Foxp2: the 'language protein' that differs in male and female brains

The study

On February 20, 2013, The Journal of Neuroscience published a study by J. Michael Bowers, Margaret McCarthy, and colleagues at the University of Maryland School of Medicine on Foxp2 — a protein long linked to speech and language development in humans and vocal communication in birds and other mammals. The question: does its expression in the developing brain differ between the sexes?

The team examined four-day-old male and female rat pups, measuring Foxp2 protein in brain regions tied to cognition, emotion, and vocalization, and recording the pups' ultrasonic distress calls during five minutes of separation from their mothers. The males had more Foxp2 protein than the females in nearly every brain region examined — and they were far chattier, producing nearly double the total vocalizations. Mothers preferentially retrieved the noisier males first.

Then came the decisive experiment: when the researchers lowered Foxp2 in the males and raised it in the females, the sex difference in calling reversed — males sounded like females and vice versa, and the mothers flipped their retrieval preference accordingly.

The human part — and its limits

The team also analyzed Foxp2 in a small group of human children, aged four to five, whose brains were examined post-mortem. Here the direction flipped: the girls had about 30 percent more Foxp2 protein than the boys. The authors suggested this might relate to a well-documented developmental pattern — on average, girls tend to speak earlier and with greater complexity than boys of the same age.

Note the cautions: the human sample was tiny, the subjects were young children (not chatty adults), and in the animal experiment, the more vocal sex was the one with more Foxp2 — which sits awkwardly with any simple "more protein = more talking" story for grown women and men.

What the headlines got wrong

Much of the 2013 coverage framed the study as a biological explanation for why women supposedly talk more than men — often alongside the claim that women speak 20,000 words a day to men's 7,000. That word-count figure is a long-debunked myth (real research, notably Mehl et al., 2007, found no meaningful sex difference in daily word output), and the study itself said nothing about adult talkativeness. What it actually showed was subtler and more interesting: a molecular lever that, at least in developing brains, tunes how much the young of each sex vocalize — in opposite directions in rats and humans.

Archive summary, February 2013. The Society for Neuroscience's original release: Language protein differs in males, females.