Male and Female Brains Wired Differently

The brains of men contain stronger front-to-rear connections while those of women are better connected from left to right.

Dec 4, 2013
Bob Grant

WIKIMEDIA, MINIME 12358Update (January 16, 2015): See “Crossed Wires” for an extended discussion of this study and the published results.

New research on the neural connections within the human brain suggests sex-based differences that many have suspected for centuries: women seem to be wired more for socialization and memory while men appear geared toward perception and coordinated action. The female brain appears to have increased connection between neurons in the right and left hemispheres of the brain, and males seem to have increased neural communication within hemispheres from frontal to rear portions of the organ. University of Pennsylvania researchers announced the results, generated by scanning the brains of about 1,000 people using a technique called diffusion tensor imaging, on Monday (December 2) in the PNAS.

UPenn Perelman School of Medicine radiologist Ragini Verma and colleagues scanned the brains of more than 400 males and more than 500 females from 8 to 22 years old and found distinct differences in the brains of male versus female subjects older than age 13. The cortices in female brains were more connected between right and left hemispheres, an arrangement that facilitates emotional processing and the ability to infer others’ intentions in social interactions. In male brains, however, the cortex was more connected to rear brain regions, such as the cerebellum, which suggests greater synergy between perception and action.

“There is biology to some of the behavior we see among men and women,” Verma told the Los Angeles Times. “In the population, men have stronger front-back connectivity, and women have inter-hemispheric or left-right connectivity more than the men. It’s not that one or the other gender lacks the connectivity altogether, it’s just that one is stronger than the other.”

These physiological differences, which didn’t appear in stark contrast in those under 14, could possibly give rise to behavioral differences between the sexes. “So, if there was a task that involved logical and intuitive thinking, the study says that women are predisposed, or have stronger connectivity as a population, so they should be better at it,” Verma told the LA Times. “For men, it says they are very heavily connected in the cerebellum, which is an area that controls the motor skills. And they are connected front to back. The back side of the brain is the area by which you perceive things, and the front part of the brain interprets it and makes you perform an action. So if you had a task like skiing or learning a new sport, if you had stronger front-back connectivity and a very strong cerebellum connectivity, you would be better at it.”

Studying the structural and function differences between male and female brains could help ferret out causes and possible treatments for certain brain disorders, the authors suggested. “It’s quite striking how complementary the brains of women and men really are," Ruben Gur, a co-author on the study, said in a statement. “Detailed connectome maps of the brain will not only help us better understand the differences between how men and women think, but it will also give us more insight into the roots of neurological disorders, which are often sex-related.”

But at least one researcher is questioning the argument that Verma and her team are making for the neural connectivity differences they found being a function of sex. “One important possibility the authors don’t consider is that their results have more to do with brain size than brain sex,” wrote University of Melbourne social and developmental psychologist Cordelia Fine in a blog post published by The Conversation. “Male brains are, on average, larger than females and a large brain is not simply a smaller brain scaled up.”

Fine, who wrote 2011’s Delusions of Gender, a book that seeks to counter propositions that sex-based differences are biologically hardwired, explained that larger brains must be organized differently to deal with increased energy demands, decrease communication times, and minimize wiring costs. She cited an earlier study published by the same group at UPenn, also published in PNAS, which reported differences between how males and females performed on a spate of psychological tests.

“Rather than drawing on their impressively rich dataset to empirically test questions about how brain connectivity characteristics relate to behavior, the authors instead offer untested stereotype-based speculation,” wrote Fine. “These characteristics of the [current] PNAS study are very common in neuroscientific investigations of male/female sex differences, and represent two important ways in which scientific research can be subtly ‘neurosexist,’ reinforcing and legitimating gender stereotypes in ways that are not scientifically justified.”