Tuesday, April 17, 2007

Sex-based variance in psychological properties and genetics

I found Pas de Deux of Sexuality Is Written in the Genes, surprisingly canny and well-written. While the unexpurgated view of sex-based differences in the brain was refreshing, I was caught totally off-guard by the argument made in the last few paragraphs:

"Several profound consequences follow from the fact that men have only one copy of the many X-related brain genes and women two. One is that many neurological diseases are more common in men because women are unlikely to suffer mutations in both copies of a gene.

Another is that men, as a group, “will have more variable brain phenotypes,” Dr. Arnold writes, because women’s second copy of every gene dampens the effects of mutations that arise in the other.

Greater male variance means that although average IQ is identical in men and women, there are fewer average men and more at both extremes."

Comments like these got Lawrence Summers in a pot full of boiling water. Can the New York Times get away with publishing such politically incorrect ideas? Perhaps more importantly, are they true? I'm neither a geneticist nor a developmental biologist, but from a statistical point of view, the idea doesn't seem flawed.

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