Test Subjects in Diapers [Preview]

When do babies recognize the intentions of others--and become capable of deliberate actions themselves?

Toby lies in his crib watching his mother, Claudia, as she does housework. He babbles happily and kicks his legs with delight as one piece of clothing after another disappears into the washing machine. "I wonder if he realizes that I am intentionally picking up this T-shirt to put it into the machine?" Claudia asks. "And does he consciously control his movements?"

Parents aren't the only ones who wonder. Researchers have been asking similar questions in studies during the past two decades. In recent years, they have gained some surprising insights into the cognitive development of infants. As it turns out, even the smallest babies know far more than we have traditionally given them credit for.

For centuries, infants were viewed as virtually passive beings who absorbed little information from their environment and whose movements were almost exclusively reflexive. The situation is very different today: scientists know that a human being learns at an astonishing rate during the first few months after birth, perhaps faster than at any other time in his or her life. Babies explore the world with all senses, and their brains process an abundance of experiences and stimuli. Psychologists are probing exactly when the seeds of reasoning begin to sprout.

Little Test Subjects
How does one study the capabilities of children who cannot yet talk? Psychologists turn to an array of testing techniques based on the systematic observation of baby behavior. First, the procedures take advantage of an infant's natural attentiveness to new objects or situations. The more surprising the situation, the longer the infant focuses. Babies also find dolls, plush animals, unusual sounds and light effects appealing. Second, infants are very imitative, providing another way to delve into their development. Tests do, nonetheless, have to take a youngster's physical progress into account. For instance, tasks that involve grasping and shaking an object are not suitable for a child younger than about six months.

One of the major questions about babies' capabilities that researchers have explored is, Do babies learn from watching the actions of others? For example, suppose a child watches an adult manipulating a puppet that is wearing a glove. The adult removes the puppet's glove and shakes it three times, causing a bell to ring, and then puts the glove back on. After demonstrating this sequence several times, the adult gives the puppet to the baby. While the baby plays with the puppet, researchers analyze their little subject. Surprisingly, children as young as six months make use of their previous observation. They repeat the first step of the action sequence they have observed--taking off the glove--far more often than do members of a control group, who did not see the sequence. Over a 24-hour period, they continue to remember the action, as long as the opportunity to play with the puppet is repeated often enough. Children are not able to master all three steps, however, until they are about 15 to 18 months old.

Another research question is, Do infants merely copy the movements of others, or can they imagine an effect that they then set out to produce? "Conditioning" experiments, popular in the 1960s, established that even newborns can learn to elicit pleasurable effects by making particular movements--that is to say, they can be conditioned at a very early age. They move about and take in and process interesting phenomena in their surroundings almost as soon as they are born. From their experiences they then discover contingency, the relation between their own movements and events that occur in the environment around them. In experiments with nursing newborns, they can learn to suckle at a certain frequency to elicit through a headset the soothing voice of their own mother but not that of another woman. Another way we have studied infants' familiarity with contingency in the lab is with mobiles. The baby lies in a crib, with a string fastened to her ankle and to a mobile. Whenever she kicks, she sees the mobile move. Within a few minutes she discovers this contingency, and she kicks more frequently.

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