Research presented to the British Psychological Society's London conference found that when people look at someone smiling, their focus immediately moves to the areas around the eyes known as "crow's-feet" or "laughter lines" to establish whether the smile is genuine. No lines would indicate a fake smile and lots of lines a true expression of affection and warmth.
Dr Carl Senior, a cognitive psychologist from the Institute of Psychiatry in London, said his findings suggested that evolution has "hardwired" people to look at the crow's-feet as part of their survival instincts. A true smile would indicate a friend whereas a fake one, an enemy. "Someone who is threatening you, whether they are smiling or not, tends to have their eyes wide open and so would not have any lines," he said.
Dr Senior also believes crow's-feet may serve as an important communication tool to indicate social appeasement and willingness to co-operate. Smiling is thought to have evolved as a signal of submission in the face of a threat. "When you smile genuinely your eyes are more closed and so you are less likely to start a fight and more likely to be trying to appease someone," he said.
A genuine smile, is known as the Duchenne smile after the observations of the 19th-century anatomist, Duchenne de Boulogne, who electrified muscles on a patient who had facial paralysis. He established that when people smiled properly the muscles around the eyes contracted.
Many women who have multiple plastic surgery, such as Jocelyn Wildenstein (known as the Bride of Wildenstein for her extensive, and according to her ex-husband "grotesque" plastic surgery), look very doll-like. Whereas those who accept their laughter lines, such as the actor Martin Clunes, may have more appeal.
"If there are areas of the face that people respond to automatically, then taking these areas away by plastic surgery may make people look more fake," Dr Senior said.
Dr Senior conducted eye movement experiments on 63 volunteers who looked for five seconds at pictures of happy, sad and neutral faces. The person's eye movements were monitored using infra-red, corneal-reflection techniques, which recorded where they looked every 50 milliseconds.
The results showed that when someone looked at a picture of a smile, they spent twice as long looking at the corners of the eyes as they did at the mouth, and went back to it several times during the time allocated.
They are more likely to repeatedly return to the "Duchenne" area of the face for pictures of people smiling than for sad or neutral faces. More than a third of the volunteers' eyes returned to the crow's-feet of the happy faces compared with 18 per cent for neutral faces and 13 per cent for sad faces.
"The findings show that humans are showing a hardwired response to the Duchenne marker which may have evolved to distinguish the genuine smile," he said.Reuse content