To gesture or not to gesture: what is the question?

Computer synthesized characters are expected to make appropriate face, limb, and body gestures during communicative acts. We focus on non-facial movements and try to elucidate what is intended with the notions of "gesture" and "naturalness". We argue that looking only at the psychological notion of gesture and gesture type is insufficient to capture movement qualities needed by an animated character. Movement observation science, specifically Laban Movement Analysis and its Effort and Shape components with motion phrasing provide essential gesture components (I. Bartenieff and D. Lewis, 1980). We assert that the expression of movement qualities from the Effort dimensions are needed to make a gesture naturally crystallize out of abstract movements. Finally, we point out that nonfacial gestures must involve the rest of the body to appear natural and convincing. A system called EMOTE has been implemented which applies parameterized Effort and Shape qualities to movements and thereby forms improved synthetic gestures.