BOOKS:
Unique, Like Everyone Else

By Amy L. Wax

Amy Wax on No Two Alike: Human Nature and Human Individuality by Judith Harris

Judith Harris.
No Two Alike: Human Nature and Human Individuality.
W.W. Norton & Company. 322 pages. $26.95

Consider your pre-teen son: A cocky, boisterous techno-geek obsessed with computer games, puzzles, and conspiracy theories. A master procrastinator who has been known to blow off school assignments. Loves to sleep late and stay up all night. Covets designer shirts, big houses, and fancy watches and recently announced his plan to buy his future wife “a big, beautiful, expensive diamond engagement ring.” Touts the virtues of free markets, low taxes, and making lots of money. Is the messiest person on Earth.

Now about his parents: A reticent bleeding heart liberal married to a diffident Luddite. A lifelong neatnik and a morning person. Both conscientious and punctual to a fault. Never procrastinate, hate games, and don’t truck with conspiracy theories. Prefer small spaces. Have never owned, bought, or desired a diamond ring.

What went wrong? According to Judith Harris, nothing. This is the way it’s supposed to be. But it’s not as bad as it sounds. Your son is smart, curious, precise, candid, opinionated and shrewd. In other words, just like his parents! As Judith Harris further explains, that’s the way it’s supposed to be too. Children tend to resemble their parents. But only up to a point. Beyond that point, they tend to be very much themselves.

What accounts for the similarities and the differences? Harris’s task in her controversial first book, The Nurture Assumption (W.W. Norton, 1998), and its sequel, No Two Alike, published this year, is a formidable one. She seeks to explain nothing less than the mystery of what makes people different from one another — and from the very people who raised them. There’s only one of each of us. No two are alike. This is such a commonplace of human existence that we hardly think about it. Although the individuality of each person is taken for granted, understanding the forces that shape each person’s peculiar combination of traits, quirks, talents, and tastes is a key challenge for social science.

That project belongs to developmental psychologists. Harris is not one of those. Rather, she is the quintessential outsider — a person with no official position and, until recently, no status within the field. Although she tried to join the club by enrolling in the doctoral program at Harvard, she was asked to leave graduate school because of her lack of “originality and independence.” A chronic illness soon forced her into a homebound existence. Her offer to help a friend rewrite an article led to a career writing psychology textbooks. For a new text designed to integrate insights from biology and developmental genetics, she embarked on an ambitious and comprehensive reading project — a venture most academic “experts” are too busy to undertake. The project produced her “Eureka!” moment. Harris perceived that the wisdom she had been dutifully digesting and restating for years in texts used by psychology students around the country was at best highly dubious and at worst patently misleading. The emperor’s clothes, although not altogether absent, had some very large holes.

Her conversion experience produced a professional-quality article that set out a sweeping critique of established methods and assumptions in the field of human development and proposed a new theory of how individual personalities emerge. To the psychology profession’s credit — and despite her merciless skepticism about the work of key researchers — her piece was awarded the George A. Miller prize, named after a venerable professor at Harvard who, to Harris’s delight, was the man who had signed the letter asking her to leave Harvard graduate school many years before.

Harris’s article asks “Where is the Child’s Environment?” As she stresses repeatedly in her books, answering that question — and figuring out how experience shapes the person — requires confronting how biology affects behavior. As she puts it with her usual unsparing bluntness, “without a method for controlling for the effects of genes, research on human behavior is useless.” For most of the twentieth century, too many psychologists ignored this lesson. Only a few — like the eminent behavioral geneticist Robert Plomin, whom Harris clearly venerates — made it the foundation of their research. For the most part, developmentalists were content to assume a causal connection between observed childrearing practices and children’s outcomes. Rarely did they expressly consider — let alone rule out — an alternative possibility: that the environment at home may not matter and that shared genes independently influence how both parents and children behave. The result of that omission was a literature rife with dubious and unsupported findings and ripe for a revisionist critique.

Toward those who ignore the potential role of genetic influence, Harris is unforgiving. Yet the belief that parental nurture determines how children turn out, which has occupied the status of unquestioned orthodoxy for so long, is understandable. Children do resemble their parents, and close family members are significantly more alike than strangers chosen at random. The similarity emerges both in how parents act and in how their children act in turn. The children of articulate parents tend to be well-spoken. Impulsive, violent parents produce children prone to violent and anti-social behavior. The progeny of divorced parents have trouble with their own marriages, and are more likely to divorce as well.

As Harris reminds us, however, it doesn’t follow that what goes on in the home is the reason for the resemblance. Correlation is not causation. For every observed similarity we must ask: Is it rooted in upbringing, or does it follow from heredity? The genes parents share with their offspring may account for the way parents behave as well as for how children respond. On this view, it’s not domestic violence or corporal punishment that produces violent children, nor is it communicative parents that create expressive kids. Growing up in a broken home does not cause children to have unstable adult relationships. It’s that parents pass down to their children the genes for violence, or verbal acumen, or difficulty getting along with others. It doesn’t matter how your parents raised you. It matters who they are genetically.

Although genetic endowment must be taken into account along with home environment, why choose between these two? Don’t nature and nurture both matter? It turns out that both do. Behavioral geneticists’ best estimate from population data is that each contributes roughly 50 percent to the main elements of personality. But then isn’t the answer that parental influence runs both through genes and environment? That’s where Harris’s key contribution comes in. From her survey of the main studies in behavioral genetics she concludes that although genetic endowment looms large, how parents behave makes almost no measurable difference. Individuals are partly the product of their experience, but the experience that matters is not to be found at home.

Her conclusions are drawn mainly from the literature on twin “cross-fostering” studies. That body of work uses statistical techniques to take advantage of a natural experiment. Twins and siblings are sometimes adopted out to different families. By comparing large numbers of siblings reared apart to those reared together by their biological parents, and taking into account siblings’ or twins’ degree of genetic relatedness, researchers can tease out the influence of the home environment on various measures of personality and behavior. The results of such population studies are surprising. For a broad range of traits, siblings reared together in their native home are no more alike than siblings adopted out and reared apart. And, regardless of how they are reared, siblings resemble each other only as much as their shared genetic inheritance would predict. The same results obtain for fraternal and even identical twins. (Full biological siblings and fraternal twins, on average, share half their genes. Identical twins share all.) In fact, after accounting for genetic resemblance, siblings and twins are no more similar than people randomly drawn from the population. Growing up in the same household and being exposed to the same parenting don’t seem to add to the effect of having the same biological parents (as with siblings) or the same genes (as with identical twins). In sum, the data show almost no role for “shared environment,” which is the term for the childrearing milieu that parents create and that children reared in the same home have in common. How parents raise children seemed to matter very little, if at all, to their adult personalities. The “environmental” portion of children’s individuality comes from somewhere else — what geneticists have dubbed the “non-shared” environment.

In The Nurture Assumption, Harris turns her attention to this “non-shared” experiential component of how children turn out. If parents aren’t providing the key inputs, then who or what is? Harris’s answer, in short, is the peer group. As long as human beings have been on Earth, small children have remained close to their mothers for a limited period. For most of history, the exigencies of repeated childbearing pushed children into the communal play group almost as soon as they could walk. That basic pattern still remains. Although small children stay with their parents, they soon look to their friends. Peer groups have their folkways and practices, which quickly eclipse parental influence. Harris’s notion that playmates are more responsible than parents for the environmental half of development is both intriguing and original. The few examples of peer influence she provides, including language acquisition and ideas about sex roles and behavior, are familiar and persuasive. Children educated in a foreign country learn the language and pick up the local accent with lightning speed. School-age children rigidly segregate by sex and tenaciously endorse “gender stereotypes” despite their parents’ best efforts to discredit their validity.

But the peer influence hypothesis is not without its difficulties. For one thing, it suffers from vagueness. At times, and depending on the behaviors at issue, Harris expands the “peer group” to include the neighborhood or “the broader culture” — more amorphous and muzzier categories that make it hard to take the measure of her claims. For another thing, her conclusion that parents are of no consequence leaves many questions unanswered. What The Nurture Assumption never gets around to addressing is why, once genes are factored in, siblings and twins, whether reared together or apart, differ so much and so randomly from each other. After all, if they’re exposed to the same peer group or neighborhood or culture — if they share the “nonshared” environment — they should turn out pretty much alike. So how do we explain that in many important respects they don’t?

That is the puzzle Harris takes on in No Two Alike. Here she outlines a theory of how each person becomes a unique self. Why does one twin turn out (relatively) confident and the other timid? Why is one brother impulsive and the other methodical? How does a child come to prefer pushpin and her brother poetry? Behavioral genetics has given the logic of nonshared — that is, nonfamilial — influence relatively little sustained attention, so Harris’s answers are necessarily speculative. Her analysis begins with a quote from Thomas Jefferson, who said: “I consider man as formed for society, and endowed by nature with those dispositions which fit him for society.” According to Harris, the tastes, inclinations, and traits that we adopt in the course of growing up can be understood as responsive to the intricate necessities of negotiating the social world.

Harris divides the main tasks of social life into three categories, corresponding to three complex interactive systems. These systems, which are deeply rooted in human nature, relate to the demands of surviving in a communal setting. Most broadly, we must become socialized. We must learn the rules for conveying social meaning and the conventions for getting along with others. More specifically, we must develop relationships and learn how to forge and preserve ties with those who matter to us and who critically affect our well-being and survival. Finally, we must grapple with the status system, which assigns our place in the pecking order and fixes how much influence we exert or experience from others. In myriad episodes, from trifling to momentous, that mark our path from immaturity to adulthood, we are repeatedly jostled by our encounters with others — encounters that are often random, unpredictable and outside our (and our parents’) control. We happen to come under the wing of a loving (or harsh) mentor or teacher, receive a hoped-for (or disappointing) response to a social overture, or fall in with a group of children who are taller (or shorter), stupider (or smarter), less (or more) studious, or ambitious, or reckless than we are. We deal with these experiences through trial and error, using stock strategies and behavioral ploys. The outcomes of these experiments gradually shape our emotional landscape and form our habits for responding to others. From the accumulation of these chance encounters unique personalities emerge. Thus, even if two persons start from a common bedrock of tendencies and abilities  — their shared genetic inheritance — they soon diverge. Life takes them by increments down very different paths. Your peculiar combination of zigs and zags will never precisely mirror your sister’s — or your twin’s. You may start out very close together, but the long road to adulthood can take you very far apart.

Is Harris’s theory of individuality right? By her own admission, her account is highly speculative and awaits testing by others. She suggests, however briefly, that using some of the newer brain imaging techniques to monitor “the activation of different mental processes” — including those identified with one or another of the three social systems she describes — might prove revealing. She also recommends taking advantage of “natural experiments” by seeking out people who are “selectively weak in one or more” of the functions of socialization, maintaining relationships, or negotiating status. Beyond these sketchy and inchoate proposals, however, she leaves verification to others.

Despite the tentativeness of some of her theories, Harris’s books are well worth reading for many reasons. With its roots in old-fashioned curiosity and wide learning, her exposition is a tour de force of arresting anecdotes, lively reportage, and lucid analysis. Her picture of the vagaries of psychological science and the rivalries of academia, which is not always pretty, invites a healthy skepticism. Her contrarian relish for demolishing weak arguments and unmasking shoddy research provides a bracing antidote to the credulous psychobabble that fills the popular media and too often finds its way into academic journals. Above all, her books are valuable as a reminder of the core insight from which they proceed: Never assume a role for nurture without first ruling out nature.

Harris is also revealing on why science resisted this lesson for so long. Her account suggests that the culprit was equal parts methodological laxity and ideological fervor. Fueled by psychoanalytic assumptions and wary of genetic “essentialism,” researchers were more than happy to parlay a few poorly controlled clinical observations into an elaborate list of guilt-making, childrearing “dos and don’ts.” At the extreme, this exercise produced some of the most cringe-worthy howlers of the twentieth century: Emotionally cold mothers cause schizophrenia and autism. Ineffectual fathers produce homosexual sons. Early toilet training and parental rejection fuel depression, neurosis, and low self-esteem. Compulsive mothers lead to anorectic teenagers. Science has thankfully defeated some of these notions. We no longer think that parenting style has much to do with schizophrenia, autism, anorexia, or homosexuality. Investigations into brain anatomy and neurochemistry and greater appreciation of the role of genetic endowment have undermined the tendency to “blame the parents” for these conditions. Yet how parents raise their children is still deemed responsible for many of those children’s disappointments and shortcomings, from extreme shyness to failure to get into the Ivy League.

As experience with some of the more discredited notions reveals, an uncritical focus on parental nurture is hardly value-free. The reflexive tendency to see parenting as all-important has distinct social consequences and jibes with a particular cultural agenda. The idea that parents can control what children become is at odds with recognizing that genes influence behavior and fits best with a thoroughgoing social constructivism. That people are fully the product of their environment is also linked to an egalitarian agenda that invites sweeping social engineering, sees human nature as fully malleable, and promises the eradication of key disparities.

The vulgar version of radical environmentalism that assigns parents a make-or-break role in children’s lives also has a dark downside. Blaming parents often translates into blaming mothers. The toll on women can be extreme. As Judith Warner and others have documented, never before has motherhood been such a high-stakes game. The resulting frenzy, which leaves many mothers exhausted and stressed to the limit, may even contribute to the low birth rate, especially among those superachievers most caught up in the drive to maternal perfectionism. Above all, the parental arms race makes it harder than ever for women to combine motherhood with a demanding career. A signal irony of the leftist Zeitgeist is that an exaggerated belief in the power of parents is on a collision course with feminists’ worldly ambitions for women. So much for the cultural contradictions of constructivism.

Fueled by her conviction that, short of wild aberration, parenting doesn’t really matter, Harris barely hides her contempt for know-it-alls who purport to tell us how to raise our kids. She insists that predictions about how children will respond to a given approach to parenting, which are the staple of legions of advice books, are pure myth. The “interactionist” insight favored by some developmental psychologists — that particular parental strategies may act on some children’s genetic tendencies to produce specific outcomes — is too abstract to offer any help. Without identifying the genes and knowing the precise rules of nature-nurture interaction, we simply can’t develop meaningful guidelines for pushing behavior in the desired direction. Or, as Harris puts it, quoting developmentalist Thomas Bouchard, “How non-traumatic environmental determinants influence the normal range of variance in adult personality remains largely a mystery.” Her advice to parents: Within the wide berth of what passes for normal childrearing, just muddle through.

Nonetheless, the notions that children’s traits are exquisitely sensitive to parental nurture and that parents can shape their children’s personalities in systematic and meaningful ways retain remarkable vitality among experts, popularizers, and, of course, parents themselves. Are we all just in the grip of a delusion? Can all those people be so very wrong? A more careful reading of Harris’s book suggests that the errancy is not quite as egregious as she sometimes implies. For all her virtues as an honest broker of the scientific literature, she occasionally overstates. There is a disconnect between some of her more provocative rhetoric and passages that, however briefly and coyly, admit that parental influence is not a complete chimera. Home environment does sometimes make a difference.

Ultimately, the best reason to approach Harris’s position with caution is that, although her review of developmental science purports to be comprehensive, the science itself is not. A good deal of the literature that seeks to disentangle nature from nurture addresses the development of personality. But this field is not without considerable limitations.

A standard paradigm for rigorous empirical study within developmental psychology is the “big five” model, which rates people on the traits of extroversion, conscientiousness, openness to experience, emotional stability, and agreeableness. But this scheme is no match for the richness of human complexity, which encompasses a far longer and more nuanced list of attributes. Conscientiousness, for example, comprises six elements: achievement striving, competence, order, dutifulness, self-discipline, and deliberation. Extroversion includes friendliness, warmth, empathy, aggressiveness, and dominance. Not all of these cluster together, and some may be in tension with others. But when it comes to social science, subtlety and statistical significance make uneasy bedfellows. Multiplying factors to capture true differences renders research cumbersome and expensive and undermines validity. Not surprisingly, neither the relationship of numerous personality variables to life outcomes nor the importance of home life to each has been fully explored. Without a more careful dissection, it’s dangerous to say that parents cannot meaningfully shape the behaviors that really matter most to happiness or success.

More important, personality traits do not remotely encompass the whole person or exhaust everything parents (and societies) really care about. Within the very broad range that passes for normal, the aspects encompassed by the “big five” may cause delight, dismay or annoyance. But do parents lose much sleep over whether their kids are shy or gregarious, spontaneous or rule-bound? Although conscientiousness has been shown to bear on job success, the remaining traits don’t seem to skew life outcomes in any significant or systematic way.

The same cannot be said for other qualities. First among these is cognitive ability as measured by iq testing. In our technological, status-crazed, career-oriented society, intelligence is paramount. But iq is also the elephant in the room for any theory that identifies genetic endowment as critical and parental nurture as inconsequential. The problem is not so much that individuals differ, but that groups do. The average iq for blacks is significantly lower than for whites, and Asians exceed both. What are we to make of the origins of these differences?

Not surprisingly, Harris treats iq with kid gloves. She leaves no doubt that she believes biology plays a significant role but veers away from directly ascribing group differences to genes. Harris is brief and somewhat equivocal on the contribution of nurture to intelligence and on whether parents matter. On the one hand, she describes cross-fostering studies that show that, as with personality, family environment is unimportant: Although adoptive parents transiently influence their children’s intelligence, identical twins reared apart ultimately converge in iq as they grow older. Likewise, groups of biologically unrelated adoptive siblings reared by the same parents gradually diverge in intelligence and show no correlation. But elsewhere, Harris admits that iq differences — including average differences by income and race — emerge quite early, before children interact with peers or are exposed to the broader environment. The problem is that if genes don’t explain these group differences, they must originate within families — that is, parenting must influence iq. To avoid the unpalatable conclusion that group differences are due to genes, Harris concedes at several points that features of the home — such as how parents converse with children and how often they read to them — do appear to affect mental abilities. In other words, parents do matter. She adds, however, that parents aren’t all that matter. Home environment, culture, and peer influence are all key inputs for mental ability. And group differences persist because, in our society, all these elements differ systematically across groups.

How does Harris square this account of group differences with the twin adoption studies, which suggest a minimal role for home environment in fixing iq? Harris notes that adoptive parents are predominantly white and middle-class. This “restriction in range” in the population of adoptive parents participating in cross-fostering studies means that adoptive children are not exposed to the cultural variations that would tend to generate systematic iq differences from similar genetic endowments. In other words, the environments of adopted children (and white middle-class children, for that matter) are so similar that intelligence is overwhelmingly determined by genes. The problem with this story is that it conflicts with data Harris doesn’t discuss, including studies showing that black adopted children — even those raised by white middle-class families — have lower average iqs than adopted whites. Harris’s haphazard treatment of intelligence and group disparities allows her to avoid the socially and politically awkward implications of these findings.

The second vexed subject Harris finesses is delinquency. Once again, there are well-documented differences by gender, race, and class in the incidence of antisocial behavior, from juvenile misconduct to adult crime. As Harris notes, it’s not easy to disentangle parents’ role from the effects of neighborhood or peers. Techniques for measuring intelligence in preschoolers allow parental influence to be isolated, but reliable indicators of delinquency do not emerge until after children start school and are exposed to friends and the wider world. Since the reality is such that these influences tend to differ systematically by social class and by race, Harris views the data as suggesting that, for criminal behavior, “it’s the neighborhood, not the home, that determines whether or not a child will become a lawbreaker.” Elsewhere, however, she admits to evidence that “shared environment” — that is, parents — can modulate the risk of adolescent delinquency. In fact, recent studies point to some role for parents, at least at the extremes. Using cross-fostering data, social scientists such as Susan Jaffee at the University of Pennsylvania and Janet Currie at Columbia have shown that although children are generally unaffected by ordinary corporal punishment of the “swat on the bottom” ilk, severe parental abuse or mistreatment enhances the risk that children will get in trouble later in life. In addition, there is recent, striking evidence, based on data revealing the type of specific gene environment interaction that researchers have long been seeking, that children with a particular genetic signature are more vulnerable to the effects of early abuse. All these findings suggest that criminality is a function not just of hereditary factors and peer influence, but of home environment as well.

Finally, additional aspects of the person that are as important, or even more so, to who we are lie beyond the hot-button arenas of intelligence and crime and the well-studied realms of personality. These include tastes, interests, manners, morals, values, speech, demeanor, style, ambition, vision, attitude to risk, self-concept, life goals, eating habits, and those all-important behaviors that constitute character. Harris makes much of acquiring a foreign language and accent, where parents routinely give way to peers. But the question of where parents leave off and peer culture kicks in for other items on this list remains murky. Does our home life really have nothing to do with whether we grow up to say please and thank you, clean up after ourselves, love ballet or opera, aspire to a profession, cheat on our taxes, give generously to charity, betray our country, or become a teenage mother? We don’t know because the data just aren’t there. Until we do, most parents would prefer to assume that the example they set is vital.

Harris scoffs at this assumption as a sentimental delusion. Our culture’s obsession with the vagaries of parent-child interactions is, in her mind, woefully misplaced. But there is one important sense in which parents are right. Harris doesn’t deny — indeed, she agrees — that wholly apart from the home atmosphere they create, parents have a decisive role to play in their children’s lives. Parents exert their main influence by choosing, shaping, fostering, and sustaining the broader cultural milieu in which children grow up. This is not to deny that a key crucible of development is the peer culture, as Harris stresses in The Nurture Assumption. Rather, it means that steering children towards the right peers is critical.

It does indeed take a village, then, and parents — especially privileged parents with the wherewithal and means — are remarkably adept at selecting villages with desirable denizens. Of course, even strenuous efforts can go awry. Peer culture is notoriously mercurial and unpredictable. We know little about how positive group dynamics arise and persist or about how to prevent subversion from without and within. The extent of parents’ power to fend off corrosive influences, especially in today’s media-saturated world, remains uncertain. Harris doesn’t have much to say about these mysteries, except to remind us frequently that, all else being equal, genetic birds of a feather flock together and exaggerate each other’s best, or worst, tendencies.

The most determined parents are nevertheless undeterred by the challenges of choosing and controlling their offspring’s surroundings, however formidable, expensive, and exhausting the task. Many go to extreme lengths to find neighborhoods, schools, playgroups, sports teams, and other institutions that they believe will promote desired attitudes and values. Above all, parents are most concerned to avoid destructive peer influence. Under the guise of a quest for academic quality, the relentless focus on “good schools” is largely a front for avoiding the wrong kinds of kids — kids who carry guns, skip school, blow off homework, scoff at academic achievement, spout profanity, join gangs, vandalize property, lack fathers, bear babies out of wedlock, or have mothers who do. Too often, those kids are also “kids of color,” and the frantic game of parental musical chairs often amounts to “white flight.” More generally, the goal is to avoid the poor, who suffer from enhanced risk of many kinds of dysfunction that could influence the children of those who are better off.

The clear implication of Harris’s books is that parents’ fears of wayward peers are well-founded. One cannot help but conclude that it’s parents’ Job One to discriminate — in the old-fashioned sense of seeking those with shared values and shunning those without. In today’s world, that task is harder than ever. Where desirable peer influence is not equally distributed by race and class, parental vigilance runs up against the imperatives of tolerance and “diversity.” Discouraged from coming out openly for bourgeois values, parents resort to euphemism and shibboleth. But lack of candor doesn’t stop them from doing their job, which is to find the “right” neighborhoods with the “right” schools. When it comes to safeguarding offspring, exit, not voice, is the strategy of choice.

But what of children whose parents won’t or can’t search out the best? They are indeed left behind to live in neighborhoods and attend schools others strenuously seek to avoid. In the wake of Hurricane Katrina, an old idea for addressing this dilemma has resurfaced: social dispersion as a solution to the problems of racial disparity and social inequality. Let’s send poor families into middle-class neighborhoods and their children into good suburban schools where they can assimilate to the dominant virtues of striving, high aspiration, restraint, good manners, and discipline. It should not surprise us that the project of social mixing meets staunch resistance. Well-placed parents are justifiably wary of what happens when children with radically different backgrounds and values come together.

Can a project of social mixing succeed? Overcoming parental resistance will require greater candor and more social realism than has so far marked the debate. The embrace of diversity has costs and dangers as well as benefits, especially in the rearing and education of children. Group customs are fragile and vulnerable to subversion. And, as Malcolm Gladwell has taught us, numbers matter. “Tipping” is sensitive to critical mass, and desirable habits won’t necessarily triumph if too many disruptive kids show up. Even if the numbers are right, the vagaries of peer fashion provide no guarantee that contagion will run in the desired direction. The bad can infect the good as easily as the good can uplift the bad.

Many well-placed parents would rather not admit any of this. They are admirably committed to the rhetoric of equal cultural worth, which resists openly judging some ways of living as undesirable, maladaptive, or dysfunctional. But allaying middle-class parents’ justifiable fears of the poor and minorities — fears they act on but are loath to express — will almost certainly require schools to insist upon an atmosphere that educated parents expect as a matter of course. That means relentlessly suppressing undesirable behaviors. But it also may mean disparaging or even banishing certain “lifestyles” — including ones that are dominant within particular cultures or groups. In the current climate, these requirements are unlikely to be met. It is one thing (and hard enough) to enforce decorum, politeness, and respect for teachers. It is quite another to condemn single parenthood and teen pregnancy, expect middle-class standards of sexual discretion, insist upon refinement in speech, dress, and manners, and unequivocally banish traces of punk and ghetto culture. It’s so much easier for parents of means to withdraw into like-minded enclaves than to do the hard work of setting standards and confronting undesirable behavior. Yet the transmission of cherished values rests on the willingness to take these steps. The paradox in our era of “tolerance” and political correctness is that flight — white or otherwise — has become the parental tactic of choice. Separation by class and race is, if anything, more pronounced than ever.

Although harris’s theory ratifies the soundness of parents’ efforts to locate the best environment for their children, she doesn’t stress that function. Indeed, she doesn’t give it as much play as it deserves. Her agenda and her tone are too fatalistic for that. Her real goal is to persuade us that everyone is his or her unique self precisely because what happens at home is so inconsequential and outside of home so unpredictable. Within the broad outlines of what parents can control, she would bring us back to what is out of their hands. Once offspring venture out of the nest into the wider world, life takes them to unique and unknown places. Science isn’t close to having the tools to trace out these destinations, so the mystery of personality won’t be cracked anytime soon. Indeed, one of the take-home lessons of Harris’s books is how daunting is the task, if done correctly, of investigating human development. Even disentangling the two forms of parental influence (genes and nurture) is impossibly demanding because the cross-fostering studies that are the state-of-the-art method are so cumbersome. Scientists can’t tear children away from their parents at will, so they must await “natural experiments.” Those aren’t very common to begin with, and in an era when few American women relinquish their babies for adoption, the conditions needed for rigorous investigation of all the influences on development will become harder to find. This bodes ill for advancing the state of knowledge in this field.

This very intransigence offers comfort and counsels humility. Despite the hand-ringing about “designer babies” and parents rigging their offspring’s genes, these efforts can go only so far. Our birthright slants our reactions but does not write a fixed and straightforward script. Nature endows but leaves plenty of wiggle room. That we are conscious creatures with intellect, will, and the capacity for self-reflection only adds to the myriad possibilities. In all important ways, we are radically unpredictable. Because our understanding of development is so primitive, the puzzle of who we are will remain firmly in place for a long time to come. As persons, we are left with our dignified individuality and the unplumbed mysteries of human freedom. As parents, we must accept our children as gifts we can neither author nor control. We have no choice but to love them — techno-geeks, procrastinators, diamond-lovers — as they are.