Thinking with your hands. A link between gesturing and intelligence

When people talk, they often gesture with their hands. Even when their conversational partners cannot see them, people still gesture - when talking on the telephone, for example, or when blind people talk to each other. Young children gesture when they are trying to learn or explain a task or concept.

These hand gestures not only communicate a message to the listener, but also reflect the thoughts of the person who is gesturing. But, while gestures may reflect an individual's thoughts or knowledge, we still don't know exactly why people gesture. Nor do we know why some people gesture more frequently than others.

My colleagues at Germany's Humboldt-Universit?t zu Berlin and Potsdam University and I have discovered differences between people who gesture frequently and those who only gesture rarely. Our study shows that gesturing may be a function of and may even contribute to brain development.

In a recent investigation, we selected fifty-one 11th grade students at three Berlin high schools that specialized in mathematics and natural sciences. The students were given intelligence tests and assigned to one of two groups, according to their scores. They were then asked to solve a visual analogy task in which they had to decide whether two chessboard-like patterns on the left side of a computer screen were mirrored on the same axis as two patterns on the right side of the screen.

Not surprisingly, students with high fluid intelligence - the type of intelligence that is responsible for abilities such as problem-solving, learning, and pattern recognition - performed better at this task than their peers with average fluid intelligence. Even more interesting, however, was that when describing how they solved the problem, the students with high fluid intelligence also gestured more. More specifically, they made gestures with their hands or fingers that simulated circular movements around an axis.

Surprisingly, all the students talked about the same things in their explanations, but almost no one actually mentioned anything about rotating. 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 emphasise 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.

Uta Sassenberg. Humboldt-Universit?t zu Berlin www.atomiumculture.eu