, using a different procedure, had suggested that infants under about 5 months of age lack even the most basic understanding of object permanence, the principle that objects continue to exist when out of view. The pioneer of that research was the famous Swiss developmental psychologist Jean Piaget (1936/1963), who tested infants’ understanding by having them search for hidden objects. In the simplest of his tests, the simple hiding problem, an attractive toy is shown to a baby and then is placed under a napkin as the baby watches. Babies younger than about 5 months typically follow the toy with their eyes as it disappears under the napkin, but do not reach for it once it is there; they almost immediately seem to lose interest in it. Piaget and his successors interpreted this result as evidence that babies this age completely lack the concept of object permanence.

Self-produced locomotion promotes cognitive development When babies are able to move around on their own, they gain new perspectives on their world and make rapid gains in their ability to solve Piagetian search problems.

Marc Romanelli/BlueMoon Stockagefotostock

Between about 6 and 9 months of age, most infants solve the simple hiding problem but fail the changed-hiding-place problem, also developed by Piaget (Wishart & Bower, 1984). In the first phase of this test, the toy is hidden under one napkin for a series of trials, and the baby retrieves it each time. Then, in the crucial phase, the toy is hidden under another napkin, right next to the first, as the baby watches. Despite having watched the object disappear under the new napkin, the baby reaches toward the original napkin. Piaget concluded that at this age the emerging understanding of object permanence is still very fragile; when pitted against a learned motor habit (reaching toward the original hiding place), the habit wins out. Only by about 10 to 12 months do most infants solve this problem.

Let us provide a real-life example of a changed-hiding-place problem:

Why do infants younger than 5 months, who appear to understand object permanence in selective-looking experiments, fail even the simplest of Piaget’s tests of object permanence? Nobody knows for sure, but a number of researchers have suggested that the difficulty in Piaget’s tests has to do with the ability to plan the correct arm and hand movement to obtain the hidden object (Baillargeon, 1998; Keen, 2003). In order to retrieve a hidden object, the baby not only must know where the object is, but also must be able to use that knowledge to guide his or her reaching movement. Babies under 5 months of age have no difficulty reaching for objects that are in full view, but may be unable to use mental images of hidden objects to guide their reaching. Consistent with this interpretation, researchers have found that infants as young as 3 to 4 months old who fail to reach for a hidden object nevertheless look at the location where the object was hidden, even after a moment’s distraction (Ruffman et al., 2005).

Dramatic improvement in infants’ search abilities occurs shortly after they learn to crawl or in other ways move about on their own (Campos et al., 2000). In one experiment, 8-month-olds were tested in a series of search tasks, including a version of Piaget’s classic changed-hiding-place problem (Kermoian & Campos, 1988). One group had learned to crawl at least 9 weeks before the tests; a second group had not learned to crawl but had at least 9 weeks of experience moving around in walkers at home; and a third group had neither learned to crawl nor been provided with walkers. Approximately 75 percent of the babies in the first two groups succeeded on the changed-hiding-place problem, compared with only 13 percent of those in the third group. For infants to move about on their own, they need to coordinate their vision with their muscular movements in new ways to avoid bumping into objects; as they move, they also see objects from new and varied perspectives. Such experiences may well help them learn to plan all sorts of effective movements, including those involved in retrieving hidden objects.