Can you spot all 12 dots in this mind-bending optical illusion?
An image has surfaced online which is causing people quite a lot of grief.
The latest optical illusion to puzzle the internet isn't quite as straightforward as it seems.
Game developer Will Kerskale tweeted a picture of intersecting grey lines on a white background and asked his followers to spot the 12 blinking dots that appear where the lines meet.
But most people tweeted him messages of frustration because they couldn't see all 12 dots at the same time.
The image was first posted on Facebook on Sunday by Japanese psychology professor Akiyoshi Kitaoka and it has been shared more than 4,600 times so far.
But it originated in a scientific paper published in the journal Perception in 2000.
There really are 12 dots in the image but most people can't see them all at the same time and it's driving them nuts.
In this optical illusion the black dot in the centre of your vision should always appear but, because humans have bad peripheral vision, the dots around the centre ones disappear.
The illusion happens when the brain guesses what's going on in the image as you concentrate on just one part of it.
The journal Perception explains it as:"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."
However, some people have claimed to see all 12 dots in the original image.
One man tweeted: “My wife can see all 12 just fine. Is she a witch? Please advise.”
Another added: “I can see them as well but I’ve had a bottle of wine. Maybe that helps!”