For years there has been a debate in the field of linguistics over whether there is a critical period in a child's development that allows them to better learn new languages. The earlier the better has been the general consensus, but a new study of over half a million people has found children have the ability to grasp a new language for a longer period than previously thought.

In order to gather a large dataset, the team of researchers from Boston College, MIT and Harvard developed a novel Facebook quiz that tested participants' grammar skills, while also gathering information on their language background. To the researchers' surprise the quiz went viral and ultimately gathered data from 669,498 people.

"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, one of the authors on 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."

The results somewhat surprised the researchers. After crunching the massive volumes of data using a variety of computational models, it became clear that a person's ability to acquire a new language remained strong until approximately 17.4 years of age, almost a decade longer than previously thought.

"It was surprising to us," says Joshua Hartshorne, one of the researchers on the project. "The debate had been over whether it declines from birth, starts declining at five years old, or starts declining starting at puberty."

While a person learning a new language in their teenage years was found to be skilled at picking up the new language, the study did find that a proficiency comparable to a native speaker could only be achieved if the learning began by the age of 10.

"If you want to have native-like knowledge of English grammar you should start by about 10 years old," says Hartshorne. "We don't see very much difference between people who start at birth and people who start at 10, but we start seeing a decline after that."

It's unclear at this stage what occurs around the age of 17 or 18 to reduce a person's ability to pick up a new language. As well a suspected changes in brain plasticity, the researchers hypothesize that a major role could be cultural.

"It's possible that there's a biological change. It's also possible that it's something social or cultural," says Tenenbaum. "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."

All is not lost for those monolingual adults seeking to learn a second language, though. While it certainly is shown that learning a new language later in life is difficult, some research suggests the effort could have major positive effects in the battle against dementia and age-related cognitive decline.

The study was published in the journal Cognition.

Source: MIT News