Cognitive control ability mediates prediction costs in monolinguals and bilinguals

In this study, we examined the role that cognitive control and language regulation ability play in mediating readers' susceptibility to prediction error costs when reading in the native language (L1) or a second language (L2). Twenty-four English monolinguals (Experiment 1) and 28 Chinese-English bilinguals (Experiment 2) read sentences in English while their EEG was recorded. The sentences varied in the predictability of an upcoming expected word and in whether that prediction was confirmed. Monolinguals showed sensitivity to sentence contexts in which expectations were not met (i.e., when unexpected words were encountered) in the form of a late, frontally-distributed positivity, but for bilinguals this effect was more complex. For both groups, performance on the prediction task was modulated by individual differences on the AX-CPT, a measure of inhibitory control. However, the bilinguals' reading performance in the L2 was affected not only by inhibitory control, but also by their performance on an L1 verbal fluency task that indexed language regulation and production capability, related to their language dominance and immersion context. Bilinguals with better regulation of the L1 generated a larger frontal positivity in response to unexpected words in the L2, an effect that was attenuated by inhibitory control ability. In contrast, bilinguals with lower regulatory ability generated a larger, late negativity, which was also mediated by control. These findings suggest that the ability to regulate the native language when immersed in a second language environment can influence mechanisms underlying the prediction process when reading in the L2. In addition, cognitive control ability, specifically inhibitory control, appears to mediate the difficulty readers incur when predictions are disconfirmed, not only in the native language, but also for proficient bilinguals reading in the L2. We argue that the mechanisms engaged during prediction in the L1 and L2 are fundamentally the same, and that what differs for bilinguals are the additional demands imposed by their language experience and language use.