Learning languages is a breeze for young children, but once that window of opportunity closes, for adults it becomes notoriously difficult. Now, Spanish scientists have shed more light on how we get around this.
While it’s thought that language is specialised in the left side of the brain, the researchers found that the right side also helps out when learning a new language as an adult, providing further evidence of the brain’s remarkable flexibility.
“The left hemisphere is widely considered to be more or less hardwired for language, but there is plenty of evidence that it is not quite as simple as that,” says Kshipra Gurunandan from the Basque Centre on Cognition, Brain and Language, lead author of a paper published in the Journal of Neuroscience.
This is seen, for instance, in the unpredictable nature of language impairment and recovery after brain damage to either hemisphere, especially in people who are multilingual.
Gurunandan and colleagues noted that adults can memorise lists of foreign or nonsense words but struggle to distinguish or pronounce foreign sounds or tones. They reasoned that this difficulty could arise from non-linguistic, sensorimotor aspects of language.
“Reading, listening and speaking activate common ‘language’ regions in the brain,” Gurunandan explains, “but they also involve the visual, auditory and motor regions, respectively, and we wanted to study the consequences for language learning.”
To test this, they recruited 48 healthy native Spanish speakers aged 17 to 60 from language schools. The study consisted of two experiments: one compared basic and advanced level learners of the Basque language and the second looked at Spanish-Basque natives before and after a three-month language course in intermediate-level English.
The volunteers performed language tasks involving reading, listening and speaking in their native and new languages while their brains were scanned using functional magnetic resonance imaging (fMRI).
While speaking primarily activated language regions in the left hemisphere, results showed much greater variation in which hemisphere was activated while reading and, to a lesser degree, listening. The switch was most apparent in more advanced learners.
This suggests reading and listening are more flexible throughout adulthood, which makes them easier to learn as people become more proficient, according to Gurunandan. It could also explain why adults can often understand a new language but struggle to speak it to the same skill level.
It’s striking, she adds, that the switch from a native language to a new one that’s being actively learned recruits the brain’s left hemisphere but lateralises to both hemispheres with greater proficiency, which might also help people separate the two languages.
The researchers say these insights “have major theoretical and practical implications” for understanding the neural underpinnings of language, clinical patients and language learning in the general population.
Related reading: Children’s brains hear language differently