Tag Archives: Mona Lisa; art; smile; facial expression; thalamus; optical illusion

Give Me A Smile, Mona Lisa!

To smile or not to smile? Was the “Mona Lisa” actually smiling in the painting that would become one of the most famous works of art? The Mona Lisa smile seems to be the heated debate of artists and surprisingly, scientists all over the world. Take a look for yourself and try to see if you see a smile or not.

The Mona Lisa (left) displayed at Musée du Louvre (right) in Paris

Well for me, I don’t see one when I look closely. This made me wonder why some people saw the smile, while others didn’t. To provide context for anyone who is unfamiliar with the Mona Lisa, it was painted by Leonardo Da Vinci from 1503-06. “Mona Lisa” is thought to be a depiction of Lisa Gherardini, a wife of a cloth merchant (Louvre.fr 2019). However, the rest of the information about the painting comes from the painting itself. Professor Florian Hutzler, a psychologist at the Centre for Neurocognitive Research in Salzburg, explains that Da Vinci used artistic techniques to create an optical illusion to trick the viewers into thinkingMona Lisa was smiling. If viewed face on, the smile appears neutral due to the soft shading of the colors but using your peripheral vision, a subtle smile appears from the merging of the brush strokes (Telegraph 2010). To understand why the Mona Lisa might be playing tricks on us, we must first learn how our brain perceives optical illusions.

A scientific study conducted in Japan examines how our brains are affected by looking at optical illusions. This study had participants perform a shape task, where they judged if 2 optical illusions were the same, and a word task, where they read aloud Japanese letters. While they were doing these tasks, they measured brain activity with an fMRI (Tabei et al. 2015). An fMRI is a tool that measures blood flow in the brain. We should keep in mind a limitation when working with fMRI imaging. fMRI only shows activation of different brain regions measured by blood flow. However, it does not show how the regions connect to each other. Nevertheless, let’s take a look at what the fMRI showed.

Three areas showed activation in the optical illusion task. The thalamus is a relay center that allows you to process the outside world. The inferior frontal gyrus (IFG) and the medial frontal gyrus (MFG) are both involved in resolving conflicting information, such as deciphering optical illusions (Tabei et al. 2015). The conflicting information, when we turn to The Mona Lisa, is whether she is smiling or not. Remember the next time you look at the Mona Lisa or any optical illusion, your brain is doing a lot more work than you think. So now that we know the science behind visual perception of an optical illusion, why is this optical illusion created in the first place?

Areas of the brain activated more in the optical illusion task (above) than without (below)

Some scientists say that the illusion is the result of facial asymmetry. Interestingly, face asymmetry is something Da Vinci himself might have known about and deliberately painted. He had in depth knowledge on facial musculature and movements, found in his notebooks (Adour 1989). In a neuropsychology study done by Marsili et al., this facial asymmetry explanation was studied. The researchers examined whether facial expressions and emotions are influenced by individuals looking at asymmetrical images. A concept that the researchers introduced as past evidence to support the face asymmetry theory is the Duchenne smile. A Duchenne smile simply means it is genuine and can be seen by upper face activation, also known as the wrinkles around your eyes (Ekman et al. 1990) Conversely, a non-Duchenne smile is non-genuine, where no wrinkles around the eyes are present, the next time you see someone smile, you can identify if it’s genuine or not! Looking at the Mona Lisa after learning this, I can see a non-genuine smile, which the researchers say shows facial asymmetry.

A Duchenne/genuine smile (left) vs. Non-Duchenne/non-genuine smile (right)

To further prove facial asymmetry results in the illusory smile, Marsili et al. asked 42 individuals to judge, by a confidence scale (0 none – 10 most confident) and reaction time, which of the six basic emotions was present on 2 chimeric images. A chimeric image takes two left or two right halves and mirrors them next to each other to form a face (see image below). 92.8% of raters indicated that only the left-left image can be used to confidently predict that she was smiling or happy. This led researchers to conclude that facial asymmetry does exist in the Mona Lisa, providing reason behind the illusory smile (Marsili et al. 2019). Additionally, if the researchers explored chimeric images of the eyes or the upper face, this could strengthen the categorization of the smile as non-genuine. However, Marsili et al. (2019) use their findings to imply that the Mona Lisa was not smiling after all, but the truth will remain a mystery.

c-Left-left chimeric image; d- right-right chimeric image

From the enigmatic smile to the ever-growing attraction that pulls visitors from around the world every day, the Mona Lisa will remain a fascinating object of Renaissance art to everyone. The Mona Lisa smile has been the center of scientific studies, the focus of artists and art historians, and the general public. Learning about the science behind the painting and how one painting’s detail can transform the art-viewing experience intrigues me. After my research on the Mona Lisa, I still feel that the debate will continue. While we may never know the true historical and scientific thought behind Leonardo da Vinci’s art piece and if the woman in the Mona Lisa was actually smiling or not, we can definitely say that our brains are hard at work.



K.K. (1989). Adour Mona Lisa syndrome: Solving the enigma of the Gioconda smile. The Annals of Otology Rhinology and Laryngology, 98, pp. 196-199

Marsili, L., Ricciardi, L., & Bologna, M. (2019) Unraveling the asymmetry of Mona Lisa smile Cortex; doi: 10.1016/j.cortex.2019.03.020

Bogodistov, Y., & Dost, F. (2017). Proximity Begins with a Smile, But Which One? Associating Non-duchenne Smiles with Higher Psychological Distance. Frontiers in psychology8, 1374. doi:10.3389/fpsyg.2017.01374

Ekman P., Davidson R. J., Friesen W. V. (1990). The Duchenne smile: emotional expression and brain physiology: II. J. Pers. Soc. Psychol. 58 342–353. 10.1037/0022-3514.58.2.342

Tabei, K., Satoh, M., Kida, H., Kizaki, M., Sakuma, H., Sakuma, H., & Tomimoto, H. (2015). Involvement of the Extrageniculate System in the Perception of Optical Illusions: A Functional Magnetic Resonance Imaging Study. PloS one10(6), e0128750. doi:10.1371/journal.pone.0128750

Spillmann L, Dresp B. (1995). Phenomena of illusory form: can we bridge the gap between levels of explanation? Perception.;24(11):1333–64.

Thibault, M. Levesque, P. Gosselin, U. Hess (2012). The Duchenne marker is not a universal signal of smile authenticity—but it can be learned! Social Psychology, 43 (4), pp. 215-221

“Work Mona Lisa – Portrait of Lisa Gherardini, Wife of Francesco Del Giocondo.” Mona Lisa – Portrait of Lisa Gherardini, Wife of Francesco Del Giocondo | Louvre Museum | Paris, www.louvre.fr/en/oeuvre-notices/mona-lisa-portrait-lisa-gherardini-wife-francesco-del-giocondo.

“Mona Lisa Smile Created Using ‘Trick’.” The Telegraph, Telegraph Media Group, 15 Mar. 2010, www.telegraph.co.uk/culture/art/art-news/7450451/Mona-Lisa-smile-created-using-trick.html.

Image of Mona Lisa from louvre.fr

Image of Musée du Louvre taken by me

Image of fMRI from Tabei et al. 2015

Image of Duchenne smiles from Bogodistov et al. 2017

Last image from Marsili et al. 2019