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




imgres-6“Here is Today” is a wonderful and deceptively simple graphic illustrating this day in time as it relates to the age of the earth, the arrival of insects, and a number of other points of interest along the evolutionary path of the universe. One can only hope that as we are constantly moving towards the use of more technology in classrooms, this is the sort of thing that will emerge as a way to highlight key concepts in science classes. In the meantime, though, have fun clicking your way through time and perhaps learning something new along the way (who knew that the current epoch was named “Holocene?”)

Planting my first post

In which I awkwardly impart the following information:

1. Hi. This is my blog. Welcome! Please, make yourself comfortable. Grab a chair. Fix a drink. Put on some light jazz (if that’s what you’re into). Pet a llama (if that is also what you’re into)*. This is as much your space as it is mine. But this is also not MySpace, so let’s not get confused.

2. This particular blog is going to be about science (don’t stop reading).

3. Yes, I know. Really I do. I know you might be feeling just a bit apprehensive. In fact, you might be feeling a lot apprehensive. After all, it’s SCIENCE (cue “Jaws” theme, or anything else that inspires an equally and inappropriately horrified reaction in you). It’s the thing that sends my friends majoring in the humanities (and, strangely, some fellow psychology majors) running with ears covered, eyes closed, all senses blocked lest a stray molecule of scientific thought creeps in through some secret crevice to confuse them to the point of weeping hysteria.

But I’m not here to send you into a fit of weeping hysteria.

I’m here in pursuit of the “aha!” moment.

I’m here because, in 99% of the cases in which I’m trying to explain a scientific concept to someone, they end up getting it. Not only that, but they’re also really proud of the fact that they get it. And when that happens, they want to explain it to anyone who will listen. Why, you might be curious to know? Spoiler alert: it’s because science is AWESOME.

I love it when people come to realize that science doesn’t have to be difficult. It can be wacky, inspiring, funny, beautiful, terrifying, breathtaking, bold, and sometimes downright strange. And of course, it can be incredibly complex. But here’s some food for thought: you’re incredibly complex, too. That funny object sitting between your ears? It’s what’s allowing you to see all of these symbols and make sense of them as letters, words, sentences, and then finally concepts, thoughts, and ideas – all without you having to put much effort into it. And that’s only the beginning of what your mind is capable of. How’s that for complexity?

So, if you’re game (and I hope you are), let’s set out together in search of the “aha!” moment. Bit by bit, post by post, I’m hoping to make science seem just a little less daunting. And if you already love science? Keep up the excellent work. Go forth and inspire others to love it, too. Fact-check my posts. Perhaps you’ll find some interesting pieces of information here, as well!

I’m just starting out with this science writing thing, so any and all feedback is quite welcome. If you find something confusing or think I may be misinformed on a topic, let me know and I can have some “aha!” moments about my own writing and storytelling. Likewise, if you really enjoy something on here, please tell me! I’d love to know what excites and inspires you, too.

Oh, and the 1% of people who don’t know what I’m talking about when I’m trying to explain some scientific concept? It’s because I wasn’t explaining it well in the first place.

That’s all for today. But check back soon because I’ll be sure to be procrastinating for final exams post more later this week!

Cheers to new ideas,


*Side note: if you are the owner of a llama, I’d very much like to meet you.