An intriguing optical illusion has gone viral, showing a number concealed within a black and grey striped swirl, and it could well give you an interesting insight into the way your eyes work.
The mind-bending puzzle has been shared via Twitter with the question "do you see a number? If so, what number?", and many people have indeed been left baffled after seeing very different figures from their friends.
For example, one person reported seeing the number 45283 while another saw 528 with their glasses on and 45283 without.
A third only saw the number 528 before laying the phone flat, after which point they saw "another 2 or 3".
What do you see?
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The illusion was tweeted by Twitter user @benonwine and has since prompted a range of responses from perplexed puzzle solvers.
One person wrote: "8452839 and I bet the right number has been found. The first digit is the trickiest because it could be a 3, 6, or 8. I'm plumping for the 8".
Another said, "52839, it keeps changing", while a third person insisted, "3452839. It's easy to miss the 3 on the front and the 9 on the back, but they are there".
However, despite many seeing something completely different altogether, the seven-digit figure at the heart of the swirl is actually 3452839.
As reported by the Mail Online, this illusion works by playing on contrast sensitivity, which is understood to be a very important measure of visual function.
Contrast sensitivity allows people to perceive differences between objects and their backgrounds, in ways that prove very useful in everyday life. For example, while driving during foggy conditions.
People with high levels of contrast sensitivity are said to be more likely to be able to see all seven digits of the number straight away.
At the other end of the scale, low levels of contrast sensitivity can be symptomatic of eye conditions such as cataracts or glaucoma.
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