How important are hand images for conveying gestures in virtial design tasks?

Hand gestures are a rich source of information in communication, particularly in communication of spatial concepts which are fundamental to engineering design tasks. However, there are many ways to convey gestures. For example, cursors can be used make simple gestures, so are hand images really necessary, or are simpler approaches sufficient? The work described in this paper is an evaluation comparing collaboration for a spatial design/drawing when users collaborate by three different methods: face-to-face, virtual sketching, and virtual sketching with the hand gestures of the virtual collaborators projected on the drawing surface. We found that users´ performance in the face-to-face collaboration was almost identical to virtual collaboration with hand images. Virtual collaboration without hand images was significantly more difficult. These results suggest that rich hand gestures conveyed with the hands in face-to-face settings are important in joint spatial tasks; their loss reduces effectiveness in virtual collaboration on such tasks, but the addition of hand images projected on a joint work surface can restore effectiveness to levels similar to that of face-to-face collaboration.