Ainsworth assumed that a child who cried a little as the parent went toward the door, but was easily mollified when she returned, picked the child up, and tried to soothe it, was a securely attached infant, called Type B. About two-thirds of the infants she studied showed this pattern, and most studies conducted since have affirmed this proportion. About 20 percent didn't cry when the mother left, and ignored the mother when she returned. Ainsworth assumed that the lack of interest in the mother's absence and return implied an insecure attachment, called Type A. Finally, about 15 percent of the children cried intensely when the mother left, and were so upset when she returned that they couldn't be soothed. Ainsworth presumed that this pattern, too, implied an insecure attachment, called Type C.
The second important fact was that the observations in the home revealed that the infants called securely attached were the most content, cried the least, and were the easiest to soothe. The students classified the mothers of these infants as extremely sensitive with their children. These data are the bases for Ainsworth's landmark book in 1978, Patterns of Attachment. Neither Ainsworth nor her students considered the possibility, which Ainsworth had noted in Uganda, that the Type B, securely attached infants were temperamentally the easiest babies to care for. That's why they didn't get extremely upset when the mother left them alone in the Strange Situation and were easily soothed when she returned. It's not surprising that the mothers of these infants would appear to the students to be sensitive in the home setting, since it's easy to be a sensitive parent if you have an easy baby.
Moreover, it's worth asking whether a 30-minute observation in an unfamiliar laboratory room could accurately reflect the consequences of many thousands of hours of interaction between the mother and infant in the home during the prior year. This assumption seems to me to be hard to swallow.
It's important to recognize that Bowlby and Ainsworth's work first gained currency at a time when important changes in American society made their ideas particularly attractive. These changes include the public's brooding on the horrors of World War II and the new economic structures that were transforming the traditional family that had dominated Western culture during the prior 200 years. Young mothers were now entering the workforce in unprecedented numbers and needed to find surrogate care for their babies, often in day care centers. This disruption in the time-honored form of infant care by mothers provoked a contagion of worry among professionals and parents. Could infants be cared for adequately if they didn't have the full-time attention of their mothers? This worry had a long tradition in Europe as well as America. In the middle of the 18th century, Jean-Jacques Rousseau wrote that when women are good mothers, their sons will be good husbands and fathers. Sigmund Freud thought that mothers' nursing and toilet-training practices affected adult personality. Siegfried Bernfeld, a leading Austrian-American expert on education and child development, declared in 1929 that the mind of the adult was directly related to the experiences of the opening months of life.
Thus, while Bowlby's ideas weren't novel, his theory supported the many citizens who were bothered by the changes in rearing practices because they believed that only the biological mother could provide the love every infant needed. Mother love—warm, consistent, readily available—was presumed to be the key to mental health. I, too, held that belief in late 1975, when my colleagues and I studied the impact of day care on Boston infants during their first 29 months. But during the succeeding years, my observations and study of the literature on attachment theory have led me to question its basic assumption: namely, that the quality of attachment in infancy has a permanent effect on the child, independent of future experiences or the child's social class and culture.
The evidence indicates clearly that serious neglect or abuse of infants during the first year or two can harm the child's future psychological development. No one quarrels with that statement. But it's less obvious that, for the more than 90 percent of infants who don't suffer serious abuse, the variation in mothers' sensitivity with their infants also constrains future personality, as attachment theory would want us to believe. I want to be clear on this point. There are no studies to date that have investigated the mother-infant interaction in the first year with a large group of infants from all social classes, followed these children to age 20, and demonstrated that insensitive mothers usually produced less happy adults than sensitive mothers, when social class and culture are controlled. Thus, this aspect of attachment theory remains a hunch.