The Story of Psychology (73 page)

By the time a human is twelve, the brain has an estimated 164 trillion synapses.
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Those connections are the wiring plan that establishes the brain’s capabilities. Some of the synaptic connections are made automatically by chemical guidance, but others are made by the stimulus of experience during the period of rapid dendrite growth. Lacking such stimulus, the dendrites wither away without forming the needed synapses. Mice reared in the dark develop fewer dendritic spines and synaptic connections in the visual cortex than mice reared in the light, and even when exposed to light never attain normal vision. Kittens reared in a stroboscopic environment, where they see only during flashes of light, fail to develop cortical cells sensitive to movement; when they are grown cats, they see the world as a series of stills. If one eye of a young monkey is kept shut during the critical period, the neurons of that eye never catch up to those of the other eye. Thus, maturation provides—for a limited time—a multitude of potential nerve pathways among which experience makes the choice, “hard-wiring” those circuits needed for perception.
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FIGURE 19
Brain Development: These drawings of neurons in the visual cortex show the flourishing and development of the human brain in the first half-year of life.

Why should nature have done that? Since we can learn all through life—and all learning, at any age, involves the creation of new synaptic connections—why should perceptual development be possible only at a critical period and not later? Apparently, the developing brain’s “use it or lose it” policy is efficient and economical of resources; the growing neurons are preserved by myelinization (which wraps them in a fatty protective sheath), and those sensory connections that are used are further myelinized to make them more permanent. Since the essential experiences are almost always available for carrying out this process at the right time in brain development, the pruning of unused connections fine-tunes the brain structure and provides far more specific perceptual powers than would result from genetic control alone of synapse formation.
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Here again we see the vague old terms “nature” and “nurture” taking on more precise meaning; we see mind being constructed not by the addition of nurture to nature but by the interaction between them, each
affecting and being affected by the other. Mysteries begin to fade away; wonders take their place.

Unlike personality researchers, whose primary interest is measurement, developmentalists are concerned with natural history. They watch personality grow from birth on, and seek to identify the forces that shape it. And in contrast to psychoanalysts, who base their theories of personality development chiefly on what they hear from adult patients, develop-mentalists base theirs on firsthand evidence.

Part of that evidence adds much detail and meaning to psychoanalytic ideas about mother-infant attachment. This has been a leading topic of developmental research ever since 1952, when the World Health Organization published
Maternal Care and Mental Health
by the English psychoanalyst John Bowlby, who studied children raised in institutions, found them deficient in emotional and personality development, and attributed that to their lack of maternal attachment.

Bowlby theorized that the infant is genetically programmed to behave in certain ways (crying, smiling, making sounds, cooing) that evoke care and hence survival, and that the mother’s nurturance engenders attachment in the infant at a “sensitive period” of his or her development. This powerful special bond, which gives the infant a sense of security, is crucial to normal personality development; without it, said Bowlby, the child is likely to develop “an affectionless character” and to be permanently vulnerable to psychopathology.
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Bowlby’s views aroused great interest—and discomfort—in America, where the rising divorce rate and, a little later, the women’s movement caused a growing number of mothers to work, leaving their children with caretakers. Many child psychologists and developmentalists doubted that the sensitive period is as specific and crucial, or the mother as all-important and irreplaceable, as Bowlby said. But most of them agreed that, under normal circumstances, attachment to the mother (or mother substitute) does occur and is a major force in personality development.

Intriguing evidence of the harm done by the lack of attachment was shown in a 1965 study of infant smiling conducted in Israel. It compared babies raised under three conditions: in their own families, in
kibbutzim
(collective settlements) where they are reared in large houses by
professional caretakers but often fed by their mothers for the first year, and in institutions. It is rare for one-month-old infants to smile at a strange human face, but with each passing week they do so more and more often, the behavior reaching a peak at about four months and then declining slowly. In the study, all three groups smiled often at strange female faces by the fourth month, but at eighteen months while the family-reared infants were only slightly less responsive than at four months, the kibbutz-reared infants were only about half as much so, and the institution-reared infants less likely to smile than they had been at one month.
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But smiling is a byproduct of attachment, not a measure of it. Researchers needed such a measure, and in the late 1960s Mary Ainsworth, a former colleague of Bowlby’s who had come to America, devised a relatively easy one. Known as “the Strange Situation,” it has been the mainstay of attachment research ever since. In the Strange Situation, the infant and mother are put in an unfamiliar playroom while the researcher watches them through a one-way mirror. Eight different scripts are followed, one at each visit. In one, the mother leaves the room briefly; in another, a stranger comes in while she is there; in a third, when she is not; and so on.

From about eight months to two years, the infant typically cries when the mother leaves the room (“separation anxiety”), and when she returns goes to her and clings to her. (There are, of course, temperamental differences that make one infant more anxious than another; the findings of the Strange Situation are generalizations.) If a stranger enters and does not smile or talk, an infant of seven or eight months will look at the mother and in a little while start to cry (“stranger anxiety”), although at three or four months the same infant probably would have smiled. Stranger anxiety dissipates within a few months, but separation anxiety continues to rise until early in the second year, then declines gradually throughout the year.
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There are several explanations for the appearance and disappearance of the two reactions, but the most widely held is that with growing mental capacity, the infant is better able to evaluate the situation. Stranger anxiety wanes as the infant gains the ability to recall pleasant experiences with other strangers, separation anxiety as the infant becomes capable of understanding that the mother will return.
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Ainsworth’s original aim was to see how infants react when their mothers are absent, but she unexpectedly found that how they react when the mother comes back was even more interesting. Some are glad
to see her and go to her to cling or be held; others ignore or avoid her; and still others squirm, hit, or kick her if she tries to hug them. Ainsworth called the first reaction (shown by about 70 percent of one-year-olds) “secure attachment,” the second kind (20 percent) “anxious-avoidant attachment,” and the third kind (10 percent) “anxious-resistant attachment.”

After studying all three kinds in greater depth, Ainsworth and other researchers concluded that avoidant attachment occurs when the mother is emotionally inexpressive, resistant attachment when the mother has been inconsistent in responding to the infant’s needs. Still other researchers have ascribed avoidant and resistant attachment to such factors as the mother’s personality traits, lack of expressiveness, negative feelings about motherhood, rejection of the infant, and harsh responses to the infant’s crying or demands.

Some psychologists later identified variants of Ainsworth’s three attachment styles, finding her explanations too pat. Jerome Kagan is one.

In a study of his own, Kagan found that mothers of the ostensibly less securely attached babies had careers outside the home and, while psychologists might regard them as less nurturing, may have tried to make their infants self-reliant and able to cope with separation. The mothers of the more securely attached infants may have been overprotective and prevented them from developing such inner security.
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A valuable study conducted in the 1980s used the Strange Situation to measure the attachment of 113 one-year-olds to their mothers and five years later evaluated their behavior and mental health by means of a questionnaire given their mothers and another given their teachers. Of the boys who had been securely attached at one year of age, only 6 percent showed signs of psychopathology; of those who had been insecurely attached, 40 percent did. (Girls, for unknown reasons, showed no
such connection between the quality of early attachment and later psychopathology.) The research team cautiously concluded that the results “lend partial support to the hypothesis that the quality of the early mother-infant attachment relationship predicts later social-emotional functioning.”
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Most research on the development of the emotions has been focused on the first two years of life, and for good reason. According to Michael Lewis and his colleagues at the Institute for the Study of Child Development, University of Medicine and Dentistry of New Jersey, the primary emotions (joy, fear, anger, sadness, disgust, and surprise) appear during the first half year, the secondary or “derived” emotions (embarrassment, empathy, and perhaps envy) in the second half of the second year, and other secondary emotions (pride, shame, and guilt) soon after. Studies of infants’ videotaped facial expressions by Carroll Izard and his colleagues and students at the University of Delaware have yielded related findings.
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Until a generation ago, developmentalists had no theory of the development of emotions; now they have several. These differ on various issues, the most important being whether the development of the emotions is due chiefly to the maturation of specific neural circuits or to social learning of emotional behaviors and their displays. In both views the emotions are said to assume specific form through learning, but one holds that the major determinant is maturation, and the other, cognitive capacity and training. Consider a piece of the evidence for each side:

First, the maturational view:

A team of researchers at the National Institute of Mental Health set out to pinpoint the earliest appearance of altruism or care giving in children by observing children in play groups and at home. Altruism is a form of behavior based on the emotion of empathy; the team expected to see the first signs of empathy at about age six, as predicted by psychoanalytic theory, but they could see that younger children—as young as three—seemed distressed when another child was in pain or unhappy. Going back still farther, they looked for empathy in toddlers by having mothers simulate pain or a choking cough at home in the presence of their child. Some years ago, Dr. Carolyn Zahn-Waxler, a member of the team, told the author of this book what the team, to its own surprise, found: “Even a one-year-old might look distressed when his mother cried, and in children only a few months older, we’d see unmistakable expressions of concern for the other person.” These reactions are almost universal and show up in predictable forms at relatively predictable
stages and ages. “That suggests to me,” she concluded, “that whatever part experience plays, the organism is hard-wired with a tendency to respond empathetically.”
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In very recent years she has been proven quite right: Brain scans—a subject we’ll come to later—provide abundant evidence that particular brain circuits respond in similar ways to the circuits of others in emotional states, and that this empathy-generating neural architecture develops very early in the infant brain and hence is very likely hard-wired.

Second, the cognitive-developmental view:

A curious bit of methodology, first used with children several decades ago, consists of unobtrusively dabbing rouge on a child’s nose and then putting him or her in front of a mirror. Until they are about twenty months old, most children either do nothing or try to touch the rouge spot in the mirror; at twenty months and older, most of them touch the spot of rouge on their noses. This is taken as evidence of the emergence of a sense of self; children realize that the image in the mirror is of them.
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Michael Lewis and a group of colleagues used the mirror-rouge technique to find out when and why the emotion of embarrassment first appears. Most children who touch the rouged spot, they reported, also looked embarrassed (the criteria: an embarrassed smile, a turning away of the head, and a nervous touching of the body), but most non-touchers did not. The team’s conclusion: