Hiding a smile in the shadows. I'm Bob Hirshon and this is Science Update.
Leonardo da Vinci's famous painting has inspired romantic songs and art lovers the world over, who become captivated by the Mona Lisa's enigmatic smile.
The portrait also intrigued Margaret Livingstone, a neurobiologist at Harvard Medical School who studies the human visual system. When she looked at the painting a few years ago, Livingstone noticed the Mona Lisa's changing expression.