Embarrassed by the crow's feet at the corners of your eyes? Contemplating plastic surgery to remove those unsightly little creases? Think again. Your crow's feet could be your ticket to social acceptance.

Australian researchers have found that we look for the twitch of the crow's feet on the faces of others as a sign of friendliness.

The 19th century French anatomist Duchenne de Boulogne found that the subtle muscle contractions at the sides of the eyes were associated only with authentic smiles. He found that people cannot voluntarily produce the crow's feet creases when they are faking a smile. Thus the authentic smile has been dubbed the ``Duchenne smile".

The University of Sydney's BRAINnet was interested in the question of how important the Duchenne smile was to social communication. It asked 60 people to study the expressions of happy, sad and neutral faces on a computer monitor.

Using an infra-red eye gaze monitoring system, the researchers were able to log where the gaze of the volunteers fell on the pictures. They found the volunteers lingered on the crow's feet just long enough to value the creases as significant to determining whether the subject was genuinely happy.

The head of the university's cognitive neuroscience unit, Dr Lea Williams, said the crow's feet contraction was produced only when people experienced a genuine sense of enjoyment or happiness, suggesting it was evoked only when the brain networks associated with these experiences were activated.

``I would hope that this type of research helps us to put greater value on our facial wrinkles rather than necessarily and only viewing them as the negative signs of age," she said.

Brain imaging evidence suggested we had evolved specialised and hard-wired brain networks to deal with each basic emotion - happy, sad, surprise, fear, disgust and anger - and that there may therefore be an evolutionary basis for these emotions, she said.