Language and tool use seem to be governed by the same brain region, suggests a study involving an fMRI scanner
Practising a tool-using task helps people do better in a test of complex language understanding – and the benefits go the other way too.
The crossover may happen because some of the same parts of the brain are involved in tool use and language, says Claudio Brozzoli at the National Institute of Health and Medical Research in Lyon, France.
One idea is that language evolved by co-opting some of the brain networks involved in tool use. Both abilities involve sequences of precise physical movements – whether of the hands or of the lips, jaws, tongue and voice box – which must be done in the right order to be effective.
Brozzoli’s team asked volunteers to lie in a brain scanner while carrying out tasks involving either tool use or understanding complex sentences.
The tool-based task involved placing small, key-shaped pegs into a tray of holes using a pair of long pliers, while viewing the hands through an arrangement of mirrors. The language test involved understanding sentences such as: “The writer that the poet admires writes the paper.”
During both tasks, the fMRI scanner showed higher activity in small structures deep in the brain called the basal ganglia. The pattern of activity was similar during both tasks.
To see how the two activities affect each other, new groups of volunteers were asked to do tool-use and language tasks, sometimes with similar but less complex tasks switched in for comparison.
For instance, to see how tool use influenced language comprehension, 52 people did two complex language tasks. In between the two language tasks, half the group did the pegs and pliers task, and their scores on the second language task were, on average, about 30 per cent higher than on the first language task.
The other half of the group did a simpler physical task between the two language tests – simply inserting the pegs with their hands. Their scores on the second language tests were also higher than on the first test, but only by about 15 per cent on average.
There was a similar benefit if people did two rounds of tool use interspersed with the complex language task. Here the comparison group did a working memory task between tool use.
“People’s abilities may improve because brain cells in the basal ganglia start working more efficiently and become primed for activity,” says Brozzoli. His group is investigating if the same task using pliers and pegs can help teenagers with language difficulties improve their speech.
Gillian Forrester at Birkbeck, University of London, who wasn’t involved in the work, says the findings fit well with existing ideas of how language may have evolved and how it develops during childhood.
“It is high time we bring the association of motor and cognitive function to the forefront of research, so we can better understand how we became the walking, talking, tool-using great apes we are today,” she says.
Journal reference: Science, DOI: 10.1126/science.abe0874
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