Bowlby interpreted maternal sensitivity as a sign of a mother’s “respect” for her baby. From my perspective, the message sought by an infant born to a species in which maternal commitment is far from guaranteed is more nearly “You will be cared for no matter what.” The attention paid by human infants to the rhythms of turn-taking and the give-and-take in their relationship with their mother is exquisitely nuanced.29 This perpetual testing of maternal responsiveness is different from what goes on in ape babies whose ancestors were never out of tactile contact with their mothers to begin with. Such infants had both less occasion and less need to monitor the whereabouts and intentions of their mothers. Human babies all have “special needs,” and in Chapter 9 I consider some of the long-term implications of that vulnerability.
CONSEQUENCES OF TIME OFF MOTHER
According to a classic Bowlbian scenario, absence makes the infantile heart grow if not fonder at least more apprehensive and clingy. The more inconsistently a mother responds, the more insecurely attached her infant will be, rendering him hypervigilant if not outright anxious. The more that hominin mothers worried about such questions as “Shall I ask my mother to hold the baby while I crack these nuts?” or “Should I carry my baby with me on a long trek to gather food, or leave him with auntie?” or “Should I get rid of this child altogether?” the more ambivalent her responses were going to be, and the more natural selection would have favored youngsters temperamentally inclined to keep a watch on facial expressions or body tones that signal states of mind relevant to maternal commitment, and to respond accordingly.
In Mother Nature: A History of Mothers, Infants and Natural Selection, I reviewed the selective pressures that ambivalent mothers exert on infants, acknowledging the millions of infants through historical and evolutionary times who were abandoned at birth by their mother either because she lacked social support or because (in her eyes) the baby did not pass muster. Space does not permit revisiting such emotionally charged and sensitive topics as why human infants are born so plump (compared with other apes) and so “adorable” or why human newborns are under special selection pressure to prove that they are “worth rearing.”30 Here, I simply take as given that through evolutionary time human newborns confronted a special challenge in eliciting maternal commitment in the postpartum period, and I focus on the much less drastic situation, asking how babies respond to brief and routine separations from an otherwise committed mother.
Psychologists already know that the more direct physical contact there is between a mother and her infant, the less time each party spends looking into the face of the other or seeking what Bowlby, quoting the novelist George Eliot, referred to as “the eyes of love” (“A child forsaken, waking suddenly . . . seeth only that it cannot see the meeting eyes of love”).31 This observation applies to other apes and holds up across human cultures.32 In one of the very few controlled experimental studies of mother-infant eye contact, psychologists Manuela Lavelli and Alan Fogel found that human babies out of physical contact with their mothers seek eye contact more. Observing babies between one and three months of age, Lavelli and Fogel found that being out of direct contact with their mother’s body (being propped up on a couch nearby, for example) stimulated infants to look for their mother more and, having located her, to look into her face significantly longer.33
Among other apes as well, reduction in tactile contact produces a need to reestablish the bond through other means. Recently, Kim Bard and her colleagues found that the more time a mother chimpanzee spent cradling her baby close or grooming him, the less time the two spent looking into each other’s faces. The more they are deprived of touch, the harder little apes strive to reestablish contact through visual means.34
Under natural conditions, nonhuman ape babies are almost never out of touch with their mothers until they are capable of scampering off and returning on their own initiative. By contrast, in contemporary hunter-gatherer societies babies are taken off their mothers by others many months before they can locomote on their own. Babies passed around in this way would need to exercise a different skill set in order to monitor their mothers’ whereabouts. As part of the normal activity of maintaining contact both with their mothers and with sympathetic alloparents, they would find themselves looking for faces, staring at them, and trying to read what they reveal.
Infants separated from their mothers might be comforted, entertained, and provided with edible treats by caregivers, or they might be lugged about nonchalantly and have their treats taken away by envious older sibs. The proximity of adults within earshot would keep a lid on behaviors like teasing but would not put an end to these little threats altogether. Over the first months of life, highly stimulating contacts—emotionally rewarding for the most part, but not always—set the stage for a new kind of ape equipped with differently sensitized neural systems, alert from a very early age to the intentions of others. This novel nervous system would in turn have been exposed to selection pressures that favored the survival of any child born with slightly better aptitudes for enlisting, maintaining, and manipulating alloparental ministrations. In this way, natural selection would lead to the evolution of cognitive tendencies that further encouraged infants to monitor and influence the emotions, mental states, and intentions of others. Traits that helped babies stay connected even when out of physical contact helped these vulnerable infants survive.
STAYING IN TOUCH WITHOUT TOUCH
Primatewide, two conditions cause babies to vocalize more: when they are separated from their mothers and when they are in tactile contact with her but interacting with someone else.35 During the first three months of life, infant chimpanzees are just as reactive toward alloparents who approach as their human counterparts are. Human and nonhuman ape babies alike respond to stimulation from others with long looks and vocalizations. We can see this in the case of human-reared chimpanzees. For example, one 19-week-old chimpanzee infant was more likely to respond to a strange human than to either its own mother or a familiar human caretaker.36 However, under natural circumstances a chimpanzee that age would not have opportunities to interact with alloparents, and even if it did, the encounter was unlikely to enhance survival.
All ape babies complain loudly and pitifully in emergency situations that separate them from their mother. But human infants, frequently out of direct contact with their mother’s body, required a more nuanced coping repertoire. They needed to find a way to vocalize in nonemergency situations—some new means of maintaining contact and engaging others through sound. The repetitive, rhythmical vocalizations known as babbling provided a particularly elaborate way to accomplish this.
Human babies begin to babble at about seven months.37 Typically, they pass through this stage as the “milk teeth” first peek through, beginning with two tiny incisors on the bottom gums, then four more on top, eventually twenty in all—sharp little teeth that help babies chew their first other-than-milk foods, whether soft fruit or tubers and meat premasticated by someone else. So far the only other primates observed to pass through a babbling phase (if by babbling we mean repetitive strings of adultlike vocalizations uttered without obvious vocal referents) all belong to the family Callitrichidae. Along with humans, these marmosets and tamarins are among the very few primates who qualify as full-fledged cooperative breeders, with both shared care and provisioning.
Nonhuman primate babbling has been particularly well studied by Chuck Snowdon and Margaret Elowson among tiny, Ewok-like pygmy marmosets from Brazil. Shortly after birth, these Cebuella pygmaea babies begin to utter complex streams of vocalizations, stringing together sounds common to the adult repertoire. It is significant that babbling emerges in this species right about the time that caregivers other than the mother take over, because both in captivity and in the wild these distinctive vocalizations serve to attract alloparental attention. Thus Snowdon and Elowson hypothesized that attracting caretakers is actually the function of marmoset babbling.38 In some callitrichids, such vocalizations actually eli
cit food, leading marmosetologists to label them “chuck” calls in honor of one of their first describers, Chuck Snowdon.39
Fed or not, babies keep on babbling even after they make contact with a caretaker, suggesting that babbling plays a role in maintaining as well as establishing relationships with parents and alloparents.40 If Snowdon and Elowson are correct, it is scarcely surprising that babbling has not been heard among continuous-care-and-contact species like chimpanzees, who indeed may not even possess the physiological apparatus for babbling.41 Chimpanzee infants simply don’t need it. Among humans, however, with their very different caretaking history, babbling is universal.
Recently, the anthropologist Dean Falk sought to explain babbling—as well as motherese—with a somewhat different scenario of Pleistocene caretaking. In Falk’s view, these two ways of communicating evolved in the human lineage so that bipedal, newly hairless mothers could reassure infants no longer able to cling to them.42 In what she called her “putting-the-baby-down hypothesis,” Falk proposed that protohuman mothers would need to set their babies on the ground in order to have their own hands free to work. She wrote, “I have a difficult time imagining early hominin mothers not setting their babies down frequently in order to free their hands for noncarrying tasks prior to the invention of baby slings.”43 However, apart from prosimians and muriquis, it is very rare for wild primates or people in foraging societies to park babies.44 Falk was starting from the assumption that our protohuman ancestors resembled naked versions of chimpanzees, lacking hair for babies to cling to but no more likely to take advantage of alloparents’ assistance than other apes are.
I agree with Falk that motherese, like infant babbling, is composed of contact-promoting as well as reassuring vocalization. However, in the human case, I suspect the function was different than say the clucking sounds a mother muriqui makes after parking an older infant in the canopy of some tree while she forages nearby unencumbered.45 Rather, in the hominin case, I suspect that both babbling and motherese evolved in response to the need for babies and mothers to maintain contact while infants were being held by others. Motherese reassured babies of their mothers’ whereabouts and intentions, while babbling attracted the attention of mothers and allomothers alike.
Falk is probably right that once language evolved (or coevolved with other human attributes) a baby’s imitation of adult sounds provided useful practice for language acquisition.46 But in my view, the recursive and syntactical elaborations of human language arose long after cooperative breeding evolved, and with it the need for infants to attract attention and maintain relationships with others. The power of babble, I suspect, preceded the gift of gab by more than a million years.47
THE CAST WIDENS, THE PLOT THICKENS
Most primates and all apes are born with the same basic need to feel securely attached, but humans need more reassurance still. Why should this be so? Throughout the 1950s and 1960s Bowlby and his followers took continuous-care-and-contact mothering as a given for all primates and paid little attention to emerging information on shared care.48 When data from the first detailed observations of hunter-gatherer childrearing among the !Kung started to come in, these findings were interpreted through a Bowlbian lens. In time, however, critics of this dominant view began to refer to mother-only caretaking models as “monotropic.”49
In fairness to Bowlby, he did not remain as dogmatically mother-focused as some critics imply. Prodded by Ainsworth (who was heavily influenced by her field experience in Uganda), he began to mention how much help mothers needed and to acknowledge assistance from various sources. At the opening of a lecture he delivered in 1980, Bowlby noted that “very often it is the other parent [who provides this help]; in many societies, including more often than is realized our own, it comes from a grandmother. Others to be drawn into help are adolescent girls and young women. In most societies throughout the world these facts have been, and still are, taken for granted and the society organized accordingly. Paradoxically it has taken the world’s richest societies to ignore these basic facts.”50
Yet scratch him hard and Bowlby’s view of infant development was profoundly mother-centered. Through attachment theory’s first half century, research focused on the infant’s relationship with this one other person. From an evolutionary perspective, however, mothers were far from the whole story. Even as attachments to individuals other than the mother were gradually taken into account, it usually came about in the context of highly charged and polarized late-twentieth-century debates over daycare.
Studies were specifically designed to compare developmental outcomes between children cared for at home by their mother and children cared for outside the home by unrelated childcare providers in daycare centers of variable quality. The questions asked were how “secure” or “insecure” an infant’s attachment to his mother would be; how well-adjusted, compliant, or aggressive an infant would become in early childhood; and so forth. Such studies provided little information about the developmental effects of multiple caretakers per se simply because the studies had been designed to learn whether or not there were any harmful effects from daycare.51 Hence, results from the first large-scale empirical study of the effects of daycare came as a real surprise to hardline Bowlby disciples who were convinced that babies develop best with full-time care from mothers.
By the end of the twentieth century, officials at the National Institute of Child Health and Human Development (NICHD) were growing increasingly concerned as some 62 percent of U.S. mothers with children under age six worked outside the home, and the majority of these women were going back to work within three or four months of giving birth. Yet in spite of heated debates over daycare, and with some 13 million preschoolers in some form of care by persons other than their mothers, there had never been a large-scale, carefully controlled study of daycare’s effects. Beginning in 1991, the NICHD funded a consortium of top psychologists to follow 1,364 children whose families came from ten different locales in the United States and spanned diverse ethnic and economic backgrounds, all using different childcare arrangements.52
As the data poured in, it became clear that many factors influenced developmental outcomes for children in daycare. These included the quality of the infant’s relationship with the mother at home, how many hours away from home the child spent, child-to-caretaker ratios, and staff turnover at the daycare center. But the key finding was that maternal and alloparental sensitivity and responsiveness to infants’ needs were better predictors of developmental outcomes like self-control, respect for others, and social compliance than (within limits) actual time spent away from the mother was. In the case of inattentive or neglectful mothers, children were actually better off in daycare, where their needs were often more routinely or predictably met.
The massive NICHD study was informative on many fronts. But the main message was that it was not the presence of the mother per se that mattered most (though quality of the child’s attachment to the mother was invariably important) but how secure infants felt when cared for by familiar and responsive people. Given that mothers are not likely to quit working outside the home, practically speaking the news that rampant daycare was not crippling the nation’s children was welcome indeed. However, the results were also discouraging because good, or even adequate, daycare is so rarely available, and it tends to be expensive. Even in the best-equipped daycare centers with trained staff, turnover among caregivers is a persistent problem. It is difficult to find a substitute for familiarity and the sense of trust a child develops in kin or as-if kin with long experience responding to his particular temperament and needs.53
The findings about daycare also raised questions about evolutionary models for child development. If Bowlby and the early attachment theorists were right that infants in humankind’s “environment of evolutionary adaptedness” were almost entirely cared for by their mothers, why were infants managing to adapt as well as they did to multiple-caretaker contexts? And why were outcomes for children in high-quality
daycare centers generally pretty good?
EXPANDING ATTACHMENT THEORY
Prior to the big NICHD study, there had been relatively little systematic research on the effects of multiple caretakers per se, much less studies of multiple attachments. Nevertheless, from the 1970s onward, a handful of psychologists began to ask about the role of infant attachments to individuals other than the mother—and in particular, attachments to fathers. Michael Lamb was among these pioneers. A psychologist, Lamb subscribed to the main outlines of attachment theory, never doubting that a distressed baby would preferentially seek his mother. But Lamb found the mother-centered assumptions implicit in classical attachment theory overly narrow.
Initially, he simply wanted to see more attention paid to involved fathers like himself. Analyzing data from one of the first studies of attachment between infants and “others,” Lamb found (as he expected) that babies were attracted by their mother’s sensitive and predictable care, her high-pitched motherese, and the satisfying breast she offered, and they became attached to her. But babies in his study also became emotionally attached to their father after comparatively brief periods of exposure. When both mother and father were involved in childcare, babies became attached to both, although they interacted differently with each.54 With fathers, babies tended to interact in short and intense bouts of vigorous (and exciting) play. (The descriptions reminded me of watching my own husband throw our toddlers up above his head and then catch them in midair—never missing, but all the same definitely exciting and memorable.) Infants became attached to their fathers even though the typical father in the United States was in direct contact with his baby just under an hour a day, substantially less than the amount of face-time fathers spend with babies in most hunter-gatherer societies.55
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