Effect of second language exposure on brain activity for language processing among preschoolers

We investigated brain activity in 3–5-year-old preschoolers as they listened to connected speech stimuli in Japanese (first language), English (second language), and Chinese (a rarely exposed, foreign language) using near-infrared spectroscopy. Unlike the younger preschoolers who had been exposed to English for almost 1 year, brain activity in the bilateral frontal regions of the older preschoolers who had been exposed to English for almost 2 years was higher for Japanese and English speech stimuli than for Chinese. This tendency seemed to be similar to that observed in adults who had learned English for some years. These results indicate that exposure to a second language affects brain activity to language stimuli among preschoolers.

► Preschoolers had been exposed to L2 for almost 2 years.
► Their brain activity was higher for L1 and L2 than for an unexposed L3.
► A similar tendency was observed in adults exposed to L2 for some years.
► Changes in brain activity for language stimuli can occur among preschoolers.