“The left hemisphere is known as the language-learning part of the brain, but we found that it was the right hemisphere that determined the eventual success”
A new study, “Speech processing and plasticity in the right hemisphere predict variation in adult foreign language learning,” published in NeuroImage, focuses on the roles played by the brain’s left and right hemispheres in language acquisition. The findings could lead to instructional methods that potentially improve students’ success in learning a new language.
The brains of 24 students of were scanned before and after a month-long intensive Mandarin program. University of Delaware cognitive neuroscientist Zhenghan Qi was surprised by the results: “The left hemisphere is known as the language-learning part of the brain, but we found that it was the right hemisphere that determined the eventual success” in learning Mandarin.
“This was new,” she said. “For decades, everyone has focused on the left hemisphere, and the right hemisphere has been largely overlooked.” The left hemisphere is undoubtedly important in language learning, Qi said, noting that clinical research on individuals with speech disorders has indicated that the left side of the brain is in many ways the hub of language processing.
However, according to Qi, during the early stages of language acquisition before people begin processing vocabulary and grammar, they first have to identify its basic sounds or phonological elements. The right side of the brain is key to distinguishing “acoustic details” of sounds.
During the study, the participants were taught in a setting designed to replicate a college language class, although the usual semester was condensed into four weeks of instruction. Students attended class for three and a half hours a day, five days a week, completed homework assignments and took tests.
“Our research is the first to look at attainment and long-term retention of real-world language learned in a classroom setting, which is how most people learn a new language,” Qi said.
By scanning each participant’s brain with functional MRI (magnetic resonance imaging) at the beginning and end of the project, the scientists were able to see which part of the brain was most engaged while processing basic sound elements in Mandarin. To their surprise, they found that the right hemisphere in the most successful learners was most active in the early, sound-recognition stage, although, as expected, the left hemisphere showed a substantial increase of activation later in the learning process.
“It turns out that the right hemisphere is very important in processing foreign speech sounds at the beginning of learning,” Qi said. She added that the right hemisphere’s role then seems to diminish in those successful learners as they continue learning the language.
Additional research will investigate whether the findings apply to those learning other languages, not just Mandarin. The eventual goal is to explore whether someone can practice sound recognition early in the process of learning a new language to potentially improve their success.