# 17 Mind-Mangling Optical Illusion GIFs

Don’t believe what your eyes tell you.

## 1. Stare at the black cross and see the blank space transform into a green dot.

Thank you, Troxler effect.

## 2. Move your eyes above this line and the black and white dots will look like they’re rotating clockwise.

But focus on the central red or yellow dots and the outer ones reverse to show their true direction – counter-clockwise.

## 3. Keep looking at the flashing green dot and the yellow ones will disappear.

That’ll be the Troxler effect again. Explanation here.

## 5. Watch dark bands appear as these concentric circles pass over each other

It’s called the Moiré pattern.

## 8. This is a Penrose triangle, also known as the impossible triangle because how does it work?!

Look at any two sides and it appears to be normal, but the third never quite seems right.

## 9. Well, this makes it much clearer…

You can’t actually make a real Penrose triangle in ordinary space.

## Nope, they’re all the same.

This is an example of the Ponzo illusion. Italian psychologist Mario Ponzo suggested that we judge an object’s size based on its background. So if something is the same size as another object but looks “further away” because of the background, we’ll think it’s bigger.

## 12. Which way is this train going?

This is a variation on the classic spinning dancer illusion.

## 13. These yellow and blue blocks look like they’re stepping alternately over the stripes.

But in fact they are always parallel, as you can see when the stripes disappear.

## 14. These blue lines look like they’re moving in pairs.

Until the green squares appear over them, making them a square.

Solution here.

## 16. Look at this black dot and see the outlines filled in with colour.

Thanks, afterimages.

## 17. Finally, watch this for a minute or two, then look away.

But maybe don’t operate any heavy machinery for a while.

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Kelly Oakes is science editor for BuzzFeed and is based in London.

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