Dual mechanisms of cognitive control in bilinguals and monolinguals

Abstract

Growing evidence shows that executive functioning benefits from bilingual experience. However, the nature of the mechanisms underlying this advantage remains to be clarified. Whereas some have put forward single process accounts to explain the superior performance of bilinguals relative to monolinguals in executive control tasks, recent findings have been interpreted by considering the dynamic combination of monitoring and inhibitory processes to overcome interference from distractor information. In the present study we explored this idea by comparing monolinguals and highly proficient bilinguals in the AX-CPT. This task requires individuals to adjust proactive (monitoring) and reactive (inhibition) control to achieve efficient performance. We also examined the extent to which a well-known index of inhibitory capacity, the stop-signal reaction time, predicts accuracy in the AX-CPT. Results showed that bilinguals outperformed monolinguals in the experimental condition where higher requirement of proactive-reactive control adjustment was required. Interestingly, the inhibition index predicted errors in this condition only in the sample of bilinguals. These findings suggest that a better understanding of the cognitive benefits of bilingualism may require consideration of how bilinguals adjust different executive control mechanisms to cope with interference.

Keywords:

• Monitoring
• Inhibition
• Cognitive control
• Bilingualism

This research was supported by grants EDU2008-01111, CSD2008-00048, and PSI2008-05607 from the Spanish Ministry of Science and Innovation to the 3 authors, by grant PSI2011-25797 from the Spanish Ministry of Science and Innovation to first and second authors, by grant P08-HUM-3600 from the Andalusian Government and PSI2012-33625 to the third author, and doctoral research grant FPU (AP2007-00314) from the Spanish Ministry of Education and Science to the first author.

Notes

¹ We also performed analyses in which we only included the 19 simultaneous bilinguals, and we obtained similar patterns of results. Thus, the ANOVA on accuracy showed that the interaction of Group × Type of trial was significant, F(2, 76) = 3.29, MSE = .19, p = .043, η_p² = .08, with the monolinguals producing significantly more “yes” (incorrect) responses to AY trials than the bilinguals, F(1, 38) = 3.31, MSE = .042, p = .077, η_p² = .08. Similarly, the ANOVA on RT showed significant main effects of group, F(1, 38) = 3.91, MSE = 23910, p = .05, η_p² = .093 (monolinguals were faster than the bilinguals), and type of trial, F(2, 76) = 248.15, MSE = 2391, p < .001, η_p² = .87, with AY trials producing slower responses that AX or BY trials. Finally, the comparisons between monolinguals and bilinguals on [p(respond/signal)] and SSRT were no significant, Fs(1, 38) < 1, and the correlation between SSRT and AY errors in the bilinguals was r = .49, p = .04.