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April 23, 2004

Math, boys vs. girls & hemispheric integration

I was recently directed to this short article titled "Math favors boys over girls." Rather ho-hum, and if you are want a quick primer that explains the differential by emphasizing the greater variance of male IQ, here you go [1].

But I did track down the original paper (full text PDF at the link) that the piece above was based on, "Interhemispheric Interaction During Global–Local Processing in Mathematically Gifted Adolescents, Average-Ability Youth, and College Student." It was interesting to me that the focus of the paper did not seem to be gender differences, but rather, the importance of an fully integrated and active right hemisphere during mental tasks, especially among the mathematically gifted. Additionally, the researchers note the over-representation of left-handedness among the mathematically gifted (the right brain controls the left half of the body). The article above was in The Times of India, and knowing how negatively South Asians tend to view those of the leftish persuasion, I am not surprised they did not play up that angle.

On a related note, a month ago Diana asked me about the EP reasoning behind the persistence of right-handed dominance. She did not find this article that hypothesized a correlation between right-handedness and left-brained speech ability, a heterozygote advantage that resulted in balancing selection, ergo residual frequency of non-hand-biased homozygotes (some of whom are "left handed"), convincing. But if we want to go out on a limb, what the paper above might suggest is that there is a possible avenue of selection pressure in favor of left-handedness.

It is often said that "naturally" about 10% of the population prefers the left hand to the right. I would be willing to bet that coincidentally that's probably the proportion of the population that prefers mathematical study to more verbally oriented endeavors. Perhaps the 90/10 is just an ESS?

[1] I recall seeing a study which tracked boys and girls of the same mathematical aptitudes (as measured by tests taken when they were 13), and there was still a strong tendency for the females to go into "people" fields like medicine and law over physical science & engineering graduate programs 10 years later, so the interplay of personal preference & cultural expectations amplify the differences (the two latter factors I assume are bi-directional in their influence).

Posted by razib at 02:08 AM