Yehuda thinks not. She found that the lowered cortisol effect was only present for those mothers who were in the third trimester of their pregnancy, so it could not just be the genes working alone. There seems to be a critical period when exposure to stress alters the child’s development. To begin to understand how such a maternal impression restricted to a window of vulnerability could possibly happen, we need to look at the history of difficult childhoods and the way that they affect how we respond to stress as adults.
War child
World War II disrupted normal life for thousands of families. In Europe, many children were separated from parents by the turmoil and ended up in institutions. Even though they were generally cared for, many of them grew up into socially impaired and delinquent teenagers. To explain this, John Bowlby, a British psychiatrist, proposed that these children had missed out on a critical phase in development that he called attachment.12 Bowlby believed that attachment was an evolutionary adaptive strategy to form a secure, nurturing bond between the mother and her infant. This early experience not only protects the vulnerable child, but also provides the necessary foundation for coping mechanisms to deal with problems later in life. Without this early secure attachment, the child would grow up psychologically impaired.
Bowlby was inspired by the ornithological work of Konrad Lorenz, who had shown that many bird species form a close-knit bond between mother and chicks.13 This attachment begins with imprinting, where the young chicks will pay special attention to and follow the first moving thing they see. Famously, Lorenz demonstrated that he could make baby goslings imprint on him by incubating the eggs and hand-rearing the chicks when they hatched. In the wild, imprinting was critical for survival by maintaining the proximity of the chicks to the hen, which is why the chicks would imprint to the first moving thing, usually the mother. Investigation of the chick brain revealed that it is innately wired to follow some shapes more than others and that chicks quickly learn the distinct features of their own mother, to tell her apart from others.
Human infants also pay special attention to face patterns at birth and very quickly learn their mother’s face.14 However, primate, and in particular human, early social attachment is unlikely to be as rigid as bird imprinting. Whereas the need to imprint in birds has to be satisfied fairly quickly, primates can take a bit longer to learn to know each other. Another important difference between birds and babies is that humans are not up and running about for at least a year. Whenever the human infant needs their mother, they simply have to cry, which will soon send most mothers scurrying to their infant’s side. A distressed infant’s cry is one of the most painful things to hear (which explains why crying babies on aeroplanes can be so upsetting for everyone around them). This ‘biological siren’ ensures that babies and mothers are never that far apart.15 Infants from around six months of age show separation anxiety when physically separated from their mother, a state characterized by tears and stress as signalled by the rise in cortisol levels in both the infant and mother. These levels eventually return to normal when baby and mother are reunited.16
With time, both mother and baby learn to tolerate further episodes of separation, but the mother remains a secure base from which the toddler can explore their surroundings safely. Imagine Bowlby’s securely attached toddlers as baseball or cricket players: they feel secure when they are touching the bases or while behind their creases, but become increasingly anxious and insecure as they step farther and farther away from them. Without secure early attachment, Bowlby argued that children would never learn to explore novel situations and develop appropriate coping strategies. They would also fail to become properly domesticated, which was why he believed that children separated from their nurturing parents during the war grew up to become delinquent teenagers.
The lost children
Inspired by Bowlby’s work on social attachment and later psychological abnormality, Harry Harlow in the US set out to test an alternative explanation for the long-term effects of deprived childhoods.17 Maybe children were simply not looked after or given adequate nutrition if they were raised in institutions. If you gave them food and warmth, they should be fine. To test this, he conducted an infamous series of studies where he raised baby rhesus monkeys in isolation for differing amounts of time. Although these infant monkeys were well fed and kept in warm, safe environments, they were left alone. This social isolation had profound effects on their development. Monkeys with no social contact as infants developed a variety of abnormal behaviours as adults. They compulsively rocked back and forth while biting themselves, and when they were finally introduced to other monkeys, they avoided them entirely. When the females from this group reached maturity, they were artificially inseminated to become mothers, but they ignored, rejected and sometimes even killed their own offspring.
Harlow discovered that it was not just the amount of time that animals spent in isolation that was critical, but also when they were separated. Those born into isolation were at risk if they spent longer than the first six months without the company of their mother. In comparison, monkeys who were isolated only after the first six months of normal maternal rearing did not develop abnormal behaviour, indicating that the first six months was a particularly sensitive period. Bowlby had originally thought that the primary reason for attachment was to ensure that biological needs for food, safety and warmth were satisfied, but Harlow proved that he was only partly correct – monkeys also needed social interaction from the very beginning.
It turns out that human social development, like that of the monkey, is also shaped by a similar sensitive period of socialization. Back in 1990, following the collapse of Nicolae Ceauşescu’s dictatorship, the world discovered thousands of Romanian children abandoned in orphanages. Ceauşescu had outlawed family planning in an attempt to force women to have more children to increase Romania’s dwindling population. The trouble was that families were unable to support these children and so they were abandoned in the orphanages.
On average, there was only one caregiver for every thirty babies, so there was little social interaction and none of the cuddling or intimacy that you would find in a normal, caring environment. The babies were left to lie in their own faeces, fed from bottles strapped to their cots and hosed down with cold water when the smell became unbearable. When these children were rescued, many of them were fostered out to good homes in the West. Sir Michael Rutter, a British psychiatrist, studied just over one hundred of these orphans who were less than two years of age to see how their early experiences would shape their development.18
On arrival, the orphans were all malnourished and scored low on psychological tests of mental well-being and social interaction. That was to be expected. As time passed, they recovered much of this lost ground in comparison to other adopted children of the same age who had not been raised in the Romanian orphanages. By four years of age, most of this impairment had gone. Their IQs were still below average in comparison to other four-year-olds, but within the normal range that could be expected. However, it soon became apparent that not all was back on track.
Children who had spent longer than six months in the orphanages were failing to catch up with their matched group. Only the children who were rescued before they were six months old went on to a full recovery. The children were followed up again at six, eleven and fifteen years of age. Again as a group they fared much better than expected, given such a horrific start in life, but problems started to appear. Those who had spent the longest time in the orphanage were beginning to show disturbed hyperactive behaviour and difficulties in forming relationships. Just like Harlow’s monkeys, social interaction during that first year was crucial for normal development. To understand what is so important about having someone around to look after you and not just to give you food and warmth, we have to consider what upsets babies.