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Test subjects almost always rate facial expressions in da Vinci paintings as cheerful / Scientists at the Medical Center - University of Freiburg thus question centuries of assumptions in art history

It is perhaps the most famous painting in the world: the "Mona Lisa" by Leonardo da Vinci. For a long time, one of the main reasons for its enormous appeal was the supposedly ambiguous facial expression of the sitter: happy or sad? Scientists from the Medical Center - University of Freiburg, the Institute of Psychology at the University of Freiburg and the Freiburg Institute for Frontier Areas of Psychology and Psychohygiene (IGPP) have now discovered in a study that test subjects perceive the Mona Lisa as happy in almost 100 percent of cases. They also found that the emotional assessment of the images depends on which other image variants have been shown previously. In their study, the researchers presented the test subjects with the original painting and eight image variants in which the corners of the Mona Lisa's mouth were moved downwards or upwards, resulting in a sadder or happier facial expression. The study was published in the renowned online journal Scientific Reports on March 10, 2017.

"It was a big surprise to us that the original Mona Lisa is almost always perceived as happy. This contradicts the conventional wisdom in art history," says PD Dr. Jürgen Kornmeier, head of the Perception and Cognition research group at the Freiburg IGPP and scientist at the Medical Center - University of Freiburg's Department of Ophthalmology.

Cheerful faces are recognized more quickly

The scientists working with Dr. Kornmeier and co-study leader Prof. Dr. Ludger Tebartz van Elst, Senior Consultant at the Department of Psychiatry and Psychotherapy at the Medical Center - University of Freiburg, initially created eight Mona Lisa variants for the study, which differed only in a gradual change in the curvature of the mouth. The researchers then presented the twelve test subjects with the original and four images each with a sadder and happier facial expression in random order. At the touch of a button, the test subjects indicated for each picture whether they perceived it as happy or sad, and then how confident they were in their answer. The sum of the answers resulted in a percentage value on a scale from sad to happy and a value for the certainty of their decision.

In almost 100 percent of cases, the original and all more positive variants were perceived as happy. The test subjects recognized happy facial expressions more quickly than sad ones. "It seems that we have a filter for positive facial expressions in our brain," says Dr. Kornmeier.

Sad does not always equal sad

In a second experiment, the researchers kept the variant with the lowest mouth curvature as the saddest variant. They then presented the Mona Lisa original as the happiest variant as well as seven intermediate variants, three of which had already been shown in the first experiment. The researchers were astonished to discover that the test subjects now tended to perceive the image variants that had already been shown in the first experiment as more cheerful. "The data show that our perception of whether a face is sad or happy, for example, is not absolute, but adapts surprisingly quickly to the environment," says Dr. Kornmeier.

The study is part of a larger project by Dr. Kornmeier and Prof. Tebartz van Elst at the Medical Center - University of Freiburg, in which perception processes are being researched. "With our senses, we can only take in a very limited amount of information from our environment, for example because an object is partially obscured or poorly lit," explains Dr. Kornmeier. "The brain then has to construct an image of the world that comes closest to reality from the incomplete and often ambiguous information." The Freiburg researchers are investigating how these construction processes take place in healthy people and whether they are altered in people with mental illnesses, such as delusions.

Original title of the study: Mona Lisa is always happy - and only sometimes sad
DOI: 10.1038/srep43511
Link to the study: www.nature.com/articles/srep43511

Contact:
PD Dr. Jürgen Kornmeier
Institute for Frontier Areas of Psychology and Mental Hygiene
Phone: 0761 207-2121 or 0176 61387757
juergen.kornmeier@uni-freiburg.de