If Mona Lisa doesn’t look happy to you, that might be because of your own mental state, according to scientists at the University of California, San Francisco.

Our emotions change our perceptions of the world around us, they say, and that includes works of art. “If you see the Mona Lisa after you have just had a screaming fight with your husband, you’re going to see [the painting] differently,” Erika Siegel, one of the researchers, told the Daily Mail. “But if you’re having the time of your life at the Louvre, you’re going to see the enigmatic smile.”

The study is based on the theory that the brain is a predictive organ that looks to past experiences to know what to expect from the future. In Siegel’s experiment, she showed 43 participants a series of faces, with two different images appearing before each eye. Everyone has a dominant eye, so faces shown to the non-dominant eye only register subconsciously.

While the dominant eye was shown a face with a neutral expression, the non-dominant eye was presented with a variety of happy, angry, and neutral faces. Siegel likens this subconscious intake of emotional imagery to the effect our own emotional state has on our perceptions. Sure enough, when asked afterwards to sort through all of the faces and identify which ones they had seen, the subjects were more likely to think the neutral faces were happy when they had also seen a smiling face with their non-dominant eye.

Apprentice of Leonardo da Vinci, Mona Lisa (ca. 1503–16). Courtesy of the
Museo del Prado.

These findings are the latest in a large field of research into the Mona Lisa‘s enigmatic expression over the years. In 2005, Dutch researchers used emotion recognition software and computer algorithms to find that the Mona Lisa‘s smile was precisely 83 percent happy, nine percent disgusted, six percent fearful, two percent each angry and happy, and less than one person neutral.

A 2017 study with human subjects reaffirmed these findings, with 97 percent of subjects judging the Mona Lisa to be happy.

In 2015, British academics dubbed Leonardo DaVinci‘s creation “the uncatchable smile,” and claimed the expression’s subtlety was intentional, designed by the artist to be visible only from certain angles.

There’s also a theory that the Mona Lisa is smiling because she has syphilis.

Meanwhile, a new study reported in Milenio found that a second copy of the painting at the Prado, may have been painted by the Spanish artist Fernando Yáñez de la Almedina, based on the discovery of hidden Spanish symbols, such as the face of a Moor and Catalan-style architecture, in the background.