If you’ve ever tried picking up a new language as a teenager or adult, you’ll know it gets harder the older you become. New research has now verified this long-standing idea and even discovered the “critical window” in a person's life where learning a second language is easiest.

Cognitive scientists working at Boston College, MIT, and Harvard have found that the brain is best equipped to learn a second language before the age of 17.4 years. After you pass this age, you will theoretically never be able to speak as fluently as a native speaker.

You’ll be pleased to hear that this “critical window” is actually a decade longer than scientists previously thought. However, the reality remains that your ability to learn a new language will dramatically weaken after you hit the 17 to 18 years of age mark. Yep, being an adult sucks.

“It was surprising to us. The debate had been over whether it declines from birth, starts declining at 5 years old, or starts declining starting at puberty,” Joshua Hartshorne, an assistant professor of psychology at Boston College, said in a statement.

Reporting in the journal Cognition, the researchers explain how they gathered data from about 700,000 English-speaking people who took part in a viral Facebook quiz called “Which English?” Users were asked their age and their language history, followed by a string of questions on grammar.

Scientists remain unsure why this decline occurs, although they believe the change could be explained by social factors or perhaps by a decline in brain plasticity, the ability of the brain to modify its connections or rewire itself.

“It’s possible that there’s a biological change. It’s also possible that it’s something social or cultural,” added Josh Tenenbaum, an MIT professor of brain and cognitive sciences. “There’s roughly a period of being a minor that goes up to about age 17 or 18 in many societies. After that, you leave your home, maybe you work full time, or you become a specialized university student. All of those might impact your learning rate for any language.”

The team has posted all of their raw data online in the hopes of other scientists finding out more about this issue. Additionally, they hope this work could lay the foundations for research in other far-reaching fields beyond cognitive sciences.

"Explaining this 'critical period for language acquisition' is crucial not only for understanding why humans, but not animals or machines, learn language, but also for research questions on neural development and plasticity, bilingual education, foreign language education, treatment of disorders that affect language, and early childhood stimulation," added Hartshorne.