Friday, December 23, 2005

Bigger is better   posted by Theresa @ 12/23/2005 08:19:00 AM

Sandra Witelson (who examined Albert Einstein's brain), et al., have a paper in Brain which reports on their study on intelligence and brain size in 100 postmortem brains. They conclude that bigger is indeed better; however, they found differences between men and women.

From EurekaAlert:
In women, verbal intelligence was clearly correlated with brain size, accounting for 36 percent of the verbal IQ score. In men, this was true for right-handers only, indicating that brain asymmetry is a factor in men.

Spatial intelligence was also correlated with brain size in women, but less strongly. In men, spatial ability was not related to overall brain size. These results suggest that women may use verbal strategies in spatial thinking, but that in men, verbal and spatial thinking are more distinct....

Furthermore, from the journal abstract:
We report the results of such a study on 100 cases (58 women and 42 men) having prospectively obtained Full Scale Wechsler Adult Intelligence Scale scores. 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. Analyses of additional research subjects used as test cases provided support for our regression models. In men, visuospatial ability and cerebral volume were strongly linked via the factor of chronological age, suggesting that the well-documented decline in visuospatial intelligence with age is related, at least in right-handed men, to the decrease in cerebral volume with age. We found that cerebral volume decreased only minimally with age in women. This leaves unknown the neural substrate underlying the visuospatial decline with age in women. Body height was found to account for 1-4% of the variation in cerebral volume within each sex, leaving the basis of the well-documented sex difference in cerebral volume unaccounted for.

Hat tip to Fly.