Gestures Heard As Well As Seen

A seated man gesturing with both hands while speaking.
Body movements may create changes in our voices that can be heard by others. (Getty Images)

Gesturing with the hands while speaking is a common human behavior, but no one knows why we do it. Now, a group of UConn researchers reports in the May 11 issue of PNAS that gesturing adds emphasis to speech—but not in the way researchers had thought.

Gesturing while speaking, or “talking with your hands,” is common around the world. Many communications researchers believe that gesturing is either done to emphasize important points, or to elucidate specific ideas (think of this as the “drawing in the air” hypothesis). But there are other possibilities. For example, it could be 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 UConn researchers led by former postdoc Wim Pouw (currently at Radboud University in the Netherlands) decided to test whether this idea was true, or just so much hand waving. The team had volunteers move their dominant hand as if they were chopping wood, while continuously saying “a” 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. Gestures are tightly tied to amplitude. Rather than just using your chest muscles to produce air flow for speech, moving your arms while you speak can add acoustic emphasis. And you can hear someone’s motions, even when they’re trying not to let you.

“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,” says UConn psychologist and director of the Center for the Ecological Study of Perception and Action James Dixon, one of the authors of the paper.