Normal human brains typically use speech as dominant mode of communication with acoustic stimulation as dominant sensory input for speech. If brain has damage to auditory system, the 2nd most dominant system for speech will click in (e.g., usually the visual system). Sign language will emerge with all the structural properties of spoken language. (Hauser, Mark D. The Evolution of Communication. Article.)

The use of sign language can stimulate and educate the right brain, thereby cultivating student creativity. Sign language's benefits are that it forces the hearing person to think differently, can add clarity to oral communication, and could be applied to help children with learning disabilities. (ERIC: EJ405300 - Using Sign Language to Access Right Brain Communication: A Tool for Teachers. Abstract.)