Only those with 'sharp vision' can spot the number 8881 in a sea of 8831s

Brainteasers are a brilliant way to keep your mind active and have fun , either on your own or by challenging friends or family. Like any other muscle, the brain responds well to exercises, and brainteasers, crosswords, and sudoku are some of the best ways to test your cognitive abilities.

Different parts of your brain can be challenged , from perception to memory to creative thinking and the sharpness of your vision.

When you add a time limit, many teasers can be very difficult, but, if and when you can complete them successfully, they are very satisfying to finish.

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In this challenge -- which you can see in the image below -- you need to find the number 8881 among a sea of 8831s. Remember, you only have 12 seconds to complete the teaser, which requires your focus to be razor-sharp.

How did you do?

If you couldn't finish it on time, you're not alone. Most people report not being able to complete this difficult brainteaser within the 12-second window.

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While some people's eyes are automatically drawn to the anomaly in the image, most people cannot see it without thoroughly inspecting the image, which is easier said than done with only 12 seconds to do it. If you're still struggling, we provide the answer in the image below, circled in red.