The relationship of the acquisition of manual signs to severity of aphasia: a training study.

To investigate the relationship between success in the acquisition of signs and the degree of severity of aphasic impairment 12 chronic severely aphasic subjects participated in a training program for the acquisition of a vocabulary of manual signs. The results demonstrate a clear and significant relationship between severity of aphasia and success in the acquisition and generalization of manual signs. The results also indicate that there may be a threshold of severity of aphasia below which acquisition is negligible. Discussion is presented relative to the theoretical, clinical, and methodological implications of these findings.