How the hand has shaped sign languages
In natural languages, biological constraints push toward cross-linguistic homogeneity while linguistic, cultural, and historical processes promote language diversification. I focus in my talk on the effects of these opposing forces on sign languages. Research in movement science has shed light on the nature and effects of neural and motor constraints on hand use. I investigated to what extent the constraints identified in movement science are at play in sign languages, examining the use of the fingers, the two hands, and space in lexical signs. A large corpus of signs from 33 languages was analyzed. In all languages, the hands and fingers exhibited the same form of adaptation to biological constraints found in tasks for which the hand has naturally evolved (e.g., grasping). Our cross-linguistic analyses also showed that signs vary cross-linguistically under the effects of linguistic, cultural, and historical processes. Their effects could thus emerge even without departing from the demands of biological constraints. Cross-linguistic variability consists in changes in the frequencies with which the most faithful configurations to biological constraints appear in individual sign languages. The data I present underscore (a) the key contribution of movement science to the investigation of sign languages, and (b) the usefulness of large cross-linguistic corpora in sign language research.