Need I say more?
One of our dogs is deaf. (hearing impaired, if you want – I believe he doesn’t care). He is a shelter dog and actually the one that “listens” best. Because of his lack of hearing, he is very attentive and receptive to hand signs and facial expressions. It’s not actually causing any problems. We do not need to use words.
My son, on the other hand, is sometimes blind to the subtleties of emotions expressed in faces, or doesn’t pick up on the tone of the voice, the words chosen by the person…
He needs more words.