Why gesture when no one’s looking?

Just the other day in Seattle I watched a man on his Bluetooth headset waving his hands in the air. People often gesture when they know that they can’t be seen by their listener. Is this just conversational habit? Or is it a sign that gesturing is part of thinking?

Last Thursday afternoon in E1, Table Six was working out the force story of shooting a rubber band off your fingers. Lane asked them to focus in on “the launch act.” He explains: “It's going to start the instant I release the rubber band, okay? And if you like, the instant after I release the rubber band, and it's going to finish when the rubber band is no longer making contact with my finger.”

After some discussion with the group, Sam starts drawing out the forces on the whiteboard. They have drawn two “elastic” opposing forces (in orange) and one blue “thumb force.”



Kerry, however, seems to have some reservations.

Kerry: See what's weird to me about this, this might be getting back to the energy, is that the reason the rubber band mo::oves is not the same as the force, like the force-
Sam: I'm sorry Kerry, I missed that.
Kerry: -that-
Pattie: I know, I have to not think of energy while we're talking about the force
Kerry: (shakes her head) Okay, all right. So I'm not gonna do that.
Pattie: But you can, I think I totally know where you're at
Kerry: Why is the rubber band moving, how does that relate to the net force?

Kerry uses her left hand to stretch out an imaginary rubber band on her thumb. She holds the stretched imaginary rubber band for 16 seconds and through and past her 14 second statement!

Now, here it is in slo-mo (thanks to Benedikt). This is 11 seconds of the gesture extended to 32 seconds. You can tell that no one is looking at Kerry until Pattie turns her head at 00:11 of the original and 00:27 of the slo-mo.



What’s going on here? Kerry is looking up. I would infer that in this moment, she’s aware that no one is looking at her. I think this is an example of a gesture being used to help a speaker think: she is working out the idea that the motion of the rubber band when it is released is not due to the thumb that was initially holding it. If it’s not to illustrate what she’s saying to the group, then why gesture? Is she holding the imaginary rubber band to help her visualize what’s happening? Or help her feel what’s happening? Or both?

And what is Kerry really saying, anyway? She bounces her right hand when she says, “the reason the rubber band moves is not the same as the force.” This is the “thumb force” hand in the whiteboard picture. It seems to me that she is trying to tell the group, hey wait! Maybe the “thumb force” is not part of the “launch act.” It’s something else that makes the rubber band move.

Finally, this moment kind of makes me think of Benedikt’s proximal formative assessment paper. Pattie seems to have not realized that Kerry’s idea is about a specific force (the thumb force) when she says, “I know, I have to not think of energy while we're talking about the force.” Has Pattie inappropriately assessed Kerry’s idea?