When It Comes to Brains, Size Matters

June 20, 2008

Findings of a three-year study by researchers at the University of California, Riverside and the University of Florida, Gainesville run counter to the popular belief that women have better language skills than men.

In a study of 200 university students, the researchers found that women and men performed similarly on tests of language and reading skills. Differences in brain organization between men and women may be driven by sex differences in brain size, they said.

“People have said women have relatively larger language areas of the brain,” said Christine Chiarello, UCR professor of psychology. “In none of our language tasks were women better than men. When you account for differences in brain size between men and women there are few differences in the relative size of areas. While there are differences between men and women, those differences are minimal compared to the wide range of individual differences in both sexes.”

The study, “Size Matters: Cerebral Volume Influences Sex Differences in Neuroanatomy,” was published recently in the journal Cerebral Cortex.

The researchers gathered demographic data, tested language and reading skills, and performed magnetic resonance imaging to map brain structures of 100 female students and 100 male students. The men and women were similar in age, parental education and proportion of students who were right- or left-handed.

There were great individual differences in brain organization, brain size and where language and speech are processed, Chiarello said. For most people, speech and language are processed in the left half of the brain.

Differences in brain size account for much of the variance in brain structure size that at first glance might appear to be attributable to sex, Chiarello said. On average, the brains of men in the study were 13 percent larger than the women.

Men and women “confront similar cognitive challenges using differently sized neural machinery,” the researchers wrote. Their findings imply that “any sex-specific adaptations to overall brain size are not associated with large relative differences in the size of various cerebral regions. In this respect, our results suggest that brain size matters more than sex.”

Study co-authors include Chiarello; Christiana M. Leonard and Stephen Towler of the Evelyn F. and William L. McKnight Brain Institute of the University of Florida; UCR graduate students Suzanne Welcome and Laura K. Halderman; Ron Otto of the Computerized Diagnostic Imaging Center, Riverside; and Mark A. Eckert of the Medical University of North Carolina.

Source: University of Florida

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4.2 / 5 (6) Jun 20, 2008
"..brain size matters more than sex."

But will never be quite as appealing.
5 / 5 (2) Jun 20, 2008
Autism disproportionately affects males (4:1), and it is associated with excessive brain growth in infancy and a larger than average brain size. Thus, on the contrary is seems that overall brain size is sex specific, and those with larger than average brains are more likely to have autism and autistic traits.

Evidence of Brain Overgrowth in the First Year of Life in Autism. E Courchesne, R Carper, N Akshoomoff - JAMA, 2003
4 / 5 (1) Jun 20, 2008
I'm confused...
"On average, the brains of men in the study were 13 percent larger than the women."
...but in the test men and women performed closely? So brain size really doesn't matter?

Plus the test was done on college students, most likely from the same college, which means they are all roughly of the same intelligence anyway.
4 / 5 (1) Jun 20, 2008
I think what they mean is that their is little or no difference between men and women in the absolute size of the parts of their brains that are used for language.

They are discounting earlier studies that said that women have larger proportions of their brains set aside for language skills than men,
and so are better than men at language skills.

They claim that the differences that are observed between the sexes (in the proportion or pecentage of brain tissue set aside for language skills) are not significant because the larger size of the average male brain means that there is little difference between the sexes in the absolute size of these areas of the brain.

e.g. The average male brain could appear to have a lower percentage of its brain tissue set aside for language skills than the average female brain yet the male brain could still dedicate the same absolute amount of brain tissue to language skills as the female brain because of the male brain's overall larger size.
3 / 5 (1) Jun 21, 2008
Doesn't anyone think it is queer that there is no mention of relative body mass which is what is commonly considered the factor that accounts for brain mass differences? Also the reporter uses the word "size" to refer to differences. This is another odd thing.
2.5 / 5 (2) Jun 21, 2008
Brain size relative to body mass is a rough measure of evolutionary pressures that favor energy being devoted to processing tasks, since a larger brain tends to use more energy.. and energy efficiency is a strong counter pressure. While the brain is growing (and using more energy), it is likely that other positive processing adaptations within the brain are being selected.. which muddies the issue somewhat. Within a species where ancestors on the whole had pressures that are common, I'm not it would be relevant in the way you expect.

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