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The Eyes of a Child

In the wake of the Second World War, thousands upon thousands of children were left without parents. Six years of warfare on an unprecedented scale had caused a dramatic influx of orphans. Most were homeless, friendless, and hopelessly alone, their entire families slaughtered and their villages bombed to rubble. Their shell-shocked faces neatly encapsulated the horrors that had plagued Europe for over half a decade, and the World Health Organization (WHO) was desperate to help them in any way it could. But building and staffing orphanages wasn’t enough. The WHO strove to correct not just the physical and financial hardships faced by orphans, but the psychological ones as well. They wanted to understand the effects of such profound loss on the human mind in order to better help those who suffered through it. For this they turned to the renowned psychiatrist John Bowlby.

Bowlby was the perfect candidate. An award-winning and well-educated scholar, he had experience working with maladapted and delinquent children and an avowed passion for helping disadvantaged young people. The WHO asked him to write a pamphlet on the psychology of orphans, how the loss of both parents affects children’s mental and emotional development. Bowlby accepted, and the task so captivated him that he made studying children the basis of the rest of career. Attachment theory was an extension of his original work, drawing inspiration from psychology, biology, and ethology in an attempt to explain how and why children bond with their early caregivers. Though received with some reluctance by the academic community of the day, attachment theory ultimately became the go-to model for exploring early child development.

Dr. Mary Ainsworth, Bowlby’s star pupil, reinforced his theory, amending to it various tools and strategies designed to measure and categorize the children it sought to study. Ainsworth’s research begat two intelligent and ambitious disciples: Patricia Crittenden and Mary Main. Crittenden and Main both believed strongly in the basic tenets of attachment theory, and both used the new science as a diving bell with which they plumbed the murky and shifting depths of infant psychology. It is what they found down there — or rather, how they chose to interpret it — that caused a rift to form between them.

Severed Bonds

Do you remember Sophie from the beginning of this book? She wasn’t an only child. She had a sister named Sandra and a brother named Darren, both younger than her. Though their traumatic upbringing forged a certain bond between them, the three siblings were never close. They got along fairly well, all things considered, but were all very different people.

For one thing, Sophie and Sandra reacted very differently to their parents’ fighting. Sophie, we know, cowered in her room, drowning out the noise as best she could and doing everything in her power to avoid the situation. Sandra took the opposite approach. She was a heavier sleeper than Sophie, but on nights where the fighting got heated enough to wake her she would scream and cry and beat her fists against the headboard until her parents came running, drawing their attention to her and away from each other. When things calmed down she seemed more or less content, oblivious to the subtler domestic tensions that buzzed discordantly in Sophie’s ears more or less constantly.

Sophie made self-sufficiency and people-pleasing her mantra. Sandra, on the other hand, relied on her parents for everything. She constantly mooched money, demanded attention, and whined whenever she didn’t get her way. Though she demanded constant affection, she herself was not particularly affectionate, treating her parents with a confused jumble of sycophancy, indifference, and disdain.

Unlike Sophie, Sandra didn’t take well to school. She struggled to pay attention in class and spent most of her time daydreaming and doodling. Though not one to act out, Sandra scarcely made an effort and squeaked by with poor grades. By the time she finished high school she was already married to a man four years older than her, and the only job she could find was at Burger King.

Now an adult, Sandra has three children and barely enough money to feed and clothe them. Her husband works at a warehouse loading boxes of frozen food onto trucks. He spends most of his time playing video games, ignoring Sandra pretty much completely. Sandra takes her aggression out on the children. She constantly calls on Sophie for help, but Sophie has her own problems and there’s only so much she can do.

As for Darren, he was still in the womb when Sophie and Sandra’s home life started to crumble. His mother took care of him as best she could, but some days the weight of her life grew much too heavy and she stayed in bed, ignoring his cries and flicking through channels on a small, grainy television. His father convinced himself that Darren wasn’t really his child and he offered the boy nothing but insults and barbed criticism.

At school, Darren was habitually sent to the principal’s office. He picked fights, talked back to teachers, and disrupted classes. Not a month went by where he didn’t face suspension. Twice he was held back a year for failure to complete any of the course material. In seventh grade, he was expelled for stabbing a classmate in the arm with a compass and had to enroll in another school across town. By grade 10 he was expelled again, this time for selling pot. When he was 18, he was squatting in a friend’s downtown apartment.

Darren worked briefly as a stock boy at a grocery store, but mostly he sells drugs — soft stuff like pot and pills. He doesn’t have the connections or the muscle necessary to move crack or heroin, but he doesn’t really mind. That stuff is far more dangerous to work with, and he doesn’t need to earn that much. He crashes on couches, eats fast food, and spends the rest of his cash on booze and cigarettes. He has a child he never sees with a woman who nearly had him arrested for domestic abuse.

A Tale of Two Theories

Attachment theory, as defined by Dr. Mary Ainsworth, divides 12- to 24-month-old babies into three groups based on how they act in relation to their parents — when and how they seek comfort, the affection (or lack thereof) they display when their parents hold or play with them, and the degree to which they are comfortable exploring their environment. To distinguish between groups, Ainsworth represented each one by a letter, giving us attachment types A, B, and C. Each group of babies has developed a different and distinctly recognizable strategy to ensure that their attachment figure (parent) provides them with protection, comfort, and the necessities of life. Without a successful strategy for attachment to a caregiver, babies would be hopelessly alone and vulnerable to all manner of threats — disease, starvation, predators, and exposure to the elements. Attachment is therefore an evolutionary adaptation to ensure survival.

Groups A, B, and C represent three distinct attachment strategies, each comprised of specific behaviours that children adopt in order to cope with and function in the world around them. The strategies derive from infancy but persist over the lifespan and affect behaviour and mental health into adulthood.

Type B children are securely attached. They are comfortable being left alone for short periods but happy to see their parents return. Type A children, called “avoidant,” tend to avoid contact with caregivers. They have come to expect neglect or disinterest on the part of their guardians, often because their early cries for attention have gone unheeded. As a result, they aren’t bothered by spending short periods of time on their own, nor do they seem at all excited to see their parents when they return. This is in direct contrast to Type C or “reactive/ambivalent” children, who fuss and cry upon being left alone for even a moment, but are not consoled by, and often show resentment toward, their parents’ presence. Type C behaviour is often a response to inconsistent or partial neglect — when a parent comes running at the first sound of their child in one instance, but leaves them unattended for hours in another. Type A behaviours, on the other hand, come from consistent neglect. Children whose parents never answer their cries or react indifferently to their presence learn to seek comfort from themselves, developing a fierce inward yearning for self-reliance and emotional numbness to outside caregivers. There is, we believe, another cause of Type A attachment: “Tiger” parenting. The Tiger Mother, a term popularized by Amy Chua’s 2011 book Battle Hymn of the Tiger Mother, emphasizes control, harsh discipline, and a relentless drive for scholastic pursuits in child-rearing. Proponents of Tiger Mothering argue that children lack the capacity for self-motivation needed to achieve their best, and a firm, strict, and unwavering pressure, applied by the parent, is necessary to make children reach their full potential. The parent becomes a kind of crucible, facilitating the high temperatures necessary to smelt a child’s raw components into a strong, successful adult. However, predicating affection purely on scholastic or musical success can create in a child an overwhelming need to please others. Using affection as a reward for good behaviour is essentially a sort of Pavlovian conditioning and leaves children with a fairly tenuous grasp on their self-esteem. Children reared in this way often find their sense of self-worth hinges on the approval of others, creating a person not unlike Sophie: outwardly successful, but inwardly pained.

Type B children are well-adjusted for today’s world, while Type A and Type C children adopt alternate strategies to assure attention from their parents. These strategies are initially adaptive, meaning they improve a child’s ability to form attachment relationships with their caregivers. But as children grow, those once-advantageous behaviours of infancy become trap doors of childhood. These trap doors swing open perilously beneath their feet as they attempt to navigate their widening social and emotional landscape.

For Type A children, this means that indifferent behaviour in infancy can lead to excessive people-pleasing in childhood, promiscuity in the teenage years, and an externally assembled adult self, in which the individual’s entire personality is derived from his or her interactions with others. Externally assembled individuals equate praise with self-worth and criticism with self-hatred. Their self-esteem is as capricious as a flag in the wind, held aloft by the breeze and changing direction with each passing gust or zephyr. For Type C, the path embraces contrasting yet ultimately connected aspects of internalizing and externalizing behaviour, ranging from aggression and passivity in milder forms to sadism and seduction, and finally, in extreme forms, rabid paranoia.

We can see these trends in Sophie, a classic Type A child, and Sandra, a typical Type C. Both are haunted by their past, but each woman’s burden takes a distinct shape. Sandra suffers more overtly, her fractious behaviour making relationships difficult and sabotaging her education, leaving her unequipped to function in society. Ostensibly, Sophie did much better. Type A individuals are often outwardly successful people, as their need to please others and thirst for self-sufficiency and approval find natural outlets in career-building. But their drive comes at a price. Type A people find it extremely difficult to trust others, yet at the same time desperately seek their positive regard. We saw as much in Sophie, whose successful teaching career masked the many psychological issues festering beneath the surface: her obsessive people-pleasing, her postpartum depression, and her recurring bouts of crippling anxiety. A harsh word from a student or colleague would slice her to the bone.

Mind you, not every Type A or Type C child will stray to the corrosive fringes of this continuum. Neither Sophie nor Sandra is doomed to a life of rabid paranoia; with professional help and family support, they may even grow more secure over time. Patricia Crittenden’s Dynamic Maturation Model of Attachment eschews rigid boundaries of “normal” and “abnormal.” A person can veer a little to either side their whole lives and still be okay. Nor will their attachment strategy necessarily remain in any one place on the continuum. No developmental authority stamps “Type A” or “Type B” onto one’s baby-self psyche, neatly categorizing the individual for life. Crittenden’s model emphasizes fluidity and movement, as seen in its popular depiction as a wheel. Type B balanced comfortably at the top, a buffer on either side. Proceeding clockwise brings you farther into reactive/ambivalent Type C territory, while moving counter clockwise elicits more and more avoidant Type A behaviour. Go too far in either direction and you wind up at the bottom of the wheel, in the dark and vicious mires of psychopathy.

Mary Main, on the other hand, takes a more rigidly defined, categorical approach to attachment theory. In place of Crittenden’s fluid extremes, she created a separate attachment category altogether, called disorganized, or Type D. Disorganized attachment is, somewhat paradoxically, the strategy of having no strategy at all. According to Main, it occurs when children perceive their parents as aggressive or frightening figures, but also as their only source of comfort and security. The schism produced by these conflicting perceptions breeds confusion, anxiety, and, ultimately, what appears to be disorganized attachment.

Crittenden and Main would probably diagnose Sophie and Sandra the same way, but would butt heads over how to classify Darren. Main would consider him an obvious Type D, while Crittenden would place him somewhere far along the Type C end of the behavioural spectrum.

This might seem like a fairly small point of contention, but it has placed a divide not just between the two theories, but between their major proponents. Crittenden’s Dynamic Maturation Model has been castigated as an unfounded corruption of Ainsworth’s original theory, while Main’s disorganized attachment has been described as a lazy catch-all for behaviours that, ultimately, adhere to either Type A or Type C strategies. And that, really, is the crux of the matter. According to the Dynamic Maturational Model, all attachment behaviour is “organized,” in that children invariably interact with their caregivers in a manner they deem most conducive to their survival. These strategies, though damaging in the long run, are not mere aberrations. They exist for a reason. Even in infancy, children know to look out for number one.

Now any parent whose young child has managed to lay their hands on a pair of scissors, or toddled gleefully toward a busy road, or reached idly for the handle of a pot of boiling water will regard this claim with understandable incredulity. Children, especially young ones, are walking maelstroms of calamity. However, this behaviour stems not from a deliberately foolhardy or self-destructive impulse, but from incomplete neural development. Their little brains simply haven’t matured enough to properly assess risk. Yet even infants know enough to know they’re helpless, and that their survival depends wholly on their ability to charm the enormous, benevolent, and deeply strange creatures that have thus far deigned to feed and clothe and shelter them. Human babies can’t rely on their wits or speed or protective poisons or appendages; they lack any conventional means of self-defence. Their only chance of surviving those tumultuous early years is to forge a bond with their caregivers strong enough to keep them out of harm’s way.

Children will adopt whatever behaviour will best serve them in those first few years where they have only the tiniest modicum of control over their lives, even if it causes innumerable problems for them down the road. This idea is the underpinning principle of the Dynamic Maturational Model. In Patricia Crittenden’s view, all attachment behaviour is adaptive — while an infant may be classified as insecure in the DMM, that child has adapted perfectly to its environment. Mary Main, on the other hand, believes that children do sometimes get it wrong, and in situations of extreme and unrelenting stress, they may behave in a reckless, irrational, and detrimental way.

Which side do we take in this particular feud? As our stance on nature versus nurture should indicate, we aren’t much for “sides.” Our opinion is that, as is often the case when two theories are presented and neither can be easily discredited through observation or analysis, the truth lies somewhere in the middle. Which does not mean both Crittenden and Main are half wrong — both of their views may be correct. They would simply, in that case, be incomplete. Like two artists standing on either side of an object, each puts metaphorical brush to canvas and reproduces with skilled strokes the object’s dimensions, colour, texture, and features as they see them. Both artists paint a stunning picture, reproducing the object perfectly while completely ignoring any aspect of its opposite side. Their paintings may look entirely different, but the object displayed on either canvas is one and the same.

So, in short, we take neither side. We see no practical reason why we should have to. Despite their disagreements, Crittenden’s and Main’s theories are not all that different from one another. Both emphasize the influence of early child behaviour on adult development; by extension, both focus almost exclusively on nurture. Their reasons for doing so are not unfounded — both theories are backed by extensive research showing strong correlations between parenting style and child attachment behaviour. Among the general population, roughly 15 percent of children display some characteristics of disorganized attachment (or what Crittenden would refer to as extreme Type A or C attachment); among maltreated children, that number is 80 percent. Clearly parents have an enormous influence over how their children learn to deal with other human beings — after all, they are the ones on whom children first hone their social skills. However, a small but growing body of research suggests that, though they may sometimes have to shout to be heard, genes still manage to get their say.

The Return of the 7-Repeat

Van IJzendoorn and Bakermans-Kranenburg turned their attention once again to the DRD4 7-repeat allele, although this time they were interested in different child outcomes. Knowing 7-repeat’s influence on externalizing behaviour, the two researchers believed the troublesome allele may hold similar sway over disorganized attachment. But 7-repeat can only increase a child’s susceptibility to behavioural disorders; it can’t actually cause them. An environmental factor must also be at play, and it needn’t be anything as extreme or deplorable as physical or mental abuse. Bakermans-Kranenburg and Van IJzendoorn thought a shift in parents’ mood brought on by recent emotional trauma would suffice.

What sort of emotional trauma? Feelings can be hard to measure, as subjective and messy as they are, which is why Van IJzendoorn and Bakermans-Kranenburg set far more specific guidelines for inclusion in their study. They recruited 85 mothers who had recently lost a friend or relative, someone who they either a) lived with or b) visited at least once a week, prior to the loved one’s passing. Van IJzendoorn and Bakermans-Kranenburg videotaped the mothers as they went about their day, much as the two researchers had done in their externalizing behaviour study. They also conducted extensive interviews with mothers, asking them about the nature of their recent loss, their memories from childhood, and the state of their current relationships with friends and loved ones.

The videotapes were scrutinized, their contents parsed for three distinct classes of actions, deemed “frightening behaviours”: threatening behaviour, frightened behaviour, and dissociative behaviour. These three categories compose a scale designed by attachment theory proponent Mary Main, and together they quantify the degree to which a mother’s behaviour can potentially disturb her child, creating the conditions that cause disorganized attachment. In order to use the scale, researchers observe tapes of the participants and pick out every incident, however minor, that can be classified as threatening, frightened, or dissociative in nature.

Despite their ominous names, frightening behaviours are not necessarily abusive. Threatening behaviour includes scolding, shouting, and spanking. Frightened behaviour is exactly what it sounds like: a mother responding in an emotional or dramatic way to a threat their child doesn’t comprehend, such as a snarling dog, a high ledge, or a busy road. Dissociative behaviour is perhaps the most abstract, and includes any behaviour that separates a mother from her children mentally but not physically, be it a daydream, a trance, or simply a few minutes spent ignoring them in favour of watching television or reading a news article. None of these actions fit our romanticized image of what a perfect mother — that flawless, mythic, Stepfordesque creature — would do, but if a woman invited us up to her apartment and we saw her scold her child for scribbling on the walls, or let out a shriek when she noticed him poking experimentally at an electrical outlet, or tune out his crying while she finished making a cup of tea, we probably wouldn’t feel obligated to call Child Services.

Next, Van IJzendoorn and Bakermans-Kranenburg tested the children when they were between 14 and 15 months old. Each child underwent the Strange Situation Procedure, a test developed by Dr. Ainsworth — Mary Main and Patricia Crittenden’s mentor — to gauge infants’ attachment strategy. The test itself is fairly simple. Researchers subject children to a series of mildly stressful events and record their reactions. Before you recoil at the thought of infants as unwilling participants in some traumatic experiment, we should stress the mild aspect of “mildly stressful events,” which include having an adult the child doesn’t know walk into the room, allowing the child to explore the room on his own, and separating the child from his parents for a five-minute period.[23] Trained observers interpreted the children’s responses to the test and placed them in one of the four attachment categories we discussed previously: secure (Type B), avoidant (Type A), reactive/ambivalent (Type C), or disorganized (Type D). Type B children enjoyed exploring the room. They sometimes became unsure of themselves or frightened, but when they did they found comfort in the arms of their parents, were easily consoled, and happily resumed explored shortly after. Type A children enjoyed exploring, but did not seek comfort from their parents, even when frightened; mostly, they acted as if their parents weren’t there. Type C children hated exploring. They clung to their parents, terrified and inconsolable.

Type D children were harder to classify, as disorganized attachment takes many shapes. Children suffering from it run to their parents for comfort, only to fall silent and turn their heads away. They cringe at their mother’s touch, smile, and claw violently at her face, all in the span of a single thought. They wander the room like shiftless ghosts, ignoring cherished toys and seeking comfort from the walls or furniture. They freeze, fuss, fidget, twist their limbs about in a ceaseless, obsessive-compulsive rhythm, or move as if underwater, stepping and flailing in slow motion. Their behaviour is varied and unpredictable, but bespeaks confusion, anxiety, and profound inner turmoil.

Observers watched for such behaviour, and ranked the children who exhibited it based on the severity of their symptoms. Though the Strange Situation Procedure is designed to allocate children to one of the four attachment groups — Types A through D — Van IJzendoorn and Bakermans-Kranenburg were only interested in whether or not children were disorganized. Type D (disorganized) children were thus assigned to one group, and Type A, B, and C children were lumped together in another.

After sorting through the data, Van IJzendoorn and Bakermans-Kranenburg didn’t seem to have found much of interest, except that older mothers were more likely than younger mothers to raise Type D children. Beyond that, there appeared to be no meaningful correlations between the variables at all. In spite of previous evidence linking maternal frightening behaviour to infant disorganized attachment, the study found no such connection. Disorganized attachment seemed almost random in distribution, as if abiding by rules lying outside the purview of both genes and environment.

The answer lay in the maternal interviews. Unlike the videotapes, which documented specific observable behaviours in mothers (the “frightening behaviours”), the interviews rooted beneath the surface. Through meticulous questioning, Van IJzendoorn and Bakermans-Kranenburg psychologically assessed each mother to determine whether or not she had successfully come to terms with her loved one’s passing. This was not to say mothers no longer missed the departed or felt sad at the thought of them, but that they had passed through the five stages of grief and were able to move forward with their lives. These mothers were classified as having a “resolved loss.” Mothers with unresolved losses, on the other hand, had not yet moved forward. Grief held them in thrall, keeping them from discussing the event rationally or without jarring emotional outbursts. Unresolved mothers provided bizarre or contradictory details about their lost loved ones, muddled their tenses (speaking of the deceased in the present tense; i.e., “Mary likes flowers”), or suffered significant lapses in memory. Van IJzendoorn and Bakermans-Kranenburg placed resolved mothers in one group and unresolved mothers in another, and compared the prevalence of infant disorganized attachment in each.

The discrepancy was stark, and it hinged, as always, on the DRD4 7-repeat allele. Without the 7-repeat, children showed signs of disorganized attachment at roughly the same rate, regardless of whether or not their mothers’ losses were resolved. Among children with the 7-repeat it was a whole different story. In their case, having a mother with an unresolved loss made them almost three times as likely to exhibit signs of disorganized attachment as 7-repeat children whose mothers’ losses were resolved.

Van IJzendoorn and Bakermans-Kranenburg’s findings are surprising. Both logic and past evidence suggested that mothers’ frightening behaviour should be far more influential to their children than their private, inner pain. If anything, frightening behaviours were thought to be how that pain manifested itself — even if unresolved loss was the disease infecting children with disorganized attachment, frightening behaviours were supposed to be the syringe that injected it. But Van IJzendoorn and Bakermans-Kranenburg’s study suggests that children see beyond simple cause and effect — Mom shouts, Mom is upset; Mom spanks me, Mom is angry — and pick up on behavioural quirks so subtle that Van IJzendoorn and Bakermans-Kranenburg needed to implement psychiatric assessments to unearth them. Perhaps children are more perceptive than we give them credit for. Or perhaps our measurement of parenting behavious and attachment strategies is too imprecise.

These are, of course, only the findings of a single study. But Van IJzendoorn and Bakermans-Kranenburg’s experiment underscores the limitations of our understanding. They question the parameters of our knowledge of genetics, psychology, and child development. They prove that the lens through which we watch children grow, as refined as it might be, is not yet fine enough. Above all, they teach us to question our assumptions and look deeper into the ways that our children’s genes and environment interact.

The Broken Filter

For years, the prevailing metaphor for genes was “the blueprints of development,” a master plan on which every facet of an individual is meticulously drafted. The image fit nicely with the predominant theory of genes at the time, called the genetic dogma, which stipulated that the flow of information from DNA to RNA to polypeptide chains to protein is unidirectional and irreversible. According to the genetic dogma, DNA is strictly read-only; RNA cannot rewrite it, nor can a protein be translated back into RNA. However, the latest research shows top-down, dictatorial genetic dominance to be an incorrect, or at least incomplete, characterization of how genes work.

As important as genes are, they are not the only plan from which a person is built. DRD4, 5-HTTLPR, and BDNF are not genes “for” anything more than the products after which they are named (dopamine receptors, serotonin transporters, and brain-derived neurotrophic factor, respectively). These products can, in turn, regulate physiological and mental development, but there’s a lot of give and take between genetic and environmental factors. The environment works in conjunction with genes, and through changes to the epigenome (a process we will discuss in greater detail later), it can actually influence when and how these genes are expressed. Nor are these influences always obvious or simple. Think of the cumulative effects of the 5-HTT and BDNF genes, or the protective properties of a friendly adult outside of the family, or the ability of children to ignore their parents’ dramatic behaviour while latching onto their inner turmoil. Through the course of this chapter, we’ve learned how ineffably complex and muddled and messy child development can be. Beneath the surface, where nature and nurture spiral, clash, and converge, the concept of anything as neat and orderly as a “genetic blueprint” seems trite, or even absurd.

As scientists became aware of this discrepancy, they adopted a new image: the genetic recipe book. As a metaphor, it is more accurate than the genetic blueprint, as it suggests a set of guidelines that rely on the availability of select ingredients and remain open to a certain degree of flexibility. More importantly, following a recipe creates a product greater than — and distinct from — the sum of its parts. After baking a cake, one cannot pick it apart and prescribe one line or word of the recipe to each individual crumb. The recipe metaphor also concedes some influence to environmental factors, rather than supposing that genes alone dictate the end result. The ingredients may combine correctly, but set the oven to the wrong temperature and the cake will be burnt or underdone.

But even the genetic recipe seems somehow insufficient. It implies a clear and straightforward relationship between genes and environment, one that can be easily replicated by following a few basic instructions. Mix thoroughly to combine ingredients. Apply leavening agent to make baked goods rise. Cook at 400 degrees for 35 minutes, or until golden. It’s too neat, too easy, too comprehensible.

Perhaps genes are too sprawling and complex an idea to be housed in a single metaphor. In that case, we propose a more modest analogy, one that focuses specifically on the gene-by-environment interactions we’ve explored in this chapter. When considering the interplay between genes and the environment, think of a gene as a filter, and the environment as a stream of water passing through it. Should the stream contain some debris — anxiety, obesity, behavioural difficulties, and so on — a functional filter will strain out the impurities. Similarly, a broken filter can cause no harm, should the stream itself be pristine. However, when the water is murky and the filter malfunctioning, environmental pollutants will pass through unrestricted, causing a great deal of trouble for the unlucky individual swimming downstream.

We’re fairly fond of this image, we must admit. But it does place a value judgement on various filters, and that can lead to problems. Remember Joey and Erika from chapter 4? If the broken filter theory is correct, it would suggest that their brains were built from inferior genetic material. Joey’s defiant anger and Erika’s depression may be the result of troubled home lives, but with better supplies of serotonin or dopamine, their symptoms never would have appeared in the first place.

Therein lies the theory’s main problem. If one filter is functional and the other is broken, then one gene is clearly better than another. And if that is the case, why has evolution not selected against the “broken filter” genes? They are not recent mutations — we can find examples of them in almost every animal on earth. Surely such a glaring genetic defect couldn’t survive a billion years of natural selection if it didn’t also carry an equal or greater advantage.

Perhaps our metaphor needs work. What if, instead of a broken filter, we simply had one with looser, more permissive netting? Such a filter wouldn’t do as good a job of catching debris as would a more stringent model, but it may also permit the passage of beneficial materials — nutrients, for instance — that the more functional filter would block. In this case, one filter would not be invariably better than the other. Instead, each would be useful in one environment and detrimental in another. Perhaps, if raised in more supportive environments, Joey and Erika would not only recover, but excel. Their permissive filters,

completely unsuited to troubled environs, would suddenly become a tremendous asset. Such a concept would radically recontextualize the findings we’ve discussed so far, necessitating a lot of research, several well-designed studies, and a revolutionary new theory of gene-by-environment interactions.

For this, we turn to a man named Thomas Boyce.