And here's the key part if you can teach a deaf child asl within the first 5 years, they can learn the language easily and naturally without the need of the grammar rules and how the language works. It just comes naturally but after the age of five, one needs to know how the language works, like now I can watch asl and I can understand asl but to be able to use it just by watching it is hard. I need to know the rules but kids under 5 don't need that. I read this on a research paper on the brain and how language is acquired natively vs secondary or tertiary.