On its face, the idea that early parenting activities could shape the adult whom the child is to become is suspect, even under the strongest tabula rasa assumptions. Thinking of a parent-shaped preadolescent personality as an ordered system, once the external energy of parental control is withdrawn, entropy would tend to disorder the system. This is little more than the statistical fact that the parentally desired result is such a small subset of the possible results that it is vastly unlikely to hold. This metaphor from dynamics suggests a priori that the shaping designs of early parenting are doomed, rather like arranging the pebbles at low tide to form HELP! Or so it has always seemed me.
Yet it is an article of faith within popular culture that, within the range of what is non-pathological, different parenting styles will have different long term effects upon the personalities, achievements, and life choices of adult children. While this idea is not quite so firmly planted in the scientific literature, it has certainly been the dominant assumption within developmental research. In this century, classical psychoanalysis, attachment and critical stage theories, behaviorism, the authoritarian-authoritative-permissive analyses, single parenthood studies, birth order research, spanking studies, and more, have dominated attempts to both understand individual differences, and to correct the pathologies that so often accompany them. All these traditions attribute critical causal effects to parenting styles and home life, often in the child's earliest years. It is this idea, the (early parenting) nurture assumption, that Harris subjects to questioning. Her attack is three pronged: emphasize the effects of genes, emphasize the effects of peer environments, debunk the research on parenting style and home life effects.
Harris' treatment of behavioral genetics is a model of scientific writing. Her discussion of the twin research and its implications for the nurture assumption are very clear and logically very sophisticated. Her explanations of mistaken causal direction, of two-way child-parent causal interactions, and of direct and indirect genetic effects could serve as a logic primer for any consumer of what "psychologists have shown". Harris is too sophisticated to be a genetic determinist. For example, the degree to which a child is accepted by peers (an environmental factor) will affect self-esteem. But here too the causal issue is not so simple. Direct genetic effects such as height, timidity, or physical appearance will affect a child's peer acceptance and could therefore count as indirect genetic determinants of self-esteem. In general, children's direct genetic characteristics will to some degree shape their environments which in turn affect the more malleable aspects of personality and behavior. Whether these latter aspects should be attributed to nature or to environment is an interesting question for causal analysis.
Harris' paradigm of the importance of peer influence in comparison to that of home life is the acquisition by young immigrants of, and preference for, the socially predominant language, even in the face of the parent's unwillingness to learn it. Group influences dominate parental/home influence. Harris reviews a great deal of literature from primate behavior to teen smoking to illustrate this dominance, finally arguing that it is difficult and rare that the family can function as a causally significant group.
Harris' debunking of parental/home socialization research takes the forms of surmised alternative explanations, sophisticated factor re-analyses, citations of contradictory research results, and the presenting of anecdotal personal references. The accumulation of these forms is telling, and is sure to raise doubts in minds that are even slightly open.
There certainly are some knits to pick. First, it is left somewhat unclear what part of the non-genetic influences Harris is attributing strictly to chronological peers as opposed to the more general group characteristics. It seems at times that "peer" is a synonym for "cultural". Second, while Harris' re-analyses of the studies whose conclusions she opposes are astute, she does not apply similar attention to the details of the research whose conclusions agree with hers. An example of this is her argument against the conclusions of the often-cited McLanahan and Sandefur research concerning the supposed ill effects of fatherlessness. Her re-analyses of their results in a way that avoids home life influences are careful and enlightening. But in so doing, she relies in part upon studies that she does not subject to similar scrutiny, displaying a bad case of confirmation bias. Third, if Harris can conceptualize indirect genetic effects of the type mentioned above, the proponent of parental influence should be able to speak of indirect parental effects, the parental power to shape the child's peer groups and more general social environments. This idea merits only three pages in a four hundred page book, yet a great deal of what goes under the heading of parental practice is precisely this. One could name the choice of play groups, neighborhoods, schools, religious affiliations, vacation spots, summer camps, after school activities, and extended-family contacts; or the willingness to pay for cochlea implants, cleft palette repair, expensive sports equipment, musical instruments, lessons, in-style clothing, cars, SAT prep courses, and private college; or decisions concerning after-school jobs, curfews, and unsupervised socializing. In all of these areas it is within the parent's power to shift the child's peer groups and social environments. The effects that Harris is so willing to attribute to these latter factors could just as well be classified as indirect effects of parental practice. Fourth, also escaping Harris' critique of the (parental) nurture assumption are the potentials of direct parent-to-child intervention in times of crisis, for example, of drug use, school failure, the death of a loved one, depression, post traumatic disorders from auto accidents, suicide attempts, and so much more. These crises have the potential to lead the child down paths that could forever alter their lives. Good parenting is more likely to defuse these threats than is bad or neglectful parenting either by sound advice given from a trusting relationship, or the more formal approaches of behavior modification.
But even if the nurture assumption that Harris attacks is limited to claims of the differential personality-shaping efficacy of alternate styles of direct, parent-to-child exchanges, her conclusions are very interesting and contradict much of what is commonly assumed in both the popular and the scientific literature as well as in therapeutic practice. In this sense I am in sympathy with her conclusions and believe that the popularity of this book will have beneficial effects.
Here then are some implications of accepting Harris' conclusions. First, parenting could be reframed more as an attempt to create a human relationship to be valued and enjoyed for what it is rather than as the actions of the child's personal trainer. Second, the evaluation of parenting success would focus on this relationship rather than upon the supposed "fruits" of the activities of child raising. Third, the area of potentially efficacious parental shaping activities would focus more on excluding factors that could derail the child's uniquely natural flourishing than on the introduction of personality contours that don't fit nature's mold. This would have the effect of requiring the parent to find out who the child is (and is not) rather than obsessing about what it would be good for the child to become. Fourth, except in the extreme cases of "toxic" families, parents are off the hook for the usual problems that clients bring to therapists.
These implications are all to the good. I certainly hope that Harris' important work will gain a wide readership.