Do you think you have a female brain? A male brain?
According to a new study, there’s no such thing as a distinctly female or male brain. Though the two seem to be built very differently, that’s not the case.
An analysis of more than 100 studies found that the volume of a man’s brain is 8 to 13 percent greater than that of a woman’s brain on average, The Los Angeles Times reports. Some of the largest differences were in the parts of the brain that control emotion, memory, language and behavior, according to a 2014 report in the journal Neuroscience and Biobehavioral Reviews.
To discover whether the structural differences bled over into cognitive differences, scientists looked at detailed brain scans of men and women.
An analysis of more than 1,400 MRI scans found that biologically unmistakable sex differences do not sit in the brain. Instead, researchers discovered the brain holds a combination of feminine and masculine characteristics, Philly.com reported.
“This is the first study to look at the brain as a whole and ask whether brains are of two types. The answer is no,” lead author Daphna Joel, a psychologist and professor at Tel-Aviv University in Israel, said. “Each person possesses a unique mosaic of characteristics: some more common in females compared to males, some more common in males compared to females, and some common in both.”
Additionally, the team wrote, in a study published Monday in the Proceedings of the National Academy of Sciences, that “although there are sex/gender differences in brain structure, brains do not fall into two classes, one typical of males and the other typical of females.”
“Each brain is a unique mosaic of features, some of which may be more common in males compared with females, and still others may be common in both females and males.”
The researchers continued by examining examples of brain “elements” that were either clearly female or male. Or, they searched for examples of measurements that seemed to cluster one way for women and one for men without much overlap. Then, the researchers looked to see whether women had “female” versions and men had “male” versions.
They looked at 112 men and 169 women ages 18 to 79 with sets of MRIs that measured the volume of gray matter in their brains. And on those scans, they looked at 116 regions and focused on the 10 that showed the largest difference between men and women, LA Times reports.
Only 6 percent of the brains ranked “most male” or “most female” in all 10 categories. But the researchers also found that 35 percent showed “substantial variability.”
The analysis was then repeated with different barriers for “most female” and “most male.” And the mixture of male and female characteristics greatly outnumbered the brains that were mostly “male” and mostly “female.”
Afterward, the researchers retraced their steps with other brain scans that measured thickness of gray matter in different areas of the brain. They got the same results.
When scientists looked at the brains of American teens, they discovered only 1.8 percent of them had consistently male or female compared with 59 percent who showed “substantial variability,” based on 570 participants in the Maryland Adolescent Development in Context Study.
“This extensive overlap undermines any attempt to distinguish between a ‘male’ and a ‘female’ form for specific brain features,” Joel said. Joel and her colleagues added that their conclusions have “important implications for social debates on long-standing issues such as the desirability of single-sex education an the meaning of sex/gender as a social category.”