The Domesticated Brain (12 page)

The day the world stood still

I can still vividly recall it as if it were yesterday. Those of a certain age will remember exactly where they were on that fateful day in 2001. It was a September afternoon in the UK but a bright, sunny morning in New York with crisp blue skies. Colleagues knew that I had a television in my office and had come in to watch the terrifying news unfolding. Two planes had been flown into the World Trade Center and now there was dense smoke billowing out of both. People were jumping to their deaths. If you saw the footage, then you, like me, will probably still have those events emblazoned on your memory as the world changed for ever.

For some, these recollections have become
flashbulb memories
, as if the scene were lit up in harsh lighting to capture everything – even trivial details of little relevance. Our memories can be supercharged with detail when we experience something terrifying. This is because we become more alert and attentive, on the lookout for danger as our hippocampus, the seahorse-shaped repository for long-term memories in each of the temporal lobes, receives input from the
amygdala – a structure the size of an almond, also in each temporal lobe, that is active when you laugh, cry and scream in terror.
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They also don’t let you forget.

Experiences that eventually become memories start out as patterns of neural firing or traces that come flooding into the brain. Raw sensory input is interpreted into representations and given meaning. This in turn updates and changes the knowledge we have about the world by forming memories. Whether details become consolidated into the memory stores of the hippocampus depends on filtering mechanisms that are regulated by the action of neurotransmitters released by the amygdala during surprising, arousing or rewarding events. The neurotransmitters are the molecules that trigger activity in the connecting gaps between neurons. Flashbulb memories stimulate the amygdala to invigorate the activity of the hippocampus, thereby enhancing the memory trace for those events that move us the most.
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As the world watched in helpless shock, a generation would never forget what they saw. But even some from the next generation of unborn babies were left with the legacy of that terrible day.

Post-traumatic stress disorder (PTSD) is an anxiety condition that appears weeks after traumatic events such as rape, battle and other acts of violence. It is characterized by recurrent dreams, flashbacks and flashbulb memories, as if the victim is haunted by the past. After witnessing 9/11, one in five New York residents who lived closest to the World Trade Center suffered from PTSD. Rachel Yehuda, a New York psychiatrist, followed up a sample of pregnant women from this group. She found that these women had abnormal
levels of cortisol in their saliva – a hormone that is released as a natural response to stress but depleted in individuals with PTSD.
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Different hormones and neurotransmitters form part of an elaborate signalling system that the brain uses to activate different functions. Some have general effects whereas others seem to be more specific in the roles they play.

The depleted levels of cortisol in the chronically stressed mothers were to be expected. But what was unexpected was the plight of their unborn children. One year after the attack, infants born to the mothers who had developed PTSD also had abnormal levels of cortisol compared to babies of other mothers who did not develop the disorder after witnessing 9/11. Vulnerable mothers had passed something on to their children. As Yehuda put it, children of PTSD victims bore ‘the scar without the wound’.
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It is well known from various disease models that events early in development can have consequences later in life. There is a whole category of substances known as
teratogens
(literally, ‘monster makers’) that, if the pregnant mother is exposed to them, can result in birth defects. Various drugs, both legal and illegal, as well as environmental toxins such as radiation or mercury can damage the unborn child. However, some diseases resulting from harmful substances take decades to manifest. My own father-in-law died from mesothelioma, a rare form of lung cancer that was probably caused by exposure to asbestos when he was growing up as a child in South Africa. Toxins that enter our bodies can alter the functions of our cells but lie dormant for years. Over a lifespan we may replenish our cells many times, but each reproduction
of the cells can carry genetic time bombs that lie in wait for the right circumstances to kill us. Physical substances like asbestos from the environment are obvious candidates as being poisonous to our systems, but what about exposure to psychological toxins? How can our mind’s reaction to non-physical events, such as watching something horrific, produce long-term consequences? How could a mother’s stress in response to 9/11 cross over to the next generation? What could she possibly pass on to her unborn child?

Jerry Kagan, a Harvard developmental psychologist, reckons that around one in eight babies are born with temperaments that make them highly irritable, which is due to their overreactive limbic systems. They startle easily and respond excessively to sudden noises.
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The limbic system mobilizes the body for action and its circuitry includes the amygdala. It triggers a cascade of hormones and neurotransmitters that prepare the body to respond to threat. Reactivity of the limbic system is a heritable trait meaning that it can be passed on to the child in the genes they inherit.
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These are the highly-strung children who find uncertainty and strange situations upsetting. Depending on how they react to sudden sounds as a four-month-old baby, you can even predict personality many years later.
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Reactivity is like a disposition, which makes some of us twitchy, but others are born more laid-back and chilled. Maybe mothers who developed PTSD after 9/11 gave birth to babies with a nervous nature because of their genes.

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
.
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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.
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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.
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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.
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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.
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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.
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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.
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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.