It was created more than 100 years ago, but this image of a duck and a rabbit is sparking a huge response on social media.
Depending on what you see and how quickly you register the two images is said to be an indication of how creative you are.
The drawing first appeared in a German magazine in 1892 and was first used by American psychologist Joseph Jastrow, who used the sketch to make the point that perception is not only what you see but is also telling of brain activity.
Jastrow's research and other subsequent studies were based on how fast a person can make out two animals and how quickly participants could change their perception between the duck and the rabbit.