Aldila, I know that they are not different, I work with deaf children and with other children with special needs, but there are some cases, some people who are poor and doesn't teach their child sign language, I think that than they create some kind of language in their head. 

I have an Indonesian friend who is deaf. She can read and write in Indonesian. She even can read people's lips when they speak Indonesian. 

They're not that diffrerent from us.

Maybe he thinks in images.

They learn a language anyway ¬¬

Reading, Sign Language... to be deaf is not to be stupid.