Gender differences in brain connectivity (if any) aren't hard-wired

A headline story this morning, featured in several news outlets, reported on a new study published online in PNAS yesterday that allegedly confirms that there are major brain differences between men and women. In the study Ragini Verma, an associate professor in the Department of Radiology at the University of Pennsylvania, and colleagues examined the neural connectivity across the whole brain in 949 individuals (521 females and 428 males) aged 8 to 22 years using diffuse tensor imaging (DTI).

The researchers found that in certain age groups, females had greater inter-hemispheric connectivity in the supratentorial region (the part of the brain above the cerebellum), whereas males exhibited greater intra-hemispheric connectivity as well as greater interhemispheric connectivity in the cerebellum. The cerebellum has been implicated in certain forms of knowledge of action and knowledge-how, interhemispheric connectivity seems crucial for many social skills, and intrahemispheric connectivity in local sensory regions may lead to richer perceptual experiences. So, on the basis of these findings, many news reports concluded that men have a greater perception to action potential, whereas women have a greater potential for communicating and connecting “the analytical and intuition.” Some concluded that gender differences in brain connectivity are hard-wired.

These reports, however, are for the most part based on a misreading of the article. It’s important to emphasize, as the authors do, that the study revealed very few gender differences in connectivity in children younger than 13 years of age. The differences in connectivity were mainly attributable to individuals between 14 and 22.

Furthermore, the authors report that the behavioral study they conducted confirmed pronounced sex differences in the sample but primarily in individuals between 12 and 14 years of age. Female participants in this age group scored higher on attention, word and face memory tests as well as social cognition tests, whereas male participants performed better on spatial processing and motor and sensorimotor speed. So, the observed differences in behavior were restricted to the early teen years.

The researchers, however, did not report pronounced differences in performance in older teens or young adults. Nor did they show that the changes in connectivity in the 14-22 age group will last beyond the twentysecond year. What the results do show is that gender differences aren't very significant until the early teen years. These are the years during which the brain undergoes massive pruning, and the activities children engage in at least partially modulate this pruning of neural connections. So, the study simply doesn't reveal “strong hard-wired differences” in men and women. Quite on the contrary. The findings seem to be inconsistent with genetic determinism as well as connectome determinism and consistent with the theory that if there is a pronounced and long-lasting difference in brain connectivity between men and women, then it is plausibly fostered by our societal norms.