Chantel S. Prat, Brianna L. Yamasaki, Jose M. Ceballos & Roy Seo (Department of Psychology & Institute for Learning and Brain Sciences, University of Washington)
individual differences; inhibition; executive functioning; bilingualism; language similarity; language use
Language is one of the most complex feats of the human mind and brain, involving the retrieval and manipulation of symbols to produce a nearly infinite set of communicative structures. Bilingualism greatly increases these demands, as two sets of symbols, and two sets of rules for manipulating them, must be “managed” in one brain. Much research has been devoted to measuring the broader implications that these demands have for bilingual cognition. For example, a plethora of research has shown that bilinguals exhibit superior inhibitory control to monolinguals, suggesting that the additional demands associated with bilingual language control train general executive processes (see Bialystok, Craik, & Luk, 2012 for a review). Recently, however, these findings have been called into question (e.g., Paap & Greenberg, 2013). We argue that an improved understanding of the facets of bilingualism that likely drive the neurocognitive demands associated with bilingual language control (e.g., language similarity and language use habits) should be central to this research, as it has been widely acknowledged that bilingualism is not a dichotomous variable. In the current experiment, we investigated individual differences in inhibitory control in a total of 423 individuals with bilingual backgrounds. Participants were included if they indicated having experience with two or more languages on a language history questionnaire. Data from the same version of a Simon Task were pooled from three investigations of executive functioning. The Simon Effect (a metric of inhibitory control) was indexed by subtracting incongruent reaction times (RTs) and accuracies from congruent ones, although all significant results were from RT indexes. The primary independent variables of interest were linguistic distance (Chiswick & Miller, 2005), and current language usage, calculated as the percentage of time over the past month that participants used their dominant language (lower numbers indicate more balanced bilinguals). We also correlated second language (L2) age of acquisition and proficiency with inhibitory control. The results showed that linguistic distance was correlated with the Simon Effect, [r(191) = .32, p < .001], suggesting that individuals who speak languages that are distantly related have better inhibitory control. Additionally, language use was positively correlated with the Simon Effect, [r(423) = .114, p = .019], suggesting that individuals who use both languages regularly have better inhibitory control. Finally, both age of L2 acquisition and L2 proficiency significantly correlated with the Simon Effect [r(268) = .15 and -.14 respectively, ps = .018 and .025 respectively), with early and more proficient bilinguals exhibiting better inhibitory control. The results of this exploratory analysis demonstrate the importance of not treating bilingualism as a homogeneous category, and highlight the significance of two largely understudied features, language similarity and language use, on indices of inhibitory control.
 Bialystok, E., Craik, F. I., & Luk, G. Bilingualism: consequences for mind and brain. Trends in cognitive sciences, 16(4), 240-250, 2012.
 Paap, K. R., & Greenberg, Z. I. There is no coherent evidence for a bilingual advantage in executive processing. Cognitive Psychology, 66(2), 232-258, 2013.
 Chiswick, B. R., & Miller, P. W. Linguistic distance: A quantitative measure of the distance between English and other languages. Journal of Multilingual and Multicultural Development, 26(1), 1-11, 2005.