Let’s say you are on the phone when a friend, can you tell from the sound of their voice if they are smiling?
In 2008 researchers from the University of Portsmouth in the U.K. set out to determine the answer to this question. To do this they asked subjects 17 questions and had them respond with the phrase “I do in the summertime.” The 17 questions were varied “to provoke reactions such as amusement, mild embarrassment, or just a neutral response.” For example, here are some of the questions to which “I do in the summertime” is the response:
- “Do you ever sunbathe?”
- “Do you eat oatmeal?”
- “Do you ever leave the house without an umbrella?”
- “Do you go skinny-dipping?”
- “Do you go to Mars?”
Each time they responded with “I do in the summertime” the researchers indexed whether the subject was smiling, and what type of smile was being given (Duchenne, non-Duchenne and suppressed). Another set of volunteers listened to recordings of just the “I do in the summertime” response of the subjects and were asked whether they were smiling. The result – the volunteers did a very good job (over 70% accuracy) of distinguishing between a Duchenne smile (the true smile of happiness and enjoyment) and no smile. They were somewhat able to distinguish between suppressed smiles and non-Duchenne smiles. IFOD on the 19 types of smiles, including the Duchenne and suppressed smiles, and the benefits of smiling. Link to research paper.
Another interesting study out of France in 2018 used software to create sentences that mimic both smiling and non-smiling. Thirty-five volunteers listened to the recordings of both the smiling and non-smiling sentences with electrodes on their faces. The researchers found that when listening to smiling sentences the listeners’ facial smile muscles were activated. This study demonstrates that just hearing smiles cause the same empathic smile response that scientists have long known humans do in response to seeing another’s smile (in other words – smiles are contagious – even when heard vs. seen).
These two studies concluded that yes we can hear whether a speaker is smiling. Pretty cool.
We can hear smiles because smiling affects how our voices sound. In fact, one theory why the human smile is usually a positive signal (as opposed to other animals where barring of teeth/fangs is usually threatening) is because of how smiles change the quality of our voices. Here’s a description from the book Fascinate by Sally Hogshead:
In 1980, at the one-hundredth meeting of the Acoustical Society of America, John J. Ohala stunned the audience with his findings. In his paper “The Acoustic Origin of the Smile,” he revealed that the smile didn’t begin as a visual cue, as had always been assumed, but something else entirely . . . . When we smile, we pull the cheek flesh back against our teeth, we make our mouth cavity smaller—and our voice higher, politer, and friendlier. The smile started as a way to sound less threatening and evolved into a way to look more approachable. Not a visual cue, but an aural cue. From a social interaction perspective, then, smiles aren’t window dressing. We’re fascinated with smiles because they communicate friendly intentions and a desire to bond. From an evolutionary perspective, that’s important.