"FOXP2" is expressed in many areas of the brain, including the basal ganglia and inferior frontal cortex, where it is essential for brain maturation and speech and language development. In mice, the gene was found to be twice as highly expressed in male pups than female pups, which correlated with an almost double increase in the number of vocalisations the male pups made when separated from mothers. Conversely, in human children aged 4–5, the gene was found to be 30% more expressed in the Broca's areas of female children. The researchers suggested that the gene is more active in "the more communicative sex".