A recent study of more than 46,000 scans concluded that there are "significant gender differences" in the brains of men and women. The authors believe that further examination of the results might help scientists understand and treat psychiatric disorders better in the future.
The researchers used single photon emission computed tomography (SPECT)—a type of imaging that, unlike an x-ray, actually shows blood flow to tissue and different organs—to analyze the brains of participants. Whereas previous studies had noted differences in the brains of men and women, this is the largest-scale study on the topic conducted so far.
The big news from the study was that women had higher brain activity in general. Women's brains also had more blood flow to the prefrontal cortex, which facilitates focus, impulse control, and decision making.
The results led to spectacular claims from one of the study's authors.
The lead author of the study, Daniel Amen, MD, claims that because of this increased brain activity, women have greater strengths in many areas. He lists empathy, intuition, collaboration, self-control, and appropriate worry as areas where women's brains are superior to men's.
"Females are neurologically well-equipped to lead, manage and help us resolve the major problems of the world," Amen wrote.
"Men have been in positions of power since the inception of the human race, and while the progress of civilization is impressive, we still face war, strife, power struggles, ill health and more every day."
Unsurprisingly, Amen's assertions received serious backlash from those who thought it went too far. One blogger accused Amen of trying to sell books by pandering to women. The same blogger also suggested that SPECT brain scans are unnecessary and expose patients to dangerous gamma rays.
Whether you believe Amen's conclusions are sound or not, there is solid proof that the brains of men and women have differences.
An analysis of the brains of 5,216 participants from the United Kingdom confirmed that there are noticeable differences in the brains of men and women. For instance, men have a higher total brain volume than women (though to be clear, that doesn't necessarily equate to higher intelligence).
The study showed that while men had larger brains on average, they also had much more variation in brain size than women. The researchers surmise that this could be due to something they call a "female-protective" mechanism. While the phenomenon is not entirely understood, a women's two X chromosomes can protect her from certain mutations that men are susceptible to. This leads to less physical variation in females in general, including brain size.
Understanding the differences could help treat mental disorders.
Other differences include that men's brains had a higher cortical volume on average, while women had thicker cortices. These differences may not mean much to laypeople, but in the right hands, the data could help psychiatrists treat mental disorders, which affect men and women differently and are known to be associated with these brain structures.
For instance, women are almost twice as likely to develop Alzheimer's disease as men are. "There are enough biological questions pointing to increased risk in women that we need to delve into that and find out why," says Maria Carrillo, chief science officer of the Alzheimer's Association. "There is a lot that is not understood and not known. It’s time we did something about it."