Some differences between men and women are pretty apparent, others are more cryptic, and still others—which scientists have searching for—are non-existent. Like our brains.
The vast majority of people’s brains have no overall gender, according to a massive new study of MRIs of the brains of 1,400 people. Different regions may exhibit characteristics specific to different sexes, but “human brains cannot be categorized into two distinct classes,” the authors write. In fact, our brains tend to be a mosaic of both male and female qualities, regardless of gender.
The team, led by Daphna Joel, a neuroscientist at Tel Aviv University, pooled data from a number of different studies and focused on 10 different regions that typically show the largest difference between genders. Here’s Kate Wheeling, reporting for Science:
Using existing sets of MRI brain images, they measured the volume of gray matter (the dark, knobby tissue that contains the core of nerve cells) and white matter (the bundles of nerve fibers that transmit signals around the nervous system) in the brains of more than 1400 individuals. They also studied data from diffusion tensor imaging, which shows how tracts of white matter extend throughout the brain, connecting different regions.
Just 6% of the brains they studied showed characteristics that were consistently male or female, while 52% showed “substantial variability.” In fact, the researchers had to create a “maleness/femaleness” continuum to describe the entirety of their findings. Neurodiversity, it seems, is the rule rather than the exception.