Conventional wisdom suggests it may well be easier to learn a second language as a child than as an adult. But for adults who do take the linguistic leap, what sort of factors influence how well they acquire another tongue?
In a new study published this week by the Proceedings of the National Academy of Sciences, researchers from the University of Washington’s Institute for Learning & Brain Sciences (I-LABS) suggest that our genes and brain structure could be linked to how successfully we pick up a second language as adults.
The team wanted to explore why adults’ proficiency levels vary when they “all have the same experience in the same class and they learn [the language] with the same instructions,” explains Ping Mamiya, one of the study’s authors.
Seventy-nine first-year college students who had come to the US from China were studied. Forty-four of them were enrolled in a three-week immersive English language course, and the remaining 35 were used in a control group that did not attend the classes.
The researchers performed brain scans on both groups. They used an MRI technique that tracks the movement of water molecules in the brain and records the changes to the brain’s structure as new connections between neurons are made. The researchers found the higher number of days spent in the class correlated with changes in the structure of white matter (the brain’s communications network), notably in a fiber tract known to be key for language processing. These changes began to drop off once students finished the program.
The team also wanted to determine how genetic variation affected the changes observed in the white matter. Using DNA samples, they found that two specific forms of a particular gene, COMT, were linked to greater activity in the white matter structure in students who attended the language classes.
Genetic factors are an interesting point of study because they can be seen as modulators, says Mamiya. “While our student participants were in the immersion program, their brains were undergoing rapid modifications in response to the instructions. However, the unique variants each individual carries in the DNA sequence influence how his or her brain responds to the instruction in a personal way,” she explains.
Almost half (46%) of the time, the students’ final results could be directly linked to the COMT gene and the changes in their brain structure.
“This is just our initial attempt to study the combined effects of brain and genetic factors on human learning,” admits Mamiya. “We still have more work to do before we can identify other factors that account for the rest of the 54% variance.”