
Ugh some optical illusions come along and ruin your day. Sometimes that's because they're too chilling for words and other times they're too hypnotic. But this one flat out just gave me a headache. Staring at it for too long is NOT advised. You have been warned.
Seemingly made up of overlapping circles (that consist of rectangles), this illusion actually started to distort in front of my eyes, going 3D and adding a little touch of nausea to the aching head. See it below and then find out the surprising secret behind the apparently obvious pattern. It's one of the best optical illusions around, and actually dates back to 2002 – but more on that, and how it works, in a moment.

Ouch, right? But not all is as it seems. This illusion keeps on giving because, as well as the afore mentioned movement, it is is also very different to how it first appears. Look at the circles carefully by following each circle around from the top to the bottom. Do you see it? The shapes don't actually overlap, they are actually just laid out next to each other in an actually very simple way.
See our diagram below for proof:

This illusion – named Pinna's Illusory Intertwining Effect – first appeared in Shifts of Edges and Deformations of Patterns written by Baingio Pinna and Richard L Gregory, an academic journal published in 2002.
The illusion happens because there are too many contradictory messages being sent to our brain at once. The squares form rings but they are slanted, and this wonky element makes us think we are looking at a spiral. The brain then can't work out if the whole thing is made of circles or spirals, and our peripheral vision kicks in to help, and wins out – settling on spirals. The brain then turns the whole thing into a 3D image because that's how it interprets the layered elements when in fact it is flat.
If you're a fan of spinning illusions, see this ballerina – but can you tell which way she is moving?