The results among the first to link brain differences to language learning aptitude in healthy people, says Narly Golestani at University College London, UK. “The bigger picture is that we’re starting to understand that brain shape and structure can be informative about people’s abilities,” she says.
Those in the study who were quickest to hear subtle differences in sounds from a foreign language were found to have the greatest amount of white, fatty tissue in a brain region responsible for sound processing.
“It could be that this translates into greater efficiency in the brain,” comments Adam Brickman, who researches brain structure the Columbia University Medical Center in New York.
Scientists’ understanding of white matter has improved recently, he says, thanks to better brain scanning technology. The fatty tissue provides insulation and enables signals to travel faster through nerve fibres. In contrast, the grey matter of the brain contains neurons without this protective layer.
Da da da
The study involved 65 French adults aged between 21 and 30, none of whom had any substantial foreign language skills. These participants were asked to distinguish the French ‘da’ sound, similar to that in the word dad’, from the Hindi ‘da’ sound, which resembles that in the word ardent’. The tongue is positioned near the upper teeth to make the French sound and at the roof of the mouth to make the Hindi sound.
Golestani notes that the difference between the sounds is subtle, existing only in the first 40 milliseconds. The fastest learned to spot the difference within 8 minutes, while the slowest were still guessing randomly after 20 minutes.
Then, the 11 fastest and 10 slowest learners were given brain scans using magnetic resonance imaging (MRI). The researchers focused their analysis on a region of the brain called Heschl’s gyrus, which helps to process sound.
The brain scans revealed that the fastest learners had, on average, 70% more white matter in the left Heschl’s gyrus than the slowest learners. They also showed a 3.2-fold difference between the fast learner with the most amount of white matter and the slow learner with the least amount of white matter.
“That seems like a pretty large difference,” says Brickman, adding that the more white matter could make it easier for information to flow to and from Heschl’s gyrus. “The interest in studying white matter is that it helps us to understand how regions of the brain connect.”
Golestani stresses the results only deal with a person’s ability to understand foreign language sounds and do not relate to other aspects of language, such as grammar.
She says further tests are needed to explore whether the brain difference is genetically predetermined or a result of experience and environment. The team is currently testing phoneticians, people who specialise in studying different language sounds, to see if the white matter in their brains correlates with the length of their training.