• Art lovers and critics have long debated whether or not the Mona Lisa is smiling
  • Scientists at the University of California, San Diego, found that people experience neutral faces differently based on their feelings
  • The new study found that if we subconsciously experience a smiling face we are more likely to remember a neutral one – like the Mona Lisa – as happy .

Scientists have discovered why the Mona Lisa’s expression looks so different to different people and at different times.

For centuries, art lovers and critics have been perplexed by and debated the Leonardo Da Vinci paintings gaze and slight smile – or is it a grimace?

But new research from the University of California, San Diego has shed new light on the luminous and seemingly changing face of the Mona Lisa.

Through experiments on visual perception and neurology, they discovered that our emotions really do alter how we see a neutral face.

People come from all over the world to visit the Louvre and, particularly, to gaze upon Da Vinci’s most famous painting.

Many have remarked on the image’s beauty, the late playwright Sir Noel Coward said she looks ‘as if she has just been sick, or is about to be,’ but for most the fascination in is the uncertainty.

Back in 2005, scientists in Amsterdam in the Netherlands put the Mona Lisa’s face through the paces of its emotion-recognition software.

According to algorithms, her expression is 83 percent happy, nine percent disgusted, six percent fearful and two percent each angry and happy.

But the perception of expressions is a more complex – and, it turns out, constantly changing – calculation in the human mind.

Now science has confirmed what the journalist and biographer Walter Isaacson said about the painting: ‘The Mona Lisa, to me, is the greatest emotional painting ever done. The way the smile flickers makes it a work of both art and science.’