In the absence of any clues, most of the people in this office interpreted this optical illusion as simply an abstract black and white scrawl.
Some saw a lobster, while others saw a nose-diving crow.
Facebook user Savannah Root posted the image to her page, confessing: “I stared at this picture for an hour trying to figure out what it was.
“Once you figure out what it was and comment below, please don’t ruin it for anyone… And please don’t comment on this post what it is… Let’s see if it takes you all hours like it did me until I had Josh show me.”
The intriguing image has been shared more than 5,000 times in under a week and has been liked by a whopping 31,000 users.
Carol Sternberg commented: “It took me a few minutes. Once you see it, you can’t un-see it. Very frustrating until you get it.”
[If you've come this far it's time for the big reveal: It's a cowboy.]
But why is it that some of us can see these images and some of us can’t?
Research from the University College of London suggests the way you react to an optical illusion depends on the size of your visual cortex – which can also determine how introspective you are.
Dr D Samuel Schwarzkopf explains: "Our work is the first to show that the size of part of a person's brain can predict how they perceive their visual environment."
Meanwhile Mental Floss writes: “Most Magic Eye[3D images which purport to hide a 'hidden' visual] problems have to do with the way the eyes work with each other and the brain. To view 3D stereo images, your peepers have to work together as a coordinated team. If they're not pulling together, you're going to have some glitches in your binocular (two-eyed) vision or stereo vision (where the two slightly different views from your eyes are combined in the brain).
"A number of things can cause binocular and stereo vision impairment — most commonly, deviations or misalignments of one or both eyes ("crossed eyes" or "wall eyes"), situations where one eye is dominant because visual stimulation either transmits poorly or not at all from the other, astigmatism or cataracts. If you think you have an eye problem, go see an eye doctor who can test and treat your stereo vision.”