Passage I

Mona Lisa's Elusive Smile

When describing the smile on the face of Mona Lisa, the subject of Leonardo da Vinci's famous sixteenth-century portrait of the same name, many Italians use the word sfumato. (1) The word is appropriate because the portrait often questions its viewers. At first, Mona Lisa seems to be smiling, but moments later the smile disappears—and then reappears. While many artists over the years have come to understand, Leonardo's technique of applying thin glazes to create an airy, luminous effect, no one has yet been able to copy Mona Lisa's mysterious smile.

Recently, a Harvard University neuroscientist Dr. Margaret Livingstone, came up with another possible explanation for Mona Lisa's elusive expression. Her smile appears, fades, and reappears not because her expression is vague, but because the viewers eyes focus on different parts of her face. Dr. Livingstone, whose special interest is how the eye and brain deal with levels of contrast and light, discovered after staring at a photograph of the Mona Lisa in an art book. The subject smiled or didn't smile depending on where Dr. Livingstone's eyes were fixed.

The retina of the human eye uses two distinct regions for seeing the central area of the retina, the fovea, allows people to see details and colors, such as blue and green. (11) The peripheral area allows people to see shadows, motion, and black and white. When viewers are concentrating on Mona Lisa's eyes, and their peripheral vision, which is less accurate than their central vision, picks up shadows that suggest that her mouth is curved and smiling. When the viewer focuses on the mouth, however the shadows disappear, along with the smile.

Despite her scientific explanation for the Mona Lisa's ambiguous quality, Dr. Livingstone continues to view the portrait with total confidence and believes that anyone who tried to reproduce the smile would have to look away from the mouth in order to paint the smile accurately. "How anyone can do that remains a mystery," she said.