Gesturing is often something we poke fun at for being theatrical and distracting. But a study suggests that not only is hand-waving key to being persuasive, but also which hand you use.

The study, published in the June issue of the Journal of Experimental Psychology, shows just that. A team of researchers tested whether subjects were better able to explain metaphors while gesturing with different hands and found that when a right-handed man was gesturing with his left hand — as opposed to his dominant, usual right hand or no hands at all — he scored better in a test that measured how well he could explain a metaphor like “spill the beans.”

This study was conducted by Paraskevi Argyriou, a psychology researcher at the University of Birmingham in England, Christine Mohr, a behavior researcher at the University of Lausanne in Switzerland, and Sotaro Kita, a psychology researcher at the University of Warwick in England.

The researchers say their results suggest that gesturing with one’s left hand — a process controlled by the right hemisphere of the brain — is associated with the same processes involved with explaining a metaphor.

“When the right-hemisphere is more strongly involved in speech production, left hand gestures can more readily support processes in the right hemisphere, such as metaphor explanation,” write the researchers. Explaining a metaphor involves creativity, so the researchers classify it as a right-hemisphere task, sort of like deciding how to talk to your dog.

Since people often gesture while speaking, the two are usually received as a single signal by a listener or viewer. By parsing the effect of gesticulation on speech, these researchers were able to decode a hidden possibility in the communication landscape.

The next time you’re giving a class presentation, arguing on the phone with the cable company, or debating politics with your racist uncle, try gesturing with your left hand for that extra push.

Abstract: Research suggests that speech-accompanying gestures influence cognitive processes, but it is not clear whether the gestural benefit is specific to the gesturing hand. Two experiments tested the “(right/left) hand-specificity” hypothesis for self-oriented functions of gestures: gestures with a particular hand enhance cognitive processes involving the hemisphere contralateral to the gesturing hand. Specifically, we tested whether left-hand gestures enhance metaphor explanation, which involves right-hemispheric processing. In Experiment 1, right-handers explained metaphorical phrases (e.g., “to spill the beans,” beans represent pieces of information). Participants kept the one hand (right, left) still while they were allowed to spontaneously gesture (or not) with their other free hand (left, right). Metaphor explanations were better when participants chose to gesture when their left hand was free than when they did not. An analogous effect of gesturing was not found when their right hand was free. In Experiment 2, different right-handers performed the same metaphor explanation task but, unlike Experiment 1, they were encouraged to gesture with their left or right hand or to not gesture at all. Metaphor explanations were better when participants gestured with their left hand than when they did not gesture, but the right hand gesture condition did not significantly differ from the no-gesture condition. Furthermore, we measured participants’ mouth asymmetry during additional verbal tasks to determine individual differences in the degree of right-hemispheric involvement in speech production. The left-over-right-side mouth dominance, indicating stronger right-hemispheric involvement, positively correlated with the left-over-right- hand gestural benefit on metaphor explanation. These converging findings supported the “hand- specificity” hypothesis.