Take a quick look at the image above. How many dots can you see at once? Did you have to cover up part of the picture to see them all?
Don’t worry you’re not alone! This is an optical illusion designed to use your own brain against you! Or more specifically, how your brain processes information sent from your eyes.
This image was first shared on the internet by psychology professor Akiyoshi Kitaoka after it was originally published in the scientific journal Perception 18 years ago. It has since gone viral with tens of thousands of shares on Facebook, Twitter, and Instagram.
There are twelve black dots at the intersections in this image. Your brain won’t let you see them all at once. pic.twitter.com/ig6P980LOT
— ???????????????? ???????????????????????????????? (@wkerslake) September 11, 2016
There are actually 12 dots spaced at equal intervals across the image above, but the vast majority of people can only see about 5 or 6 at a given time.
“They think, ‘It’s an existential crisis,'” vision scientist Derek Arnold says. “‘How can I ever know what the truth is?'” Understanding how your brain and eyes work together shows that we don’t always perceive what’s right in front of us.
The optical illusion above plays on the same principal as the famous Hermann grid illusion below. In both images, our brains “over-write” reality.
The illusion is made possible by our brain’s attempt to compensate for our relatively poor peripheral vision. Try focusing on just a single word on the page of a large book, then try to read the other words around it without moving your eyes. You’ll notice the other words may seem fuzzy, or maybe jumbled.
In these cases our brains are trying to fill-in the peripheral image based on the observed pattern.
“At a non-intersection, you’ve got a strip of gray line and it’s surrounded by a lot of white,” Arnold explains. “When you get to an intersection, you’ve got multiple gray lines intersecting, and not as much white.”
There’s less contrast at these intersections, meaning there’s more gray than white. The brain assumes this intersection is lighter than the rest of the gray lines, which creates the optical illusion of a light white square. Look at the image above, you’ll notice that if you focus on any one intersection the other intersections around it seem a bit lighter. When you focus on those in turn, they appear darker again.
This illusion makes the black dots completely disappear. Our peripheral vision “can counteract the blurry black dot that is actually, physically there,” Arnold explains.
If you cover up or remove the surrounding patter, all the dots appear together.
What did you think about this illusion? Can you think of any other times your perception may not accurately represent reality?