学进去

A crucial period for learning the rules and structure of a language lasts up to around age 17 or 18, say psychologist Joshua Hartshorne of MIT and his colleagues.

Previous research had suggested that grammar-learning ability developed in early childhood before hitting a dead end around age 5. However, Hartshorne’s team reports online in Cognition that people who started learning English as a second language in an English-speaking country by age 10 to 12 ultimately mastered the new tongue as well as folks who had learned English and another language at the same time from birth. Both groups, however, fell somewhat short of the grammatical fluency displayed by English-only speakers. After ages 10 to 12, new-to-English learners reached lower levels of fluency than those who started learning English at younger ages because time ran out when their grammar-absorbing ability fell starting around age 17.

Aiming for a sample of tens of thousands of volunteers, Hartshorne began by contacting friends on Facebook to take an online English grammar quiz, which used a person’s responses to guess his or her native language and dialect (方言) of English. Then volunteers filled out a questionnaire asking where they had lived, languages they had spoken from birth, the age at which they began learning English and the number of years they had lived in an English-speaking country.

In the end, the researchers analyzed responses of 669,498 native and nonnative English speakers. Statistical calculations focused on estimating at what ages people with varying amounts of experience peaking English reached peak grammar ability.

Researchers who study language learning regard the new study as fascinating, but exploratory. According to psycholinguist David Barner of the University of California, San Diego, Hartshorne’s team can’t yet say that language skill develops along a single timeline. Different elements of grammar, such as using correct word order or subjects and verbs that agree with one another, might be learned at different rates, Barner says. It’s also unclear whether the responses of volunteers to an online, 132-item grammar test reflect how well of poorly they actually speak English, he says.

What’s more, language learning involves more than a crucial period for acquiring grammar, cautions linguist David Birdsong of the University of Texas at Austin. For instance, growing up speaking two languages at once puts still poorly understood burdens on the ability to grasp grammar, he says.

In the new study, people who were bilinguals from birth fell short of peak English grammar scores achieved by English-only speakers. That’s consistent with evidence that bilinguals cannot easily turn off one language while speaking another, Birdsong says. Interactions between tongues spoken by one person may slightly depress how much can be learned about both languages, even if bilingual communication still reaches high levels, he suggests.