Gesticulation helps the speaker as well. A recent thesis (unpublished) in my graduate program examined the effect of allowing a lecturer to move around and gesticulate vs. sitting still at a microphone. There were positive effects both in the viewer seeing the movement (not surprising) and, more interestingly, the lecture recorded with movement was better (subjective rating, comprehension) even when the viewer could not see the speaker.
I ran a similar, although not so scientific experiment a few years ago. I tried to pick up girls in clubs with and without gestures when I was talking to them. This was over a one month period. The actual numbers are classified, but gestures won.
