A Mona Lisa Mystery: The Science Behind the Smile

Da Vinci’s Mona Lisa is celebrated for her mysterious smile. At every glance, her countenance seems to change slightly. Upon turning our gaze away from her mouth, we may experience the strange sensation that she is smiling more, as if mocking us. Yet, as soon as we focus our eyes once again upon her mouth, we find she is smiling just as she was before. Is there a method behind this seeming madness? Is it a trick of the light, or a trick of the mind?

Margaret Livingstone (2002), Harvard neuroscientist, suggests that this phenomenon may be because Mona Lisa’s smile is more apparent when seen in coarse resolution. Therefore, in the periphery of our vision, where there are larger receptive fields that are poor in perceiving detail, Mona Lisa appears to be smiling more. When we look directly at Mona Lisa’s mouth, we are able to process detail much more effectively because the receptive fields of cells in our central vision (fovea cells) are much smaller. As a result, Mona Lisa’s smile fades as we focus our gaze to her mouth. In the picture below, note how Mona Lisa's seems to smile more in coarse resolution (as in peripheral vision), and smile less in fine resolution (as in central vision).

From Vision and Art: The Biology of Seeing, by M. Livingstone, 2002, p.73

Another theory for the appeal of Mona Lisa’s smile is that angles of her mouth activate area V5 (the area for processing motion) and the frontal cortex. Neurologist A. Chakravarty (2010), author of "Mona Lisa's smile: a hypotheses based on a new principle of art neuroscience," suggested that Da Vinci “[introduced] an element of implicit dynamism, an imagination of movement of a smiling face, in the painting to increase the aesthetic value of his art work”. According to Chakravarty, Mona Lisa’s smile is appealing because it calls upon one’s imagination of movement. However, Chakravarty’s claim seems quite broad, and does not specify what is it about Mona Lisa’s smile that makes it any different from other subtle smiles that also call upon one’s imagination of motion.

Despite the detailed neuroaesthetics of Mona Lisa’s mouth, we have barely begun to scratch the surface of this great masterpiece. In addition to the enigma of Mona Lisa’s smile, there is still, for example, the enigma of how her eyes seem to follow the viewer and the dynamics of the background. Most importantly, there is the profusion of cultural questions regarding the style of the time period, the identity of Mona Lisa, and Mona Lisa’s relationship to Da Vinci . These questions are important aspects of art that neuroaesthetics could never encompass to address.