This study investigated the relationship between bilingualism and task switching ability using a standardized measure of switching and an objective measure of bilingual language proficiency. Heritage Language (HL) speaking Spanish-English and Mandarin-English bilinguals and English speaking monolinguals completed all four subtests of the Color-Word Interference Test (CWIT), an English verbal fluency task, and a picture naming test (the Multilingual Naming Test) in English. Bilinguals also named pictures in their HL to assess HL proficiency. Spanish-English bilinguals were advantaged in task switching, exhibiting significantly smaller switching cost than monolinguals, but were disadvantaged in verbal fluency and picture naming. Additionally, performance on these cognitive and linguistic tasks was related to degree of HL proficiency, so that increased ability to name pictures in Spanish was associated with greater switching advantage, and greater disadvantage in both verbal fluency and picture naming. Mandarin-English bilinguals, who differed from the Spanish-English bilinguals on several demographic and language-use characteristics, exhibited a smaller but statistically significant switching advantage, but no linguistic disadvantage, and no clear relationship between HL proficiency and the switching advantage. Together these findings demonstrate an explicit link between objectively measured bilingual language proficiency and both bilingual advantages and disadvantages, while also showing that consequences of bilingualism for cognitive and linguistic task performance can vary across different language combinations.
Keywords: Bilingualism; CWIT; Heritage Language; Picture naming; Switching cost; Verbal fluency.