Abstract: Recently, the effect of individual difference on language switching and switching cost has become a focus of many studies. Among the factors involved in the effect, L2 proficiency and age of acquisition are shown to be two important factors. Whilst the switching cost in proficient bilinguals is symmetrical, it is not in non-proficient bilinguals. Similar findings are obtained from bilinguals who acquire L2 early and those who acquire late. Moreover, some studies indicate that the switching cost may result from a system that is outside the word-recognition system in the mental lexicon. That is, inhibitive control also plays an important role in language switching as in general task switching. Previous EEG evidence shows that N2 (about 320 ms) that is usually found in the central frontal areas can be used as an indicator reflecting the top-to-down inhibitive control. In this study, the effect of cognitive flexibility (CF) on language switching was examined in non-proficient bilinguals using EEG method. Thirty non-proficient Chinese-English bilinguals were selected from 119 non-English major undergraduates by the Wisconsin Card Sorting Task (WCST). Among them, 15 participants were scored as high cognitive flexibility (CF), and another 15 were scored as low CF. A 2 (high-CF and low-CF) × 2 (L1 and L2) × 2 (repetition and switch) mixed design was employed. A picture naming task and a semantic-decision task were performed by the participants in order to examine the mechanism of language switching during language production and comprehension, respectively. In experiment 1, an immediate naming paradigm was used, and behavioral data were recorded. In experiment 2, a delayed naming paradigm was used, and only ERPs data were collected. In experiment 3, the participants were required to decide whether the presented word indicated a living meaning by pressing buttons. Both behavioral and ERPs data were obtained. The results showed that: (1) The switching cost in high-CF participants was symmetrical, whereas that in low-CF was not. Meanwhile, the mean amplitude and peak value of N2 was larger significantly in high-CF than in low-CF. (2) For high-CF participants, the peak value of N2 in repetitive language production task was larger in L2 repetitive condition than in L1 repetitive condition. (3) In contrast, the peak value of N2 in repetitive language comprehension task was larger in L1 repetitive condition than in L2 repetitive condition. These results suggest that CF affects language switching and its cost. The capability of inhibitive control have a key role in bilingual’s language switching of language production and comprehension. Language switching and its cost in non-proficient bilinguals result from a system that is outside the word-recognition system in the mental lexicon.

Key words: cognitive flexibility, language production, language comprehension, switching cost, N2