Adults who learn a new language may find reading and listening to their target language easier than producing speech, according to a recent study in the Journal of Neuroscience. In the study, researchers from the Basque Center on Cognition, Brain, and Language conducted fMRI experiments on 48 Spanish adults who were learning another language in order to observe brain activity during a series of comprehension and production tasks.
“The human propensity for language requires a delicate balance between neural specialization and capacity for re-organization, making language learning the ideal candidate for examination of specialization and plasticity in the human brain,” the paper reads.
Children, unlike adults, are widely known to use both hemispheres of the brain in language development; this plasticity—the brain’s ability to use various regions to perform the same task—contributes to the ease young children generally have in picking up a first or even second language. As we age, the different hemispheres of the brain become more specialized for certain tasks, a process known as lateralization.
Common knowledge has it that the left hemisphere stores most of our linguistic faculties, however this study suggests that this idea is an oversimplification.
The researchers conducted two separate experiments, one focused on native Spanish speakers who were learning Basque at either a beginning or advanced level and the other on bilingual Spanish and Basque speakers with an intermediate proficiency in English. In both sets of experiments, they found differences in which regions of the brain were activated during production and comprehension tasks.
During speech production tasks, the researchers found that regions in the left hemisphere of the brain were activated. However, when participants did the listening and reading comprehension tasks, there did not appear to be a consistently dominant hemisphere across each participant—it varied quite a bit between individuals.
With beginners, they also found that participants in the study tended to activate the same regions of the brain for comprehension in both their native and target language. As speakers advanced in the language, however, comprehension lateralized such that the non-native language was stored in the opposite side of the brain from the native language. This same process did not occur for speech production, however.
Because speaking appears to be very strongly lateralized to the left side of the brain, the researchers suggest that it may be easier for adults to pick up languages with a similar phonology to their native language. Likewise, due to the fact that comprehension involves a more flexible, child-like neuroplasticity, adults may find that their reading and listening skills progress more quickly than their speaking skills.
“These convergent results shed light on the long-standing debate of neural organization of language by establishing robust principles of lateralization and plasticity of the main language systems,” the paper reads.