In the New York Times, Edinburgh philosopher Andy Clark has a nice essay on embodied cognition. If you're familiar with his book Natural Born Cyborgs, you'll already know the outlines of his argument; but it includes this update:
Most of us gesture (some of us more wildly than others) when we talk... [and it seems that] bodily motions may themselves be playing some kind of active role in our thought process. In experiments where the active use of gesture is inhibited, subjects show decreased performance on various kinds of mental tasks. Now whatever is going on in these cases, the brain is obviously deeply implicated! No one thinks that the physical handwavings are all by themselves the repositories of thoughts or reasoning. But it may be that they are contributing to the thinking and reasoning, perhaps by lessening or otherwise altering the tasks that the brain must perform, and thus helping us to move our own thinking along.
It is noteworthy, for example, that the use of spontaneous gesture increases when we are actively thinking a problem through, rather than simply rehearsing a known solution. There may be more to so-called “handwaving” than meets the eye.
More on this at Contemplative Computing.