The modulatory role of second language proficiency on performance monitoring: evidence from a saccadic countermanding task in high and low proficient bilinguals.

We compared Hindi-English bilinguals differing in their L2 proficiency on a saccadic countermanding task which taps inhibitory control as well as monitoring. We particularly explored whether response inhibition and performance monitoring within the oculomotor domain are affected by language proficiency in bilinguals. There were two different oculomotor redirect tasks: Visually Guided Redirect (VGR) task (Experiment1) and Memory Guided Redirect (MGR) task (Experiment 2). In the redirect task, typically a target is presented and the subject is required to make a saccade (no-step trials), unless a new target appears on a different location after some delay from the first target onset (step trials). On such trials participants are required to inhibit and cancel the saccade to the first target and programme a saccade to the new target. Using trial switch reaction time (TSRT), the time taken to inhibit the initiated saccade to the first target as a measure of response inhibition and post-step slowing as a measure of performance monitoring. The results showed the high proficient bilinguals displayed more post-step slowing on the no-step trials as compared to the low proficient bilinguals for both VGR and MGR versions of the task. Secondly, both the high and low proficient bilinguals exhibited comparable TSRT in both VGR and MGR task, showing no modulatory effects of language proficiency on the response inhibition. These results suggest that language proficiency may have an effect on performance monitoring, but not the inhibitory control per se. Thus, we infer that higher proficiency may lead to superior cognitive flexibility and an ability to adjust behavior that facilitates the attainment of the cognitive goal. These findings are in consonance with other current studies that suggest a top-down effect of bilingualism on action control systems.