Researchers report a sex difference in the expression of a language-associated protein in rats or humans. They analyzed the levels of Foxp2 protein in the brains of four-day-old female and male rats and compared the ultrasonic distress calls made by the animals when separated from their mothers and siblings. Compared with females, males had more of the protein in brain areas associated with cognition, emotion, and vocalization. They also made more noise than females—and were preferentially retrieved and returned to the nest first by the mother. When Foxp2 protein levels were reduced in male pups and increased in female pups, they reversed the sex difference in the distress calls, causing males to sound like females and the females like males. This change led the mother to reverse her behavior as well, preferentially retrieving the females over the males. In a preliminary study of Foxp2 protein in a small group of children, researchers found that girls had more of the Foxp2 protein in the cortex, a brain region associated with language, than age-matched boys (opposite from rat brains).  (J. Michael Bowers. et al. Foxp2 Mediates Sex Differences in Ultrasonic Vocalization by Rat Pups and Directs Order of Maternal Retrieval. The Journal of Neuroscience, February 20, 2013; Vol. 33, Issue 8:pages 3276 %u20133283 DOI: 10.1523/JNEUROSCI.0425-12.2013)