The Impact of Bilingualism on Conflict Control

Abstract

In recent years, a substantial amount of research has been published on the bilingual advantage hypothesis in executive functions, according to which the continuous and consistent experience of managing two languages leads to cognitive gains, particularly in cognitive control functions related to conflict monitoring and resolution. Researchers have presented evidence that bilinguals exhibit significantly smaller conflict effects than monolinguals, as well as overall faster reaction times in both congruent and incongruent trials. The former are interpreted as evidence of the benefits of bilingualism to inhibitory control, while the latter are seen as evidence of bilinguals’ advantage in conflict monitoring processes. Nevertheless, there have also been an extensive number of studies reporting no bilingual advantage in conflict monitoring and/or resolution, which have thrown doubts on the existence of a bilingual advantage. It has been proposed that the elusiveness of the bilingual advantage may be due to: features of the bilingual experience —such as proficiency in the second language or frequency of use of both languages— which may restrict or boost bilinguals’ performance in conflict control tasks; poor control of confounding variables, such as socio-economic status, which have considerable impacts on the development of executive functions; or insufficient statistical power of some of the studies, since most studies showing a bilingual advantage were performed with smaller numbers of participants per group, while studies with large n’s tend to show null results. It has therefore been proposed that the bilingual advantage hypothesis may be unsustainable. We set out to contribute to this area of research, by comparing the performance of a group of bilingual participants with a control group of monolinguals in two tasks measuring different mechanisms of conflict monitoring and resolution —the Simon task and the Attention Network Test. Our main goals were to investigate: (a) whether a bilingual advantage was to be found in conflict control tasks requiring both interference control and suppression of a prepotent response; (b) whether this bilingual advantage, if present, stemmed from an improved inhibition control mechanism or from a more efficient monitoring function; (c) whether general individual-difference variables and/or bilingualism-specific variables could be responsible for boosting or restricting the bilingual advantage. Participants completed two executive control tasks —a Simon task and an Attention Network Test—, as well as an English proficiency test, a fluid intelligence task, a Language History Questionnaire, a Socio-Economic Status Questionnaire, and a Questionnaire on Activities with an Impact on Executive Functions. Our results in both the Attention Network Test and the Simon task, in reaction times as well as in accuracy rates, showed no differences between monolinguals and bilinguals in any of the measures analysed: overall reaction times, overall accuracy rates, conflict effects, alerting effect, orienting effect, sequential congruency effects, and working memory costs. Moreover, our analyses have identified age, fluid intelligence and gender as variables that have a significant effect in the performance of both groups of participants in these tasks. Additionally, none of the variables specific to bilingualism showed a statistically significant effect on any of the measures analysed, when controlling for age, fluid intelligence, and gender. We interpret our results as evidence against a bilingual advantage in conflict monitoring and resolution. The results obtained in our study are discussed in relation to the broader literature on bilingualism and cognition and current theories of conflict monitoring and control. We finish by presenting a hypothesis according to which intense and rich language processing experience may be a better predictor of cognitive control than bilingualism, and that it may, in fact, act as a mediator in the relationship between bilingualism and cognitive control. We draw on research showing a consistent link between cognitive control and language processing, by an activation of the same neural area —the left inferior frontal gyrus. We also address the question of how this hypothesis could be tested.