"...all the students talked about the same things in their explanations, but almost no one actually mentioned anything about rotation. But by looking at their hands – not by listening to what they were saying – we could distinguish between people with high and average fluid intelligence. We think that these hand gestures mimicked the strategy that the students used in solving the task. That is, they rotated the patterns in their imagination, just as they did with their hands. This suggests that individuals with high fluid intelligence engage more in simulation when imagining the problem than those with average fluid intelligence.
In fact, when we made Magnetic Resonance Imaging scans of the students’ brains, we found that the cortical tissue in several areas of the brain was thicker among those students with high fluid intelligence who gestured more than among those with average fluid intelligence.
Our results indicate that the cortical thickness of those brain regions is related to both high fluid intelligence and the production of gestures. We do not know with certainty yet, but this result suggests that some brain areas may be more developed for the students with high fluid intelligence, possibly like a muscle that grows larger when it is trained.
Recent theories about the processes of thought emphasize the role of so-called action simulation. Evidence from other brain imaging experiments show that some of the same areas of the brain are activated when people only imagine performing an action as when they actually perform it. One theory proposes that these strongly activated simulated actions are manifested as gestures.
We do not know yet whether gesturing facilitates the development of fluid intelligence or whether it is a by-product. But we do know that children who are asked to gesture in certain ways while learning new tasks learn better than children who are asked not to gesture. Considering that gesturing benefits children while learning, it is possible that gesturing plays a role in the development of fluid intelligence, perhaps by simulating action. If this proves to be true, children might be able to literally give themselves a hand in their own development by gesturing more."
It's interesting to think that teaching children to problem solve certain types of problems should involve strategies that take into account that fact that one is trying to train the imagery of the students. Just verbally saying back the steps of a problem or even watching an explanation won't internalize the imagery. To really 'get' certain problems, we have to enter into the simulation and perceive the question and solution in a bodily way.