Alison R. Shell (University of Maryland, College Park) & L. Robert Slevc (University of Maryland, College Park)
ashell@umd.edu
Bilingualism; Language production; Inhibitory Control; Language Switching; Dual task
An influential account of how bilingual speakers manage interference between languages is the inhibitory control (IC) model [1], which proposes that bilinguals rely on domain-general IC mechanisms to suppress the non-target language. Much of the evidence for the IC model is correlational; for example, individuals with higher scores on IC tasks tend to perform better on language-switching tasks (e.g., [2]) and findings of a “bilingual advantage” on IC tasks suggest that bilinguals’ extensive practice in controlling languages may transfer to improved IC abilities (e.g., [3]).
The current experiments aimed to go beyond these correlational findings by assessing language-switching costs while simultaneously manipulating demand on IC. If language switching requires IC, then taxing participants’ limited IC resources should increase language switching costs. In Experiment 1, participants switched between naming pictures in English (L1) and Spanish (L2) while simultaneously performing a Simon arrows task (responding to the direction of an arrow that could appear on either side of the screen while ignoring its location). Surprisingly, language switching costs were reduced during incongruent (vs. congruent) Simon arrow trials; i.e., switching was actually easier when IC was taxed. (Note that a control experiment pairing language switching with a task manipulating perceptual difficulty produced no such interaction, suggesting that these findings did not simply reflect the difficulty of a secondary task).
This reduction in language switching costs during an IC demanding dual task might reflect task prioritization, such that participants tended to prioritize the language task when IC demands were high. Experiment 2 thus used a paradigm requiring only one response, by combining language switching with a picture word interference paradigm, wherein conflict was manipulated via the relationship between to-be-named pictures and simultaneously presented distractor words. This task requires only one response (thus eliminating the possibility for differential task prioritization) and also involves conflict between lexical representations, which may be more analogous to conflict involved in language switching. However, switching costs were again not exacerbated when IC was taxed; if anything, switching was less costly during inhibition-demanding trials (with related distractors).
Experiment 3 tested whether these reduced switching costs in IC demanding contexts reflect conflict adaptation, where high conflict trials can lead to reduced conflict on following conflict trials (cf. [4]). Experiment 3 thus interleaved Simon arrow task trials with language switching task trials. Although conflict adaptation was observed across trials of the Simon arrow task, there was no evidence that this Simon conflict influenced language switching.
Overall, these findings fail to support a straightforward role of IC in bilingual language switching and suggest that language control, at least in the context of language-switching tasks, may not draw on domain-general IC.
References
[1] Green, D. W. Mental control of the bilingual lexico-semantic system. Bilingualism: Language and Cognition, 1(02): 67-81, 1998.
[2] Linck, J. A., Schwieter, J. W., & Sunderman, G. Inhibitory control predicts language switching performance in trilingual speech production. Bilingualism: Language and Cognition, 15(3): 651–662, 2012.
[3] Abutalebi, J., Della Rosa, P. A., Green, D. W., Hernandez, M., Scifo, P., Keim, R., … Costa, A. Bilingualism tunes the anterior cingulate cortex for conflict monitoring. Cerebral Cortex, 22(9): 2076–86, 2012.
[4] Kan, I. P., Teubner-Rhodes, S., Drummey, A. B., Nutile, L., Krupa, L., & Novick, J. M. To adapt or not to adapt: The question of domain-general cognitive control. Cognition, 129(3): 637–51, 2013.
