Sign Language Handshapes, Similarly to Speech Sounds, Exploit Biomechanical Endpoints

Abstract

Keywords: sign language, articulation, biomechanicsSpeech motor control approaches have argued that the dimensionality problem can be handled by exploiting endpoints, a type of biomechanical quantal region (Moisik & Gick, 2017, Gick et al. 2020), where a stable output can be obtained regardless of the starting position or variable muscle activation of the articulators (Moisik & Gick, 2013). Endpoints involve a contact between two articulators or an active articulator and a passive articulator. One advantage endpoints offer is in preventing overshoot. In spoken languages, endpoints are maximally exploited in plosive sounds, the most frequent type of consonants occurring in all known spoken languages (Maddieson, 1984: 25). In signed languages, endpoints are exploited in signs where two hands make contact with each other, or where a hand(s) makes contact with the signer’s body (Tkachman, 2022). For example, in signs produced with body contact, variable arm muscle activation does not lead to variable place of articulation (Goyal, Venkata, Tkachman & Gick, 2019). In this study, we extend research on sign-language endpoints by investigating handshape-internal endpoints, which is a state of a finger/joint where it is maximally extended or flexed or where the fingers and/or thumb make a contact with each other and/or the palm. We annotated handshape inventories from five genetically distinct sign languages to determine the extent to which phonemic handshapes in the inventory exploit handshape-internal endpoints. These results support the view that the biomechanical quantal regions previously observed for speech are general to communicative control systems.