Effects of non-native language exposure on the semantic processing of native language in preschool children.

We investigated the effects of non-native language (English) exposure on event-related potentials (ERPs) in first- and second-year (four- and five-year-old) preschool Japanese native speakers while they listened to semantically congruent and incongruent Japanese sentences. The children were divided into a non-native language exposed group (exposed group) and a group without such experiences (control group) on the basis of their exposure to non-native language. We compared the ERPs recorded from the two groups in each of the two preschool years. N400 was observed both in the first- and second-year preschoolers. Differences owing to exposure to non-native language appeared in the second-year preschoolers but not in the first-year preschoolers. In the second-year preschoolers, the N400 onset in the exposed group was shorter than that in the control group, but there was no difference in the N400 offset between the exposed and control groups. Furthermore, the scalp distribution of the N400 in the exposed group was broader than that in the control group. These results indicate that the time course and scalp distribution of semantic processing for native language sentences in young children fluctuated depending on exposure to non-native language.