Crossley on Non Speech Communicators:
1. Most people with severe communication impairments know more words than they are able to say.
2. People who know more words than they are able to say may be able to expand their expressive communication by using alternative communication strategies.
3. Many people with communication impairments have hand-function impairments which affect their ability to write or use manual sign or make selections from communication displays.
4. Some people with impaired speech and hand function can use equipment which does not require hand skills (for example, headpointers or scanners controlled with foot switches) to expand their expressive communication. Other people cannot use such equipment, either for practical reasons (you cannot walk and wear a headpointer or use a foot switch) or because of the nature of their neuromotor impairments.
5. People who cannot use other communication strategies may be able to use their hands to access communication aids if their hand-function impairments are remedied either temporarily or permanently.
6. For some people facilitation impairments can provde a temporary remedy for hand-function impairments affecting communication-aid use, and when used as part of a structured teaching program may result in a permanent improvement in hand function.
(from Speechless,
Crossley, 1997, p. 249-250)