To The Nurture Assumption home page
Judith Rich Harris responds
This is an excerpt from a talk given at
the Brookings Institution, Washington, DC, September 28, 2000.
Click here to read the entire talk.
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Let's look first at some of the research that has been used by developmentalists to convince journalists or other psychologists that I don't know what I'm talking about and that I have ignored studies that don't fit my thesis. Here's what Newsweek magazine labeled "Exhibit A" in its short list of studies I've supposedly ignored: Exhibit A: the work of Harvard's [Jerome] Kagan. He has shown how different parenting styles can shape a timid, shy child who perceives the world as a threat. Kagan measured babies at 4 months and at school age. The fearful children whose parents (over)protected them were still timid. Those whose parents pushed them to try new things -- "get into that sandbox and play with the other kids, dammit!" -- lost their shyness. A genetic legacy of timidity was shaped by parental behavior, says Kagan, "and these kids became far less fearful." (Begley, 1998, p. 56) The problem is that the research described here, if it exists, has never been published. The only support I've been able to find for the statement that Newsweek attributed to Kagan is one unpublished doctoral dissertation that followed 24 babies to the age of 21 months, plus one other study that followed children to the age of 3. Nothing that followed children to school age, as Newsweek claimed, or even to sandbox age. The doctoral dissertation is by Doreen Arcus, one of Kagan's students. It's still unpublished, nearly ten years after it was handed in, but it's often cited (as Arcus, 1991, or as Arcus, Gardner, & Anderson, 1992). As far as I've been able to determine, it's the only evidence Kagan and his students have managed to produce, in more than 20 years of studying fearful children, to support their belief in parental influences on fearfulness. Arcus found a positive correlation between overprotective parenting in infancy and fearfulness at age 21 months. The correlation at age 3 was found, for boys only, by another group of researchers, Park, Belsky, Putnam, and Crnic (1997). Assuming that this finding can be extended to older children of both sexes, what would it prove? Only that anxious, fearful parents tend to produce anxious, fearful offspring. Such traits are heritable -- Kagan himself (1994, p. 168) reported estimates of .50 to .70 for the heritability of fearfulness -- and therefore children born with a predisposition to be anxious or fearful are more likely to be reared by anxious, fearful parents (and vice versa). We can get a more accurate estimate of environmental influences on this personality trait by looking at adopted children. Adoption studies provide no support for the belief that the parents' child-rearing style has an influence on the adoptee's adult personality (Plomin, DeFries, McClearn, & Rutter, 1997). |