Part of what makes Leonardo da Vinci’s “Mona Lisa” the most famous painting in the world is the mystery behind her mouth. The confounding feelings the presumed Lisa Gherardini displays in the portrait have been discussed for hundreds of years, and her emotional ambiguity remains a hot point of debate among critics. But if it’s true that art is in the eye of the beholder, then the need for debate is no longer needed: Scientists have determined her expression once and for all.

In a recent paper published in Scientific Reports, researchers from the University of Freiburg explain that their test subjects judged an untouched version of “Mona Lisa” as happy nearly 100 percent of the time. They tested this by showing subjects black-and-white versions of the original painting in random order. Four versions were manipulated to show the mouth curving down, four showed the mouth curved upward, and one was unchanged. When asked to judge the expression on a scale of “sad to happy,” nearly every participant said that the woman in the original painting was smiling in a happy way.

“We were very surprised to find out that the original ‘Mona Lisa’ is almost always seen as being happy,” study co-author Jürgen Kornmeier, Ph.D., said in a statement. “That calls the common opinion among art historians into question.”

Subjects were asked to rate the emotions of these manipulated versions.

In the next part of the study, the researchers attempted to manipulate the perceptual process of judging emotion. They showed subjects the original version (intending for that one to come across as the happiest), three of the sadder versions from the first part of the experiment, and then seven new manipulations. The researchers found that the three sad versions from the first part were judged as even more sad because of the influence of the new images — demonstrating that new information can override earlier perceptions.

“The data shows that our perception, for instance of whether something is sad or happy, is not absolute but adapts to the environment with astonishing speed,” says Kornmeier.

The results of this study, however, should be taken with a grain of salt: Only 12 subjects were evaluated.

And while it’s interesting to conclude that the “Mona Lisa” isn’t as ambiguous as some might presume, it’s the ability to change perceptions that interest the researchers most. Because the brain constantly processes vague information to construct a manageable interpretation of the world, knowing how to manipulate the formation of that construct can be very valuable. Scientists are becoming increasingly aware that perception and physical reality aren’t necessarily one and the same — but cognitive dissonance drives the brain to create a sense of reality that people can live with.

Photos via Scientific Reports, Giphy