Now, this is fascinating and interestingly, the article by the scientist herself is quite entertaining!
Is Mona's Smile just an optical illusion?
Harvard Neurobiologist Margaret Livingstone on Mona Lisa:
A side interest in the lab is to use what we know about vision to understand some of the discoveries artists have made about how we see. The separate processing of color and form information has a parallel in artists' idea that color and luminance play very different roles in art (Livingstone, Vision and Art, Abrams Press, 2002). The elusive quality of the Mona Lisa's smile can be explained by the fact that her smile is almost entirely in low spatial frequencies, and so is seen best by your peripheral vision (Science, 290, 1299) Harvard Medical School Neurobiology Department
These three images show her face filtered to show selectively lowest (left) low (middle) and high (right) spatial frequencies.
