Don’t Blink: The Science of the Mona Lisa’s Flickering Smile

Don’t Blink: The Science of the Mona Lisa’s Flickering Smile

Arts May 28, 2013 / By Alex Cornacchia
Don’t Blink: The Science of the Mona Lisa’s Flickering Smile

How Leonardo da Vinci combined sfumato and our own eye blinks to animate the Mona Lisa's smile.

Gazing into the eyes of Lisa Gherardini, the famous sitter of Leonardo da Vinci’s Mona Lisa, viewers are often struck with two distinct reactions: one of complete wonder, and one of absolute frustration. It doesn’t take much time to suss out what is causing the latter reaction – the legendary “flickering smile” is enough to make even the most composed Imageamong us want to tear out a couple of hairs while contemplating the eternal (and eternally unanswerable) question of what her enigmatic expression could possibly mean. Is this a smile of joy, of secrecy, of seduction? And perhaps the most unnerving question of all – should her expression even be considered a smile in the first place?

While I cannot hope to provide any satisfactory answers to this larger philosophical query as to the motions of Ms. Gherardini’s mind (really now, what were you expecting from this blog post?), I can ease some of the vexation surrounding this portrait by offering an explanation of a different sort. Even if it is nigh impossible to pin down the thoughts of this mysterious woman, it is entirely possible to figure out why her expression is so difficult to read. The answer, inevitably, lies in Leonardo’s genius as both a painter and a thinker.

The first order of business calls for a good definition of the word sfumato. While the literal translation to English is simply “smoke”, in this context the word actually refers to a painting technique used by Leonardo in which pigments are blended together to create smooth transitions between tones to avoid the use of harsh outlines. In the Mona Lisa, Leonardo’s use of sfumato is most evident around the corners of Lisa’s eyes and mouth. ImageThe result is a more natural rendering of how the human face appears to the naked eye; after all, none of us actually has bold black lines separating our eyes and mouths from the rest of our faces (unless you happen to wear a lot of eyeliner, in which case I offer my sincerest apologies).

Sfumato lends itself not only to creating a more natural representation of color, but also of motion. The technique is what causes us to perceive constant, subtle movements in the expression of Lisa Gherardini – the same movements that you would find in a real human face. So why does the act of blending pigments cause us to perceive something as complex as a flickering smile on the flat surface of a canvas? Diogo Queiros-Conde helps us to unpack the reasoning behind this by applying his theory of entropic skins geometry (or ESG) to the Mona Lisa, demonstrating how the more complex thesfumato is in a painting, the more likely we are to perceive motion.

As Queiros-Conde explains it, it is actually the act of blinking that sets the Mona Lisa into motion. Here’s why: when your eye blinks, it filters less and less light to your retina; with less light going to your retina, your eye sees fewer colors. Blinking involves a continuous series of steps in which your eye filters in less light to the retina, ranging from when your eye is open (full light) to when your eye is closed (no light). At each step of the blinking process, you are seeing a slightly different combination of colors based on how much light is being filtered into your eye. The more variation there is in color when you are viewing an image in full light, the greater the number of images you see as you blink.

Yet this by itself does not explain why people perceive motion in the Mona Lisa. Thinking back to the painting technique of sfumato, you will recall that it involves the blending of an array of different pigments, and that Leonardo primarily used it around the corners of the eyes and the mouth of Lisa Gherardini. The more pigments Leonardo uses for the sfumato, the more colors we see as we look at the painting in full light. Why is her expression so hard to pin down? Because the very act of blinking as you view the painting means you are seeing hundreds of variations of the same image. Every step of light filtration generates a new combination of colors that reaches your eye, but with each blink taking less than half a second to occur, you hardly have time to process what is happening. For just a moment you think you have managed to settle the mystery of her expression, to still the flickering of her smile. Yet at the blink of an eye, it’s already danced away.

But think twice before you engage in an intense staring contest with this famous woman: even if you aren’t blinking as you look at the painting, Leonardo has cleverly erased (using sfumato!) any traces of wrinkles around Lisa’s eyes and mouth that might provide a clue as to her internal state. It is no coincidence that these are the exact locations we look to when we are trying to figure out what emotion someone is feeling. No matter how you look at theMona Lisa, she will always be able to evade concrete interpretation. At least now you know why her smile flickers, and how to hold it still for just a moment – that is, until your next blink. 


Queiros-Conde, Diogo. “The Turbulent Structure of ‘Sfumato’ within ‘Mona Lisa.’” Leonardo 37 (2004): 223-228.

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