A new study reveals the age at which the human brain, on average, stops being the amazing linguistic sponge we’re all born with.

The short answer is about age 18 but, for best results, you should start learning a new language by age 10.

The interesting back story on this study is how it was conducted. Participation was essentially crowdsourced on the internet, by offering a short survey that measured facility with English subtleties. Investigators were then able to determine, on a statistical basis, the age at which language acquisition begins to decay.

Another innovative feature: based on your response, the survey predicts your dialect of English. This incentive, combined with easy access worldwide and the fact that the survey went viral on Reddit and Facebook, led to unheard of participation levels.

You can take the test yourself at Which Engish?.

children are proficient at learning a second language up until the age of 18, roughly 10 years later than earlier estimates. But the study also showed that it is best to start by age 10 if you want to achieve the grammatical fluency of a native speaker