What are the approaches to studying gestures as a natural communications system?

Two approaches to the study of gestures are: body movement and orientation versus functional analysis. Body movement and orientation would seem the place to start building machine-based recognition systems of natural communication. This approach deals with the location, orientation, and motion of bodies and body parts in 3D space. These are familiar themes in computer vision and related fields. The goals of the body movement and orientation approach are relatively more straightforward and less complex than the other approach to studying gesture, the functional approach, which focuses on the utility and semantics of communications.