Autism is about four times more common in boys than in girls, according to the CDC. But the reason for this trend still isn’t completely clear. One hypothesis, proposed by scientist Simon Baron-Cohen, is the extreme male brain theory, which states that men’s general propensity for systematizing and women’s generally propensity for empathizing render autism an extreme form of the male brain.
But the theory has been critiqued, as others believe that that biological difference cannot account for such a large discrepancy, and that genetics, social learning, and diagnostic bias play a role as well.