Little kids can pick up a new language pretty easily. It’s supposed to be far harder for older kids. But that assessment might not be fair. The window on when people can learn the rules and structure of a language well appears to last until around age 17 or 18.
Earlier research had suggested we’re best at learning grammar in early childhood. Then we hit a dead end around age 5. If true, it should affect people who move to another country after their first few years of life and try to then learn a new language. These people should have a hard time ever speaking as well as native speakers.
But that’s not so, say psychologist Joshua Hartshorne and his colleagues. Hartshorne works at Boston College in Massachusetts.
Earlier studies had included too few people who speak only one or two languages, Hartshorne found. There usually included no more than 250 of them, he says. And that, he thinks, made it hard to study the entire timeline of grammar learning.
Hartshorne instead decided to sample of tens of thousands of people. He began by asking friends on Facebook to take an online English grammar quiz. It used a person’s answers to guess his or her native language and dialect of English. (A dialect is a variant of some language — identifiable by how some words are pronounced or by quirks in grammar — that develops within a particular region or social group.) After completing the quiz, volunteers answered questions about where they had lived, the languages they had spoken from birth and the age at which they first started learning English. It also asked how long they’d lived in an English-speaking country.
As he had hoped, people shared the quiz widely across social media. This let Hartshorne’s group analyze responses from 669,498 native and nonnative speakers of English. The researchers used statistics to find out when people with varying English-speaking experiences reached their peak grammar ability.
If people moved to a new country and began speaking English by age 10 to 12, they eventually spoke it as well as folks who had learned both English and another language from birth. But both groups scored a little worse than people who spoke English only, the researchers found.
The quiz results showed that around age 17, people’s ability to learn grammar took a nosedive. And those who started learning English after age 10 or 12 never reached the same level of English proficiency as people who started younger. Why? The researchers think it’s because they had fewer years to practice before their skills dropped off at 17.
But here’s the surprise: Language acquisition did not end at 17. People’s English skills kept improving slightly until around age 30, the new study found. And this was true among both native speakers and those who learned English as a second language. Still, most language learning happened by age 20, the new study concludes.
Hartshorne’s team reports its findings in the August 2018 Cognition.
Language experts find the new study intriguing. Still, they add, it’s just a start. “I see this as a first foray, says David Barner. He’s a psycholinguist (SY-koh-LING-gwizt) at the University of California, San Diego. Such scientists study, among other things, how people learn languages. He says the new study offers “a blast of data.” And while powerful, he says, it also “lacks precision.”
For instance, Hartshorne’s team hasn’t shown that everyone learns languages along the same timeline. For instance, Barner says, people might learn different grammar rules — such as using the correct word order, or subjects and verbs that agree with one another — at different rates. The study used an online test with 132 questions, he adds. It’s unclear how well this type of test actually measures people’s skills at speaking English well.
The researchers also tested no one under 7. So they couldn’t judge how long it really takes to learn English, says Elissa Newport. She’s a psycholinguist at Georgetown University in Washington, D.C. The researchers claim that learning tends to take about 30 years to complete. That leads to their estimate that the most important period ends at age 17. But Newport says hundreds of previous studies (including hers), find that people are largely done learning their native language by age 7. And learning a second language, those studies suggest, goes best when people start by age 5 or so.
What’s more, language learning isn’t just about a grammar window, says David Birdsong. He’s a linguist at the University of Texas at Austin. Growing up speaking two languages at once, for instance, makes it challenging to learn grammar. And researchers don’t understand those challenges well, he adds.
In the new study, people who learned two languages from birth didn’t match the highest grammar scores of English-only speakers. That fits with other evidence, Birdsong says, that it’s hard for those who speak two languages to turn one off while speaking another. Speaking two languages may even limit how much a person can learn about both languages, he says. That might be true even in someone with a good command of both tongues.