"Teachers who use gestures as they explain a concept -- such as a hand sweep to emphasize an equation's symmetry -- are more successful at getting their ideas across, and students who spontaneously gesture as they work through new ideas tend to remember them longer than those who do not move their hands."
I have been fascinated in ICT sessions to experience how children share ideas through pointing, changes in body position and how how thoughts and ideas seem to be modelled, externalised or rehearsed through the movement of hands. In classs when words have escape students they act them out by mime when they don't have the vocabulary to express what they want to say but can show. Check out this fascinating Article from the Washington Post. What might the implications of this for understanding the role tools such as Interactive Whiteboards play in learning?