Three discoveries about bilingualism

Kroll, J. F., Dussias, P. E., Bice, K., & Perrotti, L. (2015). Bilingualism, mind, and brain. Annu. Rev. Linguist., 1(1), 377-394.‏

http://www.annualreviews.org/doi/pdf/10.1146/annurev-linguist-030514-124937

This is an interesting rewiew in the new journal Annual Reviews of Linguistics.

For the purposes of this review, bilinguals are people who use more than one language actively and daily.  Bilingualism can occur in many different ways.  Early bilinguals are exposed to two languages from birth and continue to use both languages throughout their lives.  Late bilinguals acquire their 2^nd language only after early childhood, after their mother tongue has been firmly established. Both kinds of bilinguals can live in different environments: an environment in which their native language is dominant, an environment in which their 2^nd language is dominant or a bilingual environment.  A person who is bilingual in Hebrew and English (languages that differ greatly in their structure and their written scripts) is not like a person who is bilingual in English and Spanish or Hebrew and Arabic (Hebrew and Arabic are similar in syntax, grammar and vocabulary but not in written script).  Thus, there are large differences between bilinguals, depending on the age of acquisition of the 2^nd language, the extent to which each language is used, the environment one lives in, and the differences in the languages themselves.

Three discoveries about bilingualism have been made in the past few years.  These discoveries are true for all bilinguals, and they have shaped current research in this field:

1.     When bilinguals use one language, both languages are always activated.  When bilinguals listen to speech, read words and plan speech in either language – both languages are activated.   This means that the language the person is not using at that moment affects the language he is using, even when he is not aware of it.  Another implication is that both languages compete for cognitive resources, and that bilinguals have to control or regulate this competition so as not to wrongly use the language they didn't mean to use, and to preserve the fluency in the language they are using at the moment.  For this to happen, they have to be able to inhibit, at least to some extent, the language not being used at the moment (although it's still activated).

2.    Obviously the native language affects the 2^nd language.  But it seems that the 2^nd language (when we have good proficiency in it) also affects the native language!  This means that bilinguals don't function as two monolinguals.  The languages are not represented in the brain separately.  The interactions between the languages are bidirectional.  These interactions change the way bilinguals process each language.  Thus, bilinguals differ from monolinguals in the mother tongue too.

When a bilingual has to choose between two words or two syntactical/grammatical structures, one of which exists in both languages and the other exists only in one of the languages, he will usually prefer the structure or the word that exists in both languages.  As proficiency in the 2^nd language grows, the preferential use of structures or words that exist in both languages grows.  This is an example of one of the ways bilingualism changes the way we use each language.

3.    Using two or more languages has consequences that go beyond language processing.  It affects cognitive abilities in general.  Life as a bilingual affects a person's general ability to ignore irrelevant information, to switch between tasks and to resolve conflicting cognitive alternatives.

Brain scans of bilingual and monolingual Alzheimer’s patients who were matched for disease symptoms revealed that the brains of the bilingual patients were more diseased than those of monolingual patients. This comparison suggests that the active use of two languages protects bilinguals from the symptoms of the disease.  The researchers estimated that the bilingual patients were diagnosed with  Alzheimer's  4-5 years later than the monolingual patients. 

In many bilingual communities, speakers regularly switch from one language to another, often several times in a single utterance. This phenomenon is called code switching.  Code switching is a normal feature of bilingualism.  The ability to engage in fluent code switching is a hallmark of high proficiency in two languages, given that successful and fluent code switching requires a high degree of knowledge of and sensitivity to the grammatical constraints of both languages.

Code switching skills may benefit bilinguals' general cognitive abilities (I guess these skills can have a beneficial effect on executive functions, which require cognitive flexibility and set switching).  Indeed, bilinguals are more effective than monolinguals at conflict resolution within or across languages or within purely cognitive tasks.