Researchers decode mystery behind Mona Lisa's smile

The mysterious 'Mona Lisa' has captivated people for centuries, and there has been much discussion about which particular mood the subject is expressing.

A team of researchers with the Institute for Frontier Areas of Psychology and Mental Health, the Medical Center – University of Freiburg, and the Institute of Psychology of the University of Freiburg has determined it's a good one.

See photos of the Mona Lisa:

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The Mona Lisa and the Louvre
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The Mona Lisa and the Louvre
PARIS, FRANCE - FEBRUARY 28: Visitors take pictures of Leonardo da Vinci 'Mona Lisa' inside the Louvre museum on February 28, 2014 in Paris, France. The museum is housed in the Louvre Palace, one of the world's largest museums which opened 1793. (Photo by Christian Marquardt/Getty Images)
Japanese Prime Minister Shinzo Abe (Front) and his wife Akie (3rd R) look at 'La Joconde', a 1503-1506 oil on wood portrait of Mona Lisa by Leonardo Da Vinci, at the Louvre Museum in Paris on May 4, 2014. Japanese Prime Minister Shinzo Abe arrived in France Sunday on the latest leg of a six-nation European tour for trade and security talks at a time of mounting tensions with China. Abe arrived in the French capital on Sunday afternoon and immediately left for a private visit to the Louvre that included stops at the museum's best known works, including the Mona Lisa and Venus de Milo. AFP PHOTO / STEPHANE DE SAKUTIN (Photo credit should read STEPHANE DE SAKUTIN/AFP/Getty Images)
The Louvre is one of the world's largest museums and a historic monument. A central landmark of Paris, where famous sculptures and paintings like Mona Lisa are displayed. (Photo by Jayakumar Radhakrishnan via Getty Images)
Alessandro Vezzosi, the director of the Leonardo da Vinci Museum in Vinci, presents a painting unveiled by the Mona Lisa Foundation on September 27, 2012 in Geneva. The Swiss foundation claims the painting is an earlier version of the 'Mona Lisa' painted by Leonardo da Vinci, although some experts said the claim was unlikely. The Zurich-based Mona Lisa Foundation presented what it described as a 'stunning portrait of Lisa del Giocondo,' along with results from 35 years of research and scientific tests which it claimed proved it was the work of da Vinci and had been completed about 10 years before its famous sister in the Louvre. AFP PHOTO / FABRICE COFFRINI (Photo credit should read FABRICE COFFRINI/AFP/GettyImages)
Picture of a TV screen showing scientific tests made on 'Isleworth Mona Lisa' (L) and the Louvre Museum da Vinci's masterpiece taken during the unveiling by the Mona Lisa Foundation on September 27, 2012 in Geneva of what the foundation claims is an earlier version of the 'Mona Lisa' painted by Leonardo da Vinci, although some experts said the claim was unlikely. The Zurich-based Mona Lisa Foundation presented what it described as a 'stunning portrait of Lisa del Giocondo,' along with results from 35 years of research and scientific tests which it claimed proved it was the work of da Vinci and had been completed about 10 years before its famous sister in the Louvre. AFP PHOTO / FABRICE COFFRINI (Photo credit should read FABRICE COFFRINI/AFP/GettyImages)
Paris, France - February 19, 2014: Beautiful view of the Louvre museum in Paris, France, on February 19, 2014
Paris, France - June 18, 2014: Louvre museum at dusk on June 18, 2014 in Paris. This is one of the most popular tourist destinations in France displayed over 60,000 square meters of exhibition space.
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For their experiments, they altered the mouth area of the original painting, making the corners more upturned or downturned.
They then asked participants to assess whether happiness or sadness was being conveyed in both the edited images and the original.

In all, nine depictions were involved and, in no particular order, shown thirty times.

Dr. Jürgen Kornmeier, one of the scientists, said, "We were very surprised to find out that the original Mona Lisa is almost always seen as being happy."

He told AFP, "We really were astonished. There may be some ambiguity in another aspect...but not ambiguity in the sense of happy versus sad."

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