Scientists have said that making gestures while talking provide clues to what goes on in our minds.
They have suggested that gestures provide a visual clue to our thoughts and may even change our thoughts by grounding them in action.
University of Chicago psychological scientists Sian Beilock and Susan Goldin-Meadow brought together two lines of research - Beilock's work on how action affects thought and Goldin-Meadow's work on gesture.
And they designed a new study together to look at how gesture affects thought.
The researchers asked the volunteers to solve a problem known as the 'Tower of Hanoi'.
It's a game in which you have to move stacked disks from one peg to another. After they finished, the volunteers were taken into another room and asked to explain how they did it. (This is virtually impossible to explain without using your hands.)
Then the volunteers tried the task again. But there was a trick: For some people, the weight of the disks had secretly changed.
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.
This shows that how you gesture affects how you think.
Goldin-Meadow and Beilock suggested that the volunteers had cemented how to solve the puzzle in their heads by gesturing about it and were thrown off by the invisible change in the game).
In another version of the experiment, published in Perspectives in Psychological Science, the volunteers were not asked to explain their solution; instead, they solved the puzzle a second time before the disk weights were changed.
The people who gestured did worse after the disk weights switched, but the people who moved the disks did not-they did just as well as before.
"Gesture is a special case of action. You might think it would have less effect because it does not have a direct impact on the world," said Goldin-Meadow.
But she and Beilock think it may actually be having a stronger effect, 'because gesturing about an act requires you to represent that act'.
The study is published in Psychological Science.