In 1989 Newport and Johnson published a study that's been quite controversial, but has really indicated the difference in age of acquisition of a second language, and it's effect on grammatical processing. So in their study, what they wanted to do was to ask people to process a series of sentences and indicate whether they were grammatical or not. Some of these sentences had simple errors, like, I brought some pig to the market. Others had more complex sentences like, the man climbed the ladder up carefully. They split the group up into those who had learned the second langauge before the age of 15, and those who would learn the second language after the age of 17. And they asked a very straight forward question. What was their grammatical score based on the age at which they learned English? What they found was that the early second language learners, and the monolinguals got almost all of them correct. And as they looked at successively older learners of a second language, so these are adults who had learned a second language later in life. Right, later in childhood, or in, into adulthood. That number dropped as they got older. When they looked at the line, and they drew a line across these different groups, they found that between three and seven, the score on this schematical task dropped a little bit every year. And then after seven, it just dropped precipitously. So the idea was that somehow, between three and seven, there was an effect of having had a little bit more exposure to the language, but then after age seven, it just dropped off. Suggesting again that this age seven might be an important cut off for the ability to learn the language in a more native like matter. In this case, they suggested that it might be the closing of a critical period, a point at which grammar can no longer be learned like a native speaker. The studies have been controversial, but then other researchers and who've actually asked the question in a slightly different way. What if we cut them at 20? And they find slightly different results. So there's a lot of discussion of whether there's really this critical period. This age seven at which a window closes. Interpretation by others have sort of softened the view, and suggested well, age matters. Clearly, learning a second language later in life leads to a lower grammatical score. I'm not sure that there's a window that we can identify, but clearly, every age in which a second language is learned, presents with a different outcome in terms of the ability to detect grammatical mistakes. So, taken together these studies looking at grammar, have shown us that age matters. And we have to leave open the question of exactly when this window closes. How it closes, but we've established that age does matter and it does play a roll in grammar
