Mona Lisa's smile altered by visual noise

SAN FRANCISCO, June 24 (UPI) -- San Francisco scientists have proven visual noise, like snow on an out of tune TV, can alter whether the viewer sees Mona Lisa's smile as happy or sad.

Christopher Tyler and Leonid Kontsevich of the Smith-Kellewell Eye Research Institute experimented with lighting on Leonardo da Vinci's masterpiece, finding that variations could alter people's perception of the famous smile, Britain's Mirror reported Thursday.

Depending on how they were affected by the light, volunteers saw her as happy or sad.

Human sight contains many sources of visual noise, changes in the number of light particles hitting eye cells, Tyler said, adding he thinks the visual noise is what makes people think Mona Lisa's smile is changing.

"That may be part of what makes the painting so powerful," Tyler said.