Ability to Learn Languages Stays Strong Until Late Teens, New Study Finds
Scientists have long posited that there is a "critical period" for language learning, but new research suggests that the time frame stretches on much longer than previously thought.
A new study from the Massachusetts Institute of Technology suggests that children remain skilled at learning the grammar of a new language up to the age of 17 or 18, the time at which many students graduate high school. This finding injects new evidence for the decades-long debate over the "critical period" that had centered on whether the decline in language-learning skills begins at age 5 or at the onset of puberty.
However, the same MIT study also found that it is difficult for people to achieve proficiency similar to that of a native speaker unless they start learning a language much earlier, by the age of 10. People who start learning a language between the ages of 10 and 18 will still learn quickly, but since they have a shorter window before their learning ability declines, they're less likely to reach the proficiency of native speakers, the researchers found.
"It takes work on the part of the parents but, as far as the child's concerned, it's quite easy to become bilingual," Joshua Hartshorne, an assistant professor of psychology at Boston College, who conducted this study as a postdoctoral scholar at MIT. "That's when you're best at learning languages. It's not really something that you can make up later."
The work was published today in Cognition, an international journal of cognitive science.
After late teens, grammar-learning ability drops precipitously
While it's typical for children to pick up languages more easily than adults, researchers have struggled to study this phenomenon in laboratory settings. The latest research findings are based on an analysis of results from a 10-minute online grammar quiz with nearly 670,000 participants. The quiz is still active online.
To avoid the costly and time-consuming process of following test subjects as they learn a new language over many years, the researchers tried a different approach: They used the online quiz to measure the grammatical ability of many people of different ages who started learning English at different points in their life, in hopes of gathering enough data to come to some meaningful conclusions.
Hartshorne focused on grammatical rules most likely to confuse a non-native speaker and wrote questions that could trip them up. To entice more people to take the test, he also included questions that were not necessary for measuring language learning, but were designed to reveal which dialect of English the test-taker speaks.
After taking the quiz, users answered questions about their current age and the age at which they began learning English, as well as other information about their language background.
As the results rolled in, the researchers spent nine months developing and testing a variety of models to see which was most consistent with their results. They came to the conclusion that grammar-learning ability remains strong until age 17 or 18, at which point it drops precipitously.
Though adults are still good at learning foreign languages, the chances of reaching the level of a native speaker are slim if they begin learning as a teenager or as an adult. But the research team still does not know what closes the window on the so-called "critical period."
During peer review, critics questioned the design of the study, especially the fact that it was conducted online and that researchers operated under the assumption that learning grammar is "one thing with one critical period."
"There probably is one right way of doing it, but we're so far from understanding language well enough to know for sure what that is," Hartshorne said. "We aren't far enough along to even know whether that's something that needs to be done, much less how to do it."
Hartshorne will embark on several related studies, including one that will compare native and non-native speakers of two additional languages: Spanish and Mandarin. Like English, those two languages have millions of non-native speakers trying to learn the language.
"We're interested in language learning, not specifically English learning," Hartshorne said.
Related Stories on Language Learning
Image Credit: Andrew Echeverria, left, gets help from Joel Miller, a veteran educator who teaches a course for long-term English-learners at Fairfax High School in Los Angeles. The course was created to help students who have struggled to become proficient in English.