Matthew Hutson in Scientific American:
When we talk, we naturally gesture—we open our palms, we point, we chop the air for emphasis. Such movement may be more than superfluous hand flapping. It helps communicate ideas to listeners and even appears to help speakers think and learn. A growing field of psychological research is exploring the potential of having students or teachers gesture as pupils learn. Studies have shown that people remember material better when they make spontaneous gestures, watch a teacher’s movements or use their hands and arms to imitate the instructor. More recent work suggests that telling learners to move in specific ways can help them learn—even when they are unaware of why they are making the motions.
One study involved people who were asked to swing their arms or to stretch them—both groups were told the motion was to get blood flowing. The researchers found that those who swung their arms were more likely to solve a puzzle that required a specific insight: to connect two strings hanging from the ceiling that were too far apart to reach at the same time, they needed to attach a weight to one to turn it into a pendulum. The blood-flow ruse worked: only three participants suspected a relationship between swinging or stretching their arms and solving the task. Apparently, this type of instructed movement helps thought even without any conscious connection to what a person is doing.