Smart Teenage Brains May Get Some Extra Learning Time
npr.org
npr.org
The notion that children learn faster is a myth.
There is no such thing as a "flexible brain".
Children learn faster because they have to, i.e. they can't get a chocolate bar unless they ask for it. Most adults learning a new language have the luxury of being able to use their native language to survive, and tend to default to the easy option if given the chance, especially if they are learning in a country that doesn't use the language they are learning, in which case they can't use it all the time anyway.