蒙娜丽莎在微笑还是苦笑与人的情绪有关
Scientists have discovered why the Mona Lisa's expression looks so different to different people and at different times.
不同的人在不同的时间观察蒙娜丽莎的表情会得到完全不同的印象，对于这一点，科学家们已经找到其中的原因。
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 Francisco 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.
Dr Erika Siegel and her colleagues study how our emotions change our perceptions of the world around us - even when we aren't aware that something has changed our feelings.
This relies on the modern theory of 'the brain as a predictive organ, instead of a reactive one,' says Dr Siegel.
In other words, 'we have a lifetime of experience and we use those experiences to predict what we are going to experience next. '