The nature-nurture war has been all one-sided—inside academia.
The nature-nurture wars have been one-sided when it comes to research—genes matter a great deal and the shared or family environment means very little. Nevertheless, sociologists and psychologists continue to give opinions about how children develop; these are basically just-so stories based on opinion or incomplete research. The No Child Left Behind program is a good example. Genetic differences between races in average intelligence are ignored, even though naïve environmentalists can no longer support the position that genes have zero influence. Mainstream academics commonly agree that the intelligence is 40~60% heritable. Behavioral geneticists place it more accurately at 40% in childhood and 80% at about the age of 25, when development of the prefrontal cortex is complete.
In 1998, Judith Rich Harris published “The Nurture Assumption.” It laid out the position that as children develop, genes plus the unexplained environment (formally known as the nonshared environment), ultimately determined how children differed. The family environment had virtually zero impact in how they turned out by the time they passed through adolescence. She proposed that “children are socialized by their peer groups.”
Since her book was published, some of the most eminent developmental psychologists published “The Relationship Code,” based on a 13 year study of children, sponsored by the National Institute of Health and four universities, entitled Nonshared Environment in Adolescent Development (NEAD). The study confirmed Harris’ hypothesis: that genes and the unexplained environment are the only determinants of the developing personality and intellect. (Excerpts from the book are available here.)
In her latest book, “No Two Alike: Human Nature and Human Individuality,” 2006, Harris builds upon the NEAD study and other research to explain how children build relationships, become socialized, and gain status. (Excerpts from her latest book are available here).
The first half of the book deals with dismissing what Harris calls red herrings. Harris states: “Personality differences…are not mainly due to differences in environment, nor to a combination of ‘nature’ (genes) plus ‘nurture’ (the part of the environment provided by parents). Nor…can they be explained in terms of gene-environment interactions. The remaining candidates were crossed off …environmental differences within the family and gene-environment correlations.
“Five red herrings. None of them can be the solution to my mystery. All make predictions that are inconsistent with the evidence; none can explain the differences between identical twins. But there are plenty of fish in the sea. What about all the other theories of personality development?
“Sorry, they won’t work either. Before you dismiss that statement as sheer chutzpah, listen to my reason for making it. I can eliminate all the currently popular theories of personality development with a single flick of my hand, because they all rest on the same basic assumption about learning. The assumption is that learned behaviors or learned associations transfer readily and automatically from one situation to another. What all these theories have in common is the idea that children learn something in one environmental setting (usually the home), or with one social partner (usually the mother), and that this learning subsequently affects the way they behave, and the emotions they feel, in other places and with other people.”
For clarification, she is talking about what behavior geneticists and evolutionary psychologists have learned about how humans behave. Children can be taught not to swear at home, and sure enough they don’t; but around their friends it is a whole different matter because the home environment is not the same as the social environment. Children increasingly, and adults must even more so, alter their behaviors depending on the context or environment which they find themselves in. Every situation with regards to different groups, or in the company of different associates, requires different behavioral responses. So the simplistic assumption that one set of behaviors taught to a child is constant everywhere the child goes nullifies the research of those who rely on: ONE HOME ENVIONMENT = ONE SET OF CONSTANT BEHAVIORS.
She later explains, “Nor have researchers found any reliable differences between children who spent the daylight hours of their first five years in a daycare center and those who spent that time at home in the company of a parent. Children conceived by in vitro fertilization, despite the intense form of parenting they are likely to receive, are indistinguishable from those conceived in the far more common way: accidentally, often, in vino. In short, whenever a research method is used that controls for, or is not much affected by, the genetic differences between families, the home environment and the parents’ style of child-rearing are found to be ineffective in shaping children’s personalities.”
So all the media chatter about how to raise children is nonsense. Children from broken homes, children from lower economic status homes, children that do not learn to read as early as some others, etc.—almost all of these correlation studies have ignored the genetic component of personality traits (about 45%) and mental ability (about 80%).
Looking at our evolutionary past, it is plausible, as Harris claims, that children after the age of four were traditionally raised around other children, where they were socialized by their peers, built relationships with their peers, and developed certain levels of status by competing with their peers. These three processes are summarized as follows from a table in the book:
A table of three systems (Relationship System=Relation; Socialization System=Social; Status System=Status):
How data are processed:
Level of consciousness :
Developmental timetable :
Harris touches slightly on the subject of implicit versus explicit racism (without using those terms). Humans begin from an early age to categorize outsiders by attributing to them rather fixed attributes. This is the classic in-group/out-group system of differentiation. However, the relationship system overrides this system when people actually know each other as individuals. This is why we can have extremely negative attitudes about other races (implicit racism), while setting aside those attitudes when dealing with different races as individuals (the absence of explicit racism).
My primary criticism of Harris’ latest book is that she focuses on personality traits and development while sidestepping the issue of intelligence. The NEAP study also downplayed the heritability of intelligence by using “educational achievement” instead of “intelligence” (which they could have easily obtained for the children studied—no doubt because it is such an explosive subject.
I think Harris also downplays the political implications of her work. ** If races exhibit variation in personality traits and intelligence, and if this variation is substantially genetic, then immigration, or even differential emigration, can alter the character of a nation. For example, if only extroverted Finnish emigrate, the Finnish left behind would become even more introverted. Likewise, large numbers of low IQ immigrants from Mexico will reduce the United States’ average intelligence—among other changes.
* “Teens Driven to Distraction” from the Chicago Tribune, March, 24, 2006.
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