A kinematic study of phonetic reduction in a young sign language

Phonetic reduction arises in the course of typical language production, when language users produce a less clearly articulated form of a word. An important factor that affects phonetic reduction is the predictability of the information conveyed: predictable information is reduced. This can be observed in everyday use of reference in spoken language. Specifically, first mention of a referent is more carefully articulated than subsequent mentions of the same referents, which are often phonetically reduced. Here we ask whether phonetic reduction for predictable information exists in a young sign language, and, in particular, how phonetic reduction is realized in visual languages that exploit various articulators of the body: the hands, the head, and the torso. The only natural languages that we can observe as they emerge in real time are young sign languages, and we focus on one of these in the current study: Israeli Sign Language (ISL). We use 3D motion-capture technology to measure phonetic reduction in signers of ISL by comparing the production of referring expressions synchronically, at different points during a narrative (e.g., Introduction, Reintroduction, Maintenance). Our findings show: (a) that phonetic reduction is present in a young sign language; and specifically (b) that the actions of different articulators involved in discourse are reduced, based on predictability. We consider the importance of these findings in understanding predictability in language more generally.