The Mystery of Mona Lisa’s Smile

From New Scientist:

If you have been puzzled by Mona Lisa’s smile – how she’s radiant one moment and serious the next instant – then your worries are over. It happens because our eyes are sending mixed signals to the brain about her smile.

Different cells in the retina transmit different categories of information or “channels” to the brain. These channels encode data about an object’s size, clarity, brightness and location in the visual field.

“Sometimes one channel wins over the other, and you see the smile, sometimes others take over and you don’t see the smile,” says Luis Martinez Otero, a neuroscientist at Institute of Neuroscience in Alicante, Spain, who conducted the study along with Diego Alonso Pablos…