Monday, December 26, 2011

Study: Sex differences in brain volume are related to specific skills, not to general intelligence

A new study in the journal Intelligence of 100 Spaniard male and female college students reports that men, on average, have more total brain volume (TBV) and more gray matter volume (GMV), but these do not translate into higher general intelligence (g). Sex differences only appear for specific mental abilities. TBV and GMV are positively correlated with greater visuospatial skills (i.e., mental rotation). By contrast, higher specific verbal skills are associated with lower: 1) visuospatial skills, 2) total brain volume, and 3) white matter volume. From these results, the researchers conclude that larger male brains provide more total neurons needed for mental manipulation of 3D objects, while smaller female brains might work more efficiently to give enhanced verbal skills (that are unrelated to g).


bgc said...

The researchers have almost certainly made a mistake - I can't get at the whole paper at present, however.

My guess is that the sample is probably range restricted with IQ - most colleges sample a narrow stratum of IQ, so if you compare male and female students from the same college you are controlling-away nearly all the IQ variation in the general population.

Anonymous said...

Quoting the researcher's conclusions:

"while smaller ______ brains might work more efficiently to give enhanced verbal skills (that are unrelated to g)."

I wish more people realized that silver tongues dont necessarily equate with problem-solving abilities or ethics.

Anonymous said...

Very good point bgc and that's a flaw that is extremely widespread in psychological research.

Anonymous said...

This is consistent with previous studies on this topic.

For instance..

"Ability correlated with cerebral volume, but the relationship depended on the realm of intelligence studied, as well as the sex and hemispheric functional lateralization of the subject. General verbal ability was positively correlated with cerebral volume and each hemisphere's volume in women and in right-handed men accounting for 36% of the variation in verbal intelligence. There was no evidence of such a relationship in non-right-handed men, indicating that at least for verbal intelligence, functional asymmetry may be a relevant factor in structure–function relationships in men, but not in women. In women, general visuospatial ability was also positively correlated with cerebral volume, but less strongly, accounting for ∼10% of the variance. In men, there was a non-significant trend of a negative correlation between visuospatial ability and cerebral volume, suggesting that the neural substrate of visuospatial ability may differ between the sexes."