Is Mona Lisa Smiling or Not? The Eyes Halve It

It was probably Leonardo Da Vinci’s express intent to create an image that would simultaneously enrapture and vex those who would view it. As luck would have it, he possessed artistic talent sufficiently formidable such that here we are, centuries later, not just still asking, but scientifically studying the question of whether or not Mona Lisa smiles.

The answer, it turns out, is simple: yes and no.

The explanation is a bit more complex, but it has everything to do with the different messages that our eyes direct to our brain.

Different retinal cells are involved in receiving varied classifications of information, and translating that into signals sent along to the brain. Any one of these multiple channels of information — light and dark, relative size, relative placement, and so forth — being sent to the brain may temporarily win, and just as quickly lose, the jostling for dominance that takes place among these information channels.

New Scientist presents the most recent scientific study into how the human eye and brain work together in making sense of this most iconic of art works. (As New Scientist reports, a 2000 study suggests that the smile is more evident when the painting is viewed in peripheral vision; a more recent study concluded that whether or not we see the smile is due to random impulses that occur between the retina and the brain.)

Spanish neuroscientists Luis Martinez Otero and Diego Alonso Pablos have found that the perceived size of the painting — a function of distance — plays a big role in whether the face is seen to have any expression at all. The smile was more likely to be seen as the size of the image was increased.

Light and dark — how they are received by our eyes and processed in our brains — is another major player according to the recent findings. Study subjects were more likely to perceive the smile after they had stared at a white screen for 30 seconds than after staring at a black screen for 30 seconds. This test selectively activated those retinal cells that let us see stars at night and those that allow us to discern print on a page, respectively.

The activation of cells that perceive brightness in dark fields — the star-seeing retinal cells — made seeing the Mona Lisa as smiling more likely.

Image courtesy of Cantus, via Wikimedia Commons