In a recent study, volunteers were asked to solve a problem known as the Tower of Hanoi, a game in which you have to move stacked disks from one peg to another. Later, they were asked to explain how they did it (very difficult to do without using your hands.) The volunteers then played the game again. But for some of them, the weight of the disks had secretly reversed, so that the smallest disk was now the heaviest and needed two hands.

People who had used one hand in their gestures when talking about moving the small disk were in trouble when that disk got heavier. They took longer to complete the task than did people who used two hands in their gestures—and the more one-handed gestures they used, the longer they took.

For those who had not been asked to explain their solution (and replayed the game in the interval) were unaffected by the disk weights changing. So even though they had repeated the action with the original weights, they weren’t thrown by the unexpected changes in weights, as those who gestured with one hand were.

The findings add to the evidence that gestures make thought concrete. Related research has indicated that children can come to understand abstract concepts in mathematics and science more readily if they gesture (and perhaps if their teachers gesture).