Multilingual people have trained their brains to learn languages, making it easier to acquire more new languages after mastering a second or third. In addition to demystifying the seemingly herculean genius of multilinguals, researchers say these results provide some of the first neuroscientific evidence that language skills are additive, a theory known as the cumulative-enhancement model of language acquisition.

«The traditional idea is, if you understand bilinguals, you can use those same details to understand multilinguals. We rigorously checked that possibility with this research and saw multilinguals’ language acquisition skills are not equivalent, but superior to those of bilinguals,» said Professor Kuniyoshi L. Sakai from the University of Tokyo, an expert in the neuroscience of language and last author of the research study recently published in Scientific Reports. This joint research project includes collaboration with Professor Suzanne Flynn from the Massachusetts Institute of Technology (MIT), a specialist in linguistics and multilanguage acquisition, who first proposed the cumulative?enhancement model.

Neuroscientists measured brain activity while 21 bilingual and 28 multilingual adult volunteers tried to identify words and sentences in Kazakh, a language brand new to them.

All participants were native speakers of Japanese whose second language was English. Most of the multilingual participants had learned Spanish as a third language, but others had learned Chinese, Korean, Russian or German. Some knew up to five languages.

Fluency in multiple languages requires command of different sounds, vocabularies, sentence structures and grammar rules. Sentences in English and Spanish are usually structured with the noun or verb at the start of a phrase, but Japanese and Kazakh consistently place nouns or verbs at the end of a phrase. English, Spanish and Kazakh grammars require subject-verb agreement (she walks, they walk), but Japanese grammar does not.

Instead of grammar drills or conversation skills in a classroom, researchers simulated a more natural language learning environment where volunteers had to figure out the fundamentals of a new language purely by listening. Volunteers listened to recordings of individual Kazakh words or short sentences including those words while watching a screen with plus or minus symbols to signal if the sentence was grammatically correct or not. Volunteers were given a series of four increasingly difficult listening tests while researchers measured their brain activity using functional magnetic resonance imaging (fMRI).

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