Bilingualism and adult differences in inhibitory mechanisms: Evidence from a bilingual stroop task☆
Introduction
Psycholinguistics and neurolinguistics have focused their investigations with bilinguals on the acquisition, manipulation and loss of the first (L1) and second language (L2). The study of bilinguals communication abilities (and disorders) and particularly the cognitive processes underlying translation from one language to another and switching between languages (Price, Green, & von Studnitz, 1999) has given rise to converging and diverging opinions about how the bilingual lexico-semantic system functions (BLSS). For instance, in word translation, there is no real agreement about how is it that individuals are able to produce a word in the other language rather than merely reading it. The BLSS must then be controlled in order to regulate the participation of the different language systems. In the inhibitory control (IC) model of Green (1998), which builds on the supervisory attentional system model of Norman and Shallice (1980), the notion of a functional control circuit is central. Three basic loci of control are integrated in this model: (1) an executive locus which is an equivalent of the supervisory attentional system used for establishing and maintaining goals; (2) a locus at the level of language task schemas; and (3) a locus within the BLSS itself. According to the IC model, language task schemes compete to control all the outputs from the BLSS. Language task schemes must be established, maintained and controlled in order to speak in one language rather than another or to translate between languages.
Inhibition is also integrated in the theoretical framework developed by Dempster (1992) and Hasher and Zacks (1988) where it is conceptualised as an explanatory mechanism of many cognitive activities. According to them inhibition gates which information will be entered into working memory, control the content of working memory according to the current goal or task requirements, and finally limits response competition.
Even if there is a strong evidence for age related decline in inhibitory functioning, we still know little about the effects of normal ageing on inhibitory functioning in bilingual. In another hand, there is no available data where inhibition is studied in different levels of bilingualism.
Section snippets
Purpose
The aim of this research was to examine the performance of younger and older bilinguals on the Stroop test. The Stroop tasks (French and Arabic versions) used in this study consisted of four conditions presented in a fixed order: word reading (WR), colour naming (CN), and incongruent colour naming of colour words (ICN). A between (interlanguage) language condition for the incongruent colour naming of colour words was specifically designed for this study to further test the bilingual
Research participants
The study sample was composed by bilingual volunteers who participated in an extensive normative study of the Boston Naming Test (BNT). Ninety younger (M age = 30.76 years, range = 21–41) and ninety older (M age = 71.33 years, range = 61–79) were then included. They were divided into six groups (30 subjects in each group) according to their age (younger, older) and their degree of bilingualism (Balanced, French-dominant, and Arabic-dominant). Balanced bilinguals had a difference between the two
Response time analysis
A four-way ANOVA with age group (2) and level of bilingualism (3) being the between-subjects variables and Stroop conditions (3) and versions (2) as within subjects variables. The main effects of age group, level of bilingualism and Stroop conditions were all significant (all p<.001) as was the interaction of all the main effects (p<.001).
To decompose the source of interaction, a series of one-way ANOVAs and Scheffé test were conducted. These revealed that in the older group, French-dominant
Conclusion
Taken together, our data suggest that, as it was previously reported, ageing is accompanied by a decline in the efficiency of inhibitory mechanisms. It appears also that the control of language systems in the unbalanced bilinguals may be asymmetrical. Outcomes of young and older groups tend to demonstrate that the more proficient in a certain language a person is being young, the more proficient he will remain in that language being older. This means that the non-dominant language is more
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This research was supported by the Neuropsychology Unit (Angers, France) and by a grant from the Tunisian National Ministry of Higher Education and Scientific Research.