Signs and Transitions: Do They Differ Phonetically and Does It Matter?

The point of departure of this article is the cluster of three pre-theoretical presuppositions (P) governing modern research on sign languages: (1) that a stream of signing consists of signs (S) and transitions (T), (2) that only Ss are linguistically relevant units, and (3) that there is a qualitative (e.g., phonetic) difference between Ss and Ts. Of these, the article focuses on the relatively untested P3, which is used to back up P1 and P2, and investigates the velocity and acceleration properties of Ss and Ts on the basis of continuous motion-capture data from Finnish Sign Language. The main finding of the study is that the speed of Ss is slower (and varies less) than that of Ts but that Ss still involve more accelerating (and varying) motion. The purely linguistic interpretation of the results is that the slower speed of Ss enables the addressee to perceive more accurately the fine S-internal linguistic details, manifested by high acceleration. The more theoretical conclusion is that the results support all three Ps but that only P3 is supported directly. As previous key research findings concerning Ts partly contradict P1 and P2, further research on Ts is called for.