New Israeli research, which for the first time studied the whole brain, rather than separate regions of it, suggests that there is no such thing as a “male brain” or a “female brain.”
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According to the study, which was published yesterday in the American Journal Proceedings of the National Academy of Sciences, one can identify features that are more common in either male brains or female brains, but that there is only one type of brain, and the brain of every individual is a unique mosaic that combines the two types of characteristics.
“We as a society reference the genitalia as a model when we think of the differences between men and women in terms of their characteristics, desires and behaviors,” explained Prof. Daphna Joel of the School of Psychology and the Sagol School of Brain Sciences at Tel Aviv University, who led the study. “But when we look at the details, we find that none of us really matches the stereotype of the group.
“In this study we sought to examine if there are two types of brains – male and female – just as there are two separate and distinct types of genitalia,” Joel continued. “There’s no doubt that there are differences between men and women, and studies have even found differences between the brains of women and the brains of men. But this doesn’t mean that any individual person has a ‘female brain’ or a ‘male brain,’ the way she or he has female or male sex organs.”
Joel’s study, conducted with researchers from the neurobiology and math departments at TAU, along with scientists from the Max Planck Institute in Leipzig and the University of Zurich, approaches the male-female brain question from several directions. On the physiological level, it is based on measuring dozens of brain regions of more than 1,400 people, and on the psychological level it analyzed the characteristics of thousands of men and women.
During the first stage, the researchers examined the MRI scans of more than 1,400 people, identifying a range of measurable characteristics, like the size of certain regions, or the strength of the neural connections between different regions, that were most different in men and women. For each of these regions or connections, they established the most common sizes/strengths in men compared to women (the “male extreme”), the sizes/strengths most common to both genders, and the sizes/strengths most common in women (the “female extreme”).
The researchers then examined each brain separately, to determine if any of them showed only characteristics matching the male extreme, characteristics matching the female extreme, or a mix. The conclusions were unequivocal: Less than 8 percent of the brains examined showed characteristics solely of one extreme.
The second part of the study examined psychological characteristics (like personality traits, attitudes, behaviors) of more than 5,500 people from three different databases. As with the MRIs, they found differences between men and women in some of the variables, but they found almost no one who had only female or male characteristics. The traits and habits examined included watching porno films or talk shows, boxing, golf, housework, depression, and many others. An in-depth analysis of them did not produce a male or female prototype, but a complex mosaic. “Few people exhibit all-female or all-male qualities. Most people have a mosaic of female and male traits,” Joel explained.
“Until now, scientists made do with saying that there are statistical differences between the two genders. We showed that the fact that there are statistical differences between the groups doesn’t mean there are two distinct types of brains,” she said.
The new study is liable to rekindle the scientific and social debates about gender identities and differences. Previous studies claimed to have found differences between male and female brains. For example, just last year the same journal published a study showing that the average woman has a preponderance of neural connections between the right and left hemispheres of their brains, while in men, the connections are stronger between the front and rear lobes of their brains, making men more hard-wired for perception and coordination, while women were hard-wired for memory and social skills.
Joel’s researchers did a similar analysis, and while they also found differences in the neural connections between men and women, there wasn’t a single person in whom the seven connections analyzed followed solely “male” or “female” patterns. In contrast, 48 percent of the brains demonstrated both male and female connection patterns.
Joel claims that the article from 2014 demonstrates the problem in her field. Although the discovery of differences doesn’t prove there are two types of brains, most researchers interpret their results that way. Joel hopes that after publication of her study, researchers will stop making such claims without checking them scientifically.
“The problem is not our gender but the significance we give it,” she said. “Now all we have to do is change the world.”