Is his smile real or simulated?

For years psychologists believed that a real smile was signaled by upturned lips and crinkly eyes. This genuine smile is named after the French physician Duchenne, who passed electrical currents through live subjects and took photos of their weirdly contorted faces.

Researchers suggested that 80% of us are unable to conjure up a fake smile that will trick others because we don't have voluntary control over the muscles around our eyes which signal the Duchenne smile.

Writing in a recent issue of the journal Emotion, Krumhuber and Manstead question whether this 80% estimate is anywhere near the mark. In the first of a series of experiments they found that 83% of the people in their study produce fake smiles that others mistook for the real thing in photographs.

The researchers also explored how people perceived genuine and fake smiles when they saw videos rather than just static pictures. Then it emerged that fake smiles were easier to spot, but the supposedly crucial crinkling around the eyes didn't help much. Instead, telling a real from fake smile relied more on dynamic processes such as how long people hold it, the symmetry of the expression and whether conflicting emotions are communicated by other facial areas.

So the Duchenne smile has taken a bit of bashing in this research, which suggests that most people can fake crinkly eyes. Not only that but the crinkly eyes aren't as crucial for us in judging the sincerity of a smile as other factors. Rather than just the crinkly eyes, it's the whole movement of the face which tells a tale either of deception or of genuine, felt emotion.