Can You See All Dots at Once? Your Brain Might Not Let You

 An optical illusion image has gone viral as people try to work out why they can't see all 12 dots at the same time.
 

Japanese psychology professor Akiyoshi Kitaoka posted the image on  Facebook on Sunday morning and within 24 hours it had been shared 7,000  times.
 

Game developer Will Kerslake tweeted the image on Sunday night with the caption: "There are twelve black dots at the intersections in this image. Your brain won't let you see them all at once."
 

By Monday morning he had received more than 27,000 reactions to the tweet.
 

Called Ninio's Extinction Illusion after the French scientist Jacques  Ninio, the image shows a grid of horizontal, vertical and diagonal lines  with 12 black dots at various intersections.
Most people are unable to see all 12 at the same time.
 

So why does this happen?
It is when the eye sees for instance a particularly arranged pattern that the brain may not be able to process accurately.
 

Ninio explains: "When the white disks in a scintillating grid are  reduced in size, and outlined in black, they tend to disappear. One sees  only a few of them at a time, in clusters which move erratically on the  page.
 

"Where they are not seen, the grey alleys seem to be continuous, generating grey crossings that are not actually present.
 

"Some black sparkling can be seen at those crossings where no disk is seen. The illusion also works in reverse contrast."
Twitter user Dan commented: "So its actually your retina that won't let you see them all at once."