Ideas that one sex has an inherent genetic advantage over the other have long been held as taboo, lest low-level biological variance be unfairly and unscientifically used to prop up gender stereotypes. But new research finds that baseline genetic differences in the brain do affect a person's psychological worldview—creating specific real-world advantages and disadvantages for each gender.
"There is plenty of evidence from many years of work in psychology and neuroscience that females are more socially adept and they have better verbal skills compared to males,” says Dr. Bernard Crespi, a professor of evolutionary biology at Simon Fraser University. He says women are better at managing complex social relationships and men are better at favoring structure and order. Crespi and his collaborator Christopher Badcock, a professor of sociology at London School of Economics, think there might be a link between a normal female predisposition towards empathy and sociality—as an expression of gender-based genetics—and psychosis, as an extreme expression of those genes. After all, what is paranoia, says Crespi, if not "putting yourself in someone else's place, or thinking you know what they're thinking" taken to a dysfunctional level?
Their research suggests that not only are male and female brains different, but that they exist on a spectrum with autism and psychosis at either end. “The female brain is a little bit partway toward psychosis and depression and the male brain already naturally partway toward a sort of autistic cognition,” says Crespi.
The story of the “extreme-female brain” begins in Austria in the 1940s. There, the pediatrician Hans Asperger was studying a set of patients with what would come to be called Autism Spectrum Disorder. "His name has become associated with so-called high-functioning Autism, or Asperger’s syndrome, partly by historical accident but partly because a lot of his cases were in fact quite high-functioning," says Badcock. In his research, Asperger noted his patients, with their intense focus on order and on the world of things, "looked to him almost like a caricature of normal male mentality," Badcock says. "So the idea that autism might represent an extreme-male brain really began with Asperger, and then it kind of got forgotten about," he adds.
In the 1990s, further research showed the majority of autistics, especially high-functioning autistics, turn out to be men. “With Asperger’s syndrome, males outnumber females—some people say 15-to-1, but definitely ten-to-one," Badcock says. At Cambridge University, the researcher Simon Baron-Cohen developed the idea originally brought up by Asperger that autism was an "extreme-male brain," which he wrote about in his book "The Essential Difference" and elsewhere. Baron-Cohen's work sought to find the neurobiological origin for autism, a disorder that now affects one in ninety-one U.S. children, and one in fifty-eight boys.
Jumping off from Baron-Cohen's work, Badcock hypothesized that male and female brains exist on a spectrum, at the ends of which are opposing mental disorders: if paranoia is the opposite of autism—and if autism can be seen as a kind of extreme-male brain—then paranoia might be a kind of extreme-female brain. And this all might be a direct result of a person's sex chromosomes, which determine whether a child will be a male or female, he and Crespi theorized. Humans have 23 pairs of chromosomes in their DNA, one of which consists of the sex chromosomes—two X-chromosomes for women and an X- and Y-chromosome for men. According to Badcock's theory, "If the father's genes [Y-chromosome] are over-expressed and/or the mother's X-chromosome genes are under-expressed, a person is prone to autism." Likewise if the X-chromosome genes are over-expressed and/or the father's genes under-expressed, that person is more likely to suffer from paranoia and psychosis.
To test this theory, Crespi looked at rare cases in which more X-chromosomes are present than should be, such as Klinefelter’s Syndrome (XXY) and Super Female Syndrome (XXX), as well as cases like Turner Syndrome, in which one of a girl's X-chromosomes is missing. They hypothesized that the presence of more or fewer X-chromosomes is an exaggerated model for the more or less imprinting of XX or XY genes. Crespi and Badcock expected a correlation with the genetic make up and mental disorders, and that is exactly what they found. "If you have extra X chromosome genes you are more likely to suffer from psychosis, but if you’ve got fewer X chromosome genes, as in Turner Syndrome, you are more likely to be diagnosed autistic,” says Badcock.
Badcock admits this theory is controversial. Yet he says there is already compelling evidence to bolster its claims. The problem is the evidence is technical and obscure; for instance, “not a lot of people know that every single case of Prader-Willi syndrome in which the child has inherited two copies of the mother’s chromosome 15…gets diagnosed psychotic when they grow up.” This case of over-expression of the mother's gene, says Badcock, is the strongest link between genetics and psychiatry known to science.
So what does all this mean? Differences between male and female brains, and between the X- and Y-chromosomes that build our neural architecture, are a shifting cloud of statistical averages stretched along our evolution. Individual traits are not fixed in gender-wide neuro-determinants for our behavior. Moreover, in the past pseudoscience has been used to buttress stereotypes. The question becomes can differences between the female and male brain, such as a predisposition toward sociality in the former, be empowering? Cordelia Fine, academic psychologist and author of “Delusions of Gender: How Our Minds, Society, and Neurosexism Create Difference,” doesn’t think so.
"Women should think twice before falling for this spin," says Fine. "First, it lacks solid scientific support. There are remarkably few well-established sex differences in the brain, and none that have been scientifically related to empathizing or 'systemizing' abilities. It’s also questionable whether the sexes even reliably differ in these skills," she says. "Second, underneath the veneer of 'empowerment' promised by the notion of a ‘female brain’ with its own special talents are the old thinkers versus feelers stereotypes: men are built to advance civilization, while women are built to nurture it."
—Crespi, B. and Badcock, C. "Psychosis and autism as diametrical disorders of the social brain."
—Badcock, C. and Crespi, B. "Battle of the sexes may set the brain."