Language and brain researchers have been left scratching their heads following a new discovery.

It's been found that starting to learn a language before the age of 10, is the best way to ensure you become fluent.

If you start learning a language after this age, you have no chance of being able to speak like a native.

Boston College Psychology Professor Josh Hartshorne told Mike Hosking this new discovery's thrown a wrench into their theories.

"We had all though that it dropped off a lot earlier, so people were looking at changes in the brain at say five years-old or 12 years-old and nobody was really looking at these later ages so we are really going to have to stat over from scratch trying to figure this out."

LISTEN ABOVE AS JOSH HARTSHORNE SPEAKS WITH MIKE HOSKING