Gesturing while speaking or "talking with your hands" actually makes the voice louder, University of Connecticut scientists have found.
A new study has suggested that the alterations made to the size and shape of the chest when gesturing affects a person's speech in tone and volume. Although the practice of gesturing whilst speaking has been documented by experts as common human behaviour for thousands of years, the reasons behind humans using their limbs to accentuate verbal communications have remained unclear.
Now scientists say that although this type of body language adds emphasis to speech, it is not in the way researchers first thought. Communication experts believe that gesturing is either done to emphasise important points or to elucidate specific ideas.
But there are other possibilities, which researchers say could show that gesturing, by altering the size and shape of the chest, lungs and vocal muscles, affects the sound of a person's speech.
A team of University of Connecticut researchers in the US led by former postdoctoral researcher Wim Pouw tested this hypothesis.
The team had volunteers move their dominant hand as if they were chopping wood, while continuously saying "ahh" as in "cinema".
They were instructed to keep the "a" sound as steady as they could. Despite that instruction, when the team played audio recordings of this to other people, they found the listener could hear the speaker's gestures. When the listener was asked to move their arms to the rhythm, their movements matched perfectly with those of the original speaker.
Because of the way the human body is constructed, hand movements influence torso and throat muscles and gestures are tightly tied to amplitude. Rather than just using the chest muscles to produce air flow for speech, moving ones arms while speaking can add acoustic emphasis. And a person is able hear someone's motions, even when they're trying to conceal these motions, researchers said.
James Dixon, one of the authors of the paper and UConn psychologist and director of the Center for the Ecological Study of Perception and Action, said: "Some language researchers don't like this idea, because they want language to be all about communicating the contents of your mind, rather than the state of your body.
"But we think that gestures are allowing the acoustic signal to carry additional information about bodily tension and motion. It's information of another kind."
The UConn researchers report was published in Proceedings of the National Academy of Sciences of the United States of America (PNAS).