Researchers just made a major discovery about hand gestures

In-person conversations have become exceedingly rare due to COVID-19, but for a moment, imagine you’re standing in a crowded bar or club on a Saturday night a few months ago. There are groups of friends scattered all around, and tons of people are telling stories or anecdotes while gesturing with their hands and arms. 

Hand gestures while talking to someone else is a universal human tendency, but for all of modern science’s incredible breakthroughs, we still don’t have any conclusive idea as to why humans move their hands so much while speaking. Now, when two or more people are talking in person, it’s fairly self-explanatory that hand gestures can help emphasize an important part of a story or be used to “explain” a particular idea (“The guy was this tall”). Beyond all that, though, many researchers have also theorized that hand gestures change a person’s speech ever so slightly by adjusting the size of their lungs, chest, and vocal muscles.

A new study from the University of Connecticut put this theory to the test, and sure enough, researchers found that listeners can recognize when someone is gesturing with their hands based on only a recording. Moreover, the listeners were even able to correctly guess the exact motions speakers were making with their hands. A group of volunteers was told to move their favored hand as if they were chopping wood while repeatedly making the “a” sound (as in cinema). While doing that, they were asked to keep the “a” sound as consistent as possible.

Then, those recordings were played back for another group of study participants. The listeners were able to accurately pick out and “hear” when the speaker was moving their arm and hand. Listeners were also asked to move their arms to the rhythm of the speaker’s movements, and they matched their motions perfectly to the recorded speaker’s gestures.

It’s incredibly subtle, and something that no one consciously realizes, but the human body is constructed in such a way that moving one’s hands causes the torso and throat muscles to shift. Consequently, bodily gestures are closely tied to voice amplification and acoustic emphasis. We don’t have any control over this; if you’re moving your hands while speaking, your voice is slightly different. Anyone, if they’re listening close enough, can pick up on these fluctuations, even if the speaker isn’t trying to emphasize anything.

“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 study co-author, UConn psychologist, and director of the Center for the Ecological Study of Perception and Action James Dixon, in a university release.

As we all spend much more time on the phone or awkwardly video chatting through poor internet connections, these findings feel particularly timely. Hand gestures are just as useful now as they were a few months ago.

The full study can be found here, published in Proceedings of the National Academy of Sciences.