Juggling two languages in one mind. What bilinguals tell us about language processing and its consequences for cognition

Psycholinguistics has traditionally focused on language processing in monolingual speakers. In the past two decades, there has been a dramatic increase of research on bilingual speakers, recognizing that bilingualism is not an unusual or problematic circumstance but one that characterizes more language speakers in the world than monolingualism. Most critically, cognitive scientists and neuroscientists have come to see that understanding the way that bilinguals negotiate the presence of two languages in the mind and brain may reveal processes that are otherwise obscured in monolingual speakers. In this chapter, we review the new research on language processing in bilinguals. Our starting point is the observation that both languages are active when bilinguals intend to use one language alone. The parallel activation of the two languages creates competition across the two languages, which renders the bilingual a mental juggler. Surprisingly, the resolution of cross-language competition imposes relatively few processing costs to bilinguals because they appear to develop a high level of cognitive control that permits them to switch between the two languages and, at the same time, effectively select the intended language with few errors. The expertise that bilinguals develop in juggling the two languages has consequences for language processing, because both the native and second languages change as bilingual skill is acquired, and also for domain general cognitive processes, with the result that executive function is enhanced in bilinguals relative to monolinguals. We suggest that recent research on language and cognitive processing in bilinguals requires important revisions to models of language processing based on monolingual speakers alone. In this way, bilingualism is not only an interesting phenomenon in its own right, but an important tool for cognitive and language scientists.