CINCINNATI - Many people recognize that the majority of women talk a lot, and a whole lot more than the average man, but it's never been known exactly why.
A new study conducted at the University of Maryland that was published in The Journal of Neuroscience examined a protein called Foxp2 that might help to explain the difference between communication styles in men and women.
Sex differences in early language acquisition and development in children are well documented — on average, girls tend to speak earlier and with greater complexity than boys of the same age, according to the study.
However, scientists continue to debate the origin and significance of such differences. Previous studies showed the Foxp2 protein plays an important role in speech and language development in humans and vocal communication in birds and other mammals, according to the study.
Researchers looked at the levels of Foxp2 protein in the brains of 4-day-old male and female rats to compare the distress calls made by the rats when they were separated from their mothers and siblings, according to the study.
Compared with females, males had more of the protein in brain areas associated with cognition, emotion, and vocalization, according to the study.
The male rats made more noise than females — producing nearly double the total vocalizations over the five-minute separation period — and were preferentially retrieved and returned to the nest first by the mother, according to the study.
Researchers then reduced the levels of Foxp2 protein in the male rats and increased it in the female rats.
When they did this, researchers found that the rats actually reversed the sex difference in the distress calls, which caused the females to sound like males and the males to sound like females, according to the study.
"This study is one of the first to report a sex difference in the expression of a language-associated protein in humans or animals," Margaret McCarthy, a researcher at the University of Maryland, said. "The findings raise the possibility that sex differences in brain and behavior are more pervasive and established earlier than previously appreciated."
Researchers then conducted a study with a small group of children to look at the different levels of Foxp2 protein in their brains.
They found that unlike the rats, where Foxp2 protein was higher in males than females, it was the opposite in the case of humans. Girls had higher levels of Foxp2 protein in their cortex, the brain region associated with language, than their male counter parts.
"At first glance, one might conclude that the findings in rats don't generalize to humans, but the higher levels of Foxp2 expression are found in the more communicative sex in each species," noted Cheryl Sisk, who studies sex differences at Michigan State University and was not involved with the study.