Most people can fake a genuine "Duchenne" smile

For years, the literature on the psychology of smiling has claimed that fake smiles can be easily and reliably distinguished from genuine smiles by the absence of crinkling around the eyes. The eye crinkling of a supposedly real "Duchenne smile" (named after a French physician with a fondness for electrodes) is caused by activation of the orbicularis oculi muscles, which raises the cheeks. The traditional view is that this muscle is not within voluntary control, unlike the zygomatic major muscle that bends the mouth upwards into a smile. Fake smiles therefore feature the upturned mouth but there's something missing in the eyes, or so it was long claimed.

Doubts first emerged in a 2009 paper, in which Duchenne smiles were produced just as often when participants pretended to be amused, as when they were genuinely amused. Now a research team led by Sarah Gunnery has provided more evidence that undermines the old beliefs about Duchenne smiles being a reliable sign of true positive emotion.

Gunnery and her colleagues had 96 student participants (49 men) pull smiling faces into a camera while role-playing genuine positive emotion (e.g. pleasure at a good exam grade) or while role-playing fake positive emotion (e.g. smiling in response to a gift that's not really liked).

Overall, 28 per cent of the smiles were rated by two experienced coders as Duchenne smiles, with the characteristic crinkling around the eyes. This broke down as 31 per cent for positive situations and 24 per cent in the fake positive situations. When naive viewers rated these smiles, they tended to say the Duchenne smiles were more genuine, but this was largely because eye crinkling tended to go hand in hand with more expressive smiling around the mouth.

Next, the participants were presented with a photograph of a person pulling a Duchenne smile and another showing a "fake" smile with no eye crinkling, and their task was to imitate both. Seventy-one per cent successfully imitated the Duchenne smile, and 69 per cent successfully imitated the fake smile.

These results explode the myth that it's not possible to fake a "genuine" Duchenne smile. They also hint at this being a skill that varies from person to person. It was the same participants who tended to display Duchenne smiles in the various conditions of the experiment. Moreover, these Duchenne participants reported feeling that they'd done a good job in the tasks, and they said they were able to pull fake expressions in their daily lives, all of which suggests they have good insight into their facial abilities.

A weakness of the study is its reliance throughout on staged emotion. While the evidence is clear that many people can fake the Duchenne in neutral conditions (albeit while imagining emotional scenarios), we don't know how easy it is for people to do this under conditions in which they truly are experiencing negative emotion. On the other hand, because there were no explicit instructions in the role-playing tasks to pull a Duchenne smile, nor were there any consequential outcomes to provide extra motivation, the prevalence of the ability to fake Duchenne smiles in neutral conditions may actually have been underestimated.

"Findings from the present study strengthen the argument that people can volitionally activate their cheek raiser muscle and put on a Duchenne smile," Gunnery and her team concluded. "Future research will further investigate individual differences, and will use behavioural outcomes to measure similarities in people who deliberately produce the Duchenne smile."

Further reading

Gunnery, S., Hall, J., and Ruben, M. (2012). The Deliberate Duchenne Smile: Individual Differences in Expressive Control Journal of Nonverbal Behavior DOI: 10.1007/s10919-012-0139-4