Scientific literature has been littered with studies over the past 40 years documenting the superior language skills of girls, but the biological reason why has remained a mystery until now.

Researchers report in the journal Neuropsychologia that the answer lies in the way words are processed: Girls completing a linguistic abilities task showed greater activity in brain areas implicated specifically in language encoding, which decipher information abstractly. Boys, on the other hand, showed a lot of activity in regions tied to visual and auditory functions, depending on the way the words were presented during the exercise.

The finding suggests that although linguistic information goes directly to the seat of language processing in the female brain, males use sensory machinery to do a great deal of the work in untangling the data. In a classroom setting, it implies that boys need to be taught language both visually (with a textbook) and orally (through a lecture) to get a full grasp of the subject, whereas a girl may be able to pick up the concepts by either method.

The team was able to pinpoint the differences between the sexes by monitoring brain activity in a group of children (31 boys and 31 girls, ranging in age from nine to 15) using functional magnetic resonance imaging (fMRI) while the kids tackled language tasks. In the exercises, two words were either flashed in front of, or spoken to them; they had to determine whether the pair was spelled similarly (omitting the first consonant, as in "pine" and "line") and whether the words rhymed, such as "gate" and "hate" or "pint" and "mint." In some cases, the words fit neither criterion: "jazz" and "list" being an example.

Study co-author Doug Burman, a research associate in Northwestern University's communication sciences and disorders department, says the team saw greater activity in the so-called language areas of the girls' brains than in those of the boys. The areas included the superior temporal gyrus (implicated in decoding heard words), inferior frontal gyrus (speech processing), and the fusiform gyrus, which helps spell and determine the meaning of words. Activation of the latter two structures, in particular, seemed to correlate with the girls' greater language accuracy.

"For girls, it didn't matter if they heard the word or read the word," Burman says. "It does suggest that girls are learning [language attributes] in a more abstract form, and that's the ideal objective when we're teaching things."

Burman says that his team now plans to research whether girls' edge decreases with age, noting that some previous research suggests that the male sensory "bottleneck" may disappear as boys develop into adults.