The Mona Lisa smile - a trick of the light

By STEVE CONNOR

The mystery of the enigmatic smile on the Mona Lisa has been solved by a scientist, who proposes that it has more to do with a trick of the eye than the brush skills of her creator.

The face of the world's most famous portrait has been analysed for its visual content and found to possess a hidden smile that can be seen only when not looking directly at Mona Lisa's mouth.

It could explain why generations have waxed lyrical about an elusive smile that may not have been intended when Leonardo da Vinci painted her in about 1502. Margaret Livingstone, a neurobiologist at Harvard Medical School, analysed the painting using light filters that can distinguish between low and high spatial frequencies, which determine how blurred an image is.

High spatial frequencies occur at the edges of an object, such as the outline of a cheekbone, whereas between two edges - for instance, between the sides of a face - there are far lower spatial frequencies.

Dr Livingstone found that when the painting is analysed for low spatial frequencies, the smile is pronounced. At higher spatial frequencies the smile almost disappears.

"If you look at the painting so that your gaze falls on the background or on Mona Lisa's hands, your perception of her mouth would be dominated by low spatial frequencies, so it would appear much more cheerful than when you look directly at her mouth," she said.

Dr Livingstone describes the preliminary results of her research in the journal Science.