They knew they needed at least half a million participants, so they found a way to make it work. This is how they gathered this unprecedentedly large dataset.
“It’s been very difficult until now to get all the data you would need to answer this question of how long the critical period lasts,” says Josh Tenenbaum, an MIT professor of brain and cognitive sciences and an author of the paper. “This is one of those rare opportunities in science where we could work on a question that is very old, that many smart people have thought about and written about and take a new perspective and see something that maybe other people haven’t.”
While it was common knowledge that children are much faster at learning foreign languages, narrowing down the specific interval is very important, for instance, for deciding when kids should start learning a new language. Researchers found that the grammar-learning ability remains strong until age 17 or 18, after which it starts to decline — which was rather unexpected.
“It was surprising to us,” Hartshorne says. “The debate had been over whether it declines from birth, starts declining at 5 years old, or starts declining starting at puberty.”
However, it’s not clear why the decline starts to happen. It may either be a cultural factor (as they become adults, children might tone down their learning rate) or a biological one, as we already know that the brain starts to lose some of its plasticity around that age.
Still, you shouldn’t let this discourage you. Even if it’s a bit harder (or even because it’s a bit harder), learning a foreign language can be very rewarding — and also useful. It’s not just the ability to talk to someone from another country, studies have shown that learning a second or third language does wonders for your brain and mental health. Furthermore, some research suggests that even when you’ve forgotten a language, you haven’t really forgotten it.
The study has been published in the journal Cognition.