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 in Germany has determined it’s a good one.

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.
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.”