A new study shows that human brains do not fit neatly into 'male' and 'female' categories. Instead, most contain features from both.
Researchers at Israel's Tel Aviv University identified several structural differences between the brains of men and women, but could not tell the gender of an individual just by looking at a brain scan image.
Scientists have long held that there are differences between men's and women's brains. The Tel Aviv team wanted to find out if those differences are significant enough to create two distinctly different types of brain, just as there are distinctly male and female reproductive organs.
"To answer this question, we looked at over 1,400 brains from different samples," said Daphna Joel, who heads the psychobiology program at Tel Aviv University. "In each sample we determined the regions showing the largest differences, and then we asked whether these differences add up so whether the subject is on the female end, as you can see here on the female end of the continuum in one region, whether this subject will also be on the female end of the continuum on all other regions, and what we found is that this is very rare."
The researchers determined that specific parts of the brain do show sex differences, but an individual brain rarely has all 'male' or all 'female' traits.
So what are the social repercussions of the findings? Joel suggests that we should try to move from the language categorizing people according to their sex toward the language treating everyone according to their specific characteristics and interests.
"It means that our assumption as a society that our sex category—whether we have male or female genitalia has implications to what we would love, what we would like to do and what type of person we will be that also people come in two types, male nature and female nature—this has no scientific basis and people are very different from each other," she said.
While most scientists agree that brains contain varying mixtures of male and female anatomical traits, many say that prevailing evidence proves that sex has an important influence on brain function.
Mental health experts, for example, argue that exploring biological differences between male and female brains may help answer questions such as why men are more likely than women to develop autism, while women are more likely to suffer from depression. They say more study is needed to determine in what way and to what extent one's sex influences the brain.