The History of Language Theories

The first is called critical period hypothesis. It was proposed by a neurologist named Wilder Penfield along with Lamar Roberts in a 1959 book called speech and brain mechanisms. And this is the idea that there is a critical period in a young person, a young human's life where your brain has the plasticity that's just off the charts and it can learn language then. After that, learning a new language is a lot harder.