Word Workout

PEOPLE who learn second languages as adults build up new brain areas to handle the knowledge, according to new American research. But if you learn two or more languages as a youngster, you incorporate them into the same primary language area, the study suggests.

Joy Hirsch and her colleagues at the Memorial Sloan-Kettering Cancer Center in New fork studied 12 bilingual' people. Six of them-dubbed "early" bilinguals-had learnt two languages in infancy. The other six were "late" bilinguals, who mastered a second language between the ages of 11 and 19. Between them, the volunteers spoke a total of 11 languages, including Korean, Hebrew, Croatian and Japanese.

While her subjects silently "spoke" their two languages in turn, Hirsch used functional magnetic resonance imaging to measure the brain activity In Broca's area in the frontal region of the cortex. In this week's Nature (vol 388, p 171), her team reports that in early bilinguals, both languages lit up the same part of Broca's area. In late bilinguals, however, two discrete regions about 8 millimetres apart were activated.

The findings suggest that a primary language centre integrates all the languages a child is exposed to during an early formative period. But people who learn new languages at a later date have added to their language system, says Hirsch: "We can see the body building in the brain as a result of this."

The findings seem at odds with a study in 1995 using positron emission tomography scans. This suggested that languages are always centred in the same part of Broca's area. However, "late" bilinguals in the 1995 study learnt a second language at an average age of only seven, matching Hirsch's description of an early bilingual.

Alison Motluk

New Scientist July 1997