During Mao Zedong's reign from 1950s to mid-1970s, millions of Chinese infants lived in austere residential day care centers and saw their mothers on an irregular schedule. I saw some of these infants in 1973, when I visited the country. Yet there's no evidence to indicate that this practice created a large number of adults with a mental illness. Mothers from northern Germany believe infants have to learn to regulate their distress, and therefore they don't go to them every time they cry—which strikes American observers as insensitive. These infants learn to control their emotions when frustrated, and, not surprisingly, they're less likely to cry when the mothers leave them in the Strange Situation, and are classified as Type A, insecurely attached. But, as with the Chinese, there's no evidence suggesting that northern German adults are especially vulnerable to psychological problems. Toward the end of World War II, Anna Freud and her colleagues studied a small group of children who'd been imprisoned in a Nazi concentration camp since their birth. Most of these children had never had a stable relation with a mother. The psychologist Sarah Moskovitz found these adults, who were scattered around the world, with the help of Anna Freud's secretary. In 1982, she published Love Despite Hate, which summarized her interviews with them. She noted their affirmation of life. There were no suicides, and only one person had been arrested for a crime. These data are inconsistent with attachment theory. I could cite many more studies leading to the same conclusion: neither behaviors in the Strange Situation nor the parent's behaviors in the first year are powerful predictors of adult personality or mental illness among children from the same social class and ethnic group. Bowlby's ideas remain a hypothesis, not a proven fact. If they're true, we'll have to wait for new investigations to demonstrate their validity.
While we await more evidence of the validity of attachment theory, it may help to consider the role of infant temperaments. I've spent the past 35 years researching the impact of two specific temperaments on development, and it'll come as no surprise that I claim their relevance here. Temperament refers to an inborn predisposition to experience certain feelings and display particular behaviors during the early years. My colleagues and I have found that the temperamental biases of infants are the first conditions contributing to later variation in mood and behavior. They don't determine a particular personality, but they do limit the traits that a person can acquire. The evidence suggests that a person's observable behaviors as seen by others—what Carl Jung called their "persona"—change over time. However, their private feeling tone, colored by their temperament, seems to be preserved for a longer period.
Although we're still at an early stage of identifying the potentially large number of temperamental biases, research has established that a vulnerability to distress and vigilance to unfamiliar or unexpected events, as opposed to minimal vulnerability to distress, represent two important temperaments. My colleagues and I have followed several hundred middle-class, Caucasian children from their initial assessment at 16 weeks to their 18th birthday. At 4 months, the babies were exposed to a series of harmless and unfamiliar sights, sounds, and smells. About 20 percent of the infants arched their backs, flailed their limbs, and cried in response to these unexpected events. We called these infants "high-reactive." By contrast, in response to the same stimuli, 40 percent of the infants remained relatively unruffled. We called those infants "low-reactive." I believe that these low reactives would become Ainsworth's Type B infants.
We observed these children at ages 1, 2, 4, 7, 11, 15, and 18, and found that the infants' tendency either to become easily distressed or to remain placid in the face of unexpected change endured for many, but not all, children. As teens, more high-reactive children reported a number of unrealistic anxieties over confronting crowds, strangers, unfamiliar cities, riding a subway, and the future. The low-reactive children had few such worries, and were likely to approach new situations and people with gusto. Relatively speaking, life was easier for them.
Readers might argue that these distinctive personality profiles resulted from differences in the infants' attachment to their parents. However, that's unlikely, because Doreen Arcus, a professor at the University of Massachusetts, visited the homes of high- and low-reactive infants several times in their first year, and didn't notice important differences in the mothers' sensitivity or the infants' emotional bond to the mother. In addition, we gathered physiological measures suggesting that the high-reactive children were born with a neurobiology that rendered their amygdalae more excitable than the amygdalae of the low-reactive children. Apparently, the two temperamental groups inherited different neurobiological profiles.