Thursday, May 26, 2005

Do bigger brains = higher intelligence?

I have always found the research relating brain size/volume to intelligence of interest---more as a piece of "cocktail trivia" general knowledge. I've never bothered to read/study the "why" behind this line of research, and the current article cited below does not either. This brief aricle simply presents a meta-analysis estimate of the population correlation between brain volume and intelligence.

The correlation reported is .33. Of course, in practical terms this means that measures of intelligence and brain volume share approximately 10% common variance. A significant finding....but, not much in the way of practical implications (IMHO). I would not suggest that applied assessment professionals start carrying tape measures in their test kids.

Just FYI "interesting" information.

McDaniel, M. A. (2005). Big-brained people are smarter: A meta-analysis of the relationship between in vivo brain volume and intelligence. Intelligence, In Press, Corrected Proof.

  • The relationship between brain volume and intelligence has been a topic of a scientific debate since at least the 1830s. To address the debate, a meta-analysis of the relationship between in vivo brain volume and intelligence was conducted. Based on 37 samples across 1530 people, the population correlation was estimated at 0.33. The correlation is higher for females than males. It is also higher for adults than children. For all age and sex groups, it is clear that brain volume is positively correlated with intelligence.

If anyone wants to research this literature in greater depth (big and small brain-headed scholars are all welcome - this is an equal brain-size opportunity blog), below are a few references I found in the IAP Reference DataBase
  • Colom, R., LluisFont, J. M., & AndresPueyo, A. (2005). The generational intelligence gains are caused by decreasing variance in the lower half of the distribution: Supporting evidence for the nutrition hypothesis. Intelligence, 33(1), 83-91.
  • Haier, R. J., Chueh, D., Touchette, P., Lott, I. et al. (1995). Brain size and cerebral glucose metabolic rate in nonspecific mental retardation and Down syndrome. Intelligence, 20(2), 191-210.
  • Lynn, R., Allik, J., & Must, O. (2000). Sex differences in brain size, stature and intelligence in children and adolescents: some evidence from Estonia. Personality and Individual Differences, 29(3), 555-560.
  • Rushton, J. P. (2004). Placing intelligence into an evolutionary framework or how g fits into the r-K matrix of life-history traits including longevity. Intelligence, 32(4), 321-328.
  • Rushton, J. P. (1991). "Mongoloid^Caucasoid differences in brain size from military sample": Reply. Intelligence, 15(3), 365-367.
  • Rushton, J. P. (1991). Mongoloid^Caucasoid differences in brain size from military samples. Intelligence, 15(3), 351-359.
  • Rushton, J. P. (1997). Cranial size and IQ in Asian Americans from birth to age seven. Intelligence, 25(1), 7-20.
  • Wickett, J. C., Vernon, P. A., & Lee, D. H. (2000). Relationships between factors of intelligence and brain volume. Personality and Individual Differences, 29(6), 1095-1122.
  • Willerman, L. (1991). "Mongoloid-Caucasoid differences in brain size from military samples": Commentary. Intelligence, 15(3), 361-364.
  • Willerman, L., Schultz, R., Rutledge, J. N., & Bigler, E. D. (1991). In vivo brain size and intelligence. Intelligence, 15(2), 223-228.

1 comment:

Anonymous said...

This is a questionable result. There are plenty of studies that show that when corrected for other physiological characteristics, the relationship doesn't exist.

Phrenology died a slow death, let's not perpetuate similar myths.