Christmas Books: 1
It occurred to me that some readers of this blog might be interested in hearing about them.
The Nurture Assumption by Judith Harris:
The author argues that while children are shaped by both genetics and environment, the relevant environment for most of them is not the home but the peer group. By her account, none of the popular stories about birth order, child rearing practices, and the like as determinants of adult personality are supported by the evidence. Human beings are good at recognizing that different rules apply in different environments. The typical child can and does show one face to his parents, a different one to his peers–and it is the peer group version that grows into the adult personality.
If she is right–and I think it likely that she is–that raises an interesting question about the history of psychology. How could beliefs about things such as the influence of birth order and childrearing be widely held within a scientific community when there was no evidence they were true?
Part of the answer is the confusion between genetic and environmental causation. Someone confident that personality depends only on environment will interpret similarities between parent and child as due to the affect of the environment provided by the parent. To distinguish between the two alternatives you need to look at children reared by people other than their biological parents. When you do so, it turns out that the observed similarities are in large part due to genetics.
Another part of the answer has to do with the nature of statistical evidence. Suppose you believe that birth order affects personality. You get personality evidence on a bunch of people, test for correlations between personality and birth order, and find one. First born daughters are (say) more self-confident than second and third born. You come up with a plausible explanation–the eldest child has had the experience of bossing her younger siblings around–and publish. The correlation is confirmed at the .05 level, meaning that there is no more than one chance in twenty that it could be due to chance.
Another believer in the importance of birth order does a similar study. He finds no effect for first born daughters, but discovers that last born sons are more optimistic than first born. He too comes up with a plausible explanation and publishes.
The process continues for many years. Occasionally someone is unable to find a correlation–and, since failure is rarely interesting, abandons that project in favor of something more likely to get published. Looking at the literature, it is obvious that birth order affects personality–practically everyone agrees about that–even if the details are a matter of dispute.
Only when it occurs to someone to combine the results from many studies does it become clear what is happening. With considerably more than twenty possible relations between birth order and personality, pure chance will usually result in a significant correlation for one of them–a different one each time. Pool the data and the result vanishes.
The origin of Harris's book makes an interesting story. It started as an article published in The Psychological Review. The article provoked a lot of mail–partly about the controversial argument, partly asking who the author was, since nobody in the field had ever heard of her.
Judith Harris had gotten a masters in psychology from Harvard and been discouraged from going further by a professor who assured her that she did not have the makings of a successful scholar. She left academia, married, and helped support her family by coauthoring child development textbooks. Eventually she concluded that a good deal of what those textbooks said was not supported by the evidence. The result was the article–which received the journal's prize for the year's best.
The prize is named after the Harvard professor who told her that she had no future as an academic. God, Judith Harris concluded, has a sense of humor.