What tricks do illusions play on the mind?

Thanks to the internet, optical illusions again become popular. Maybe there’s some irony about the revived interest in these visual tricks: the most popular illusions rely on people not looking too closely — and not looking too closely is one of the key side effects of internet-based media use.

They are obviously fascinating if you see optical illusions as cool party tricks or examples of the dynamics of human vision and brain development. Below are some classic optical illusions, and the reasons why people are still being fooled to this day.


Glance at the steps above. Find the base… rather, spot the top. Upon closer examination, you’ll realize that there is no beginning or end. There’s no way that’s feasible, right?

According to Erez Freud, a cognitive neuroscientist at York University in Toronto, these familiar steps, called the Penrose stairs, are a type of “impossible object”—a construction that couldn’t exist in reality although its individual pieces look totally valid. The paradoxical dimension takes shape when the brain is attempting to transform a 2D image into a 3D object.

Our noggins assume that lines are always straight from years of trusted experience, and that corners are precisely 90 degrees. But those facts can not be true and still create this eternal staircase of four ways. You can not walk for ever upstairs, particularly in a circle. Two regions in the visual cortex of the brain – the ventral visual pathway and the dorsal visual pathway – usually interact to recognize items and position them in space. For unlikely artifacts such as the stairs above, those two pathways go back and forth more than normal in your gray matter, seeking to come to a conclusion. Yet they can not, which gives rise to an awkward feeling.

The key to this scene is perspective—it works only in 2D. If you saw these steps in real life, and viewed them from any other angle, you’d uncover what you always suspected: a gap between two sections. In other words, a staircase like any other.


The Impossible Trident is an optical illusion which D.H makes. U.S. psychologist Schuster. The idea is based on an advertisement that was used in an aviation journal by Schuster. Indeed the Impossible Trident is an impossible figure, which means it is an object that can not exist.

Looking at it from one end it appears to have two prongs. But if you look over to the other end, the trident appears to have three prongs. It can be very disorientating to look quickly from one end to the other which makes it a really common illusion.


When discovered at the end of the 19th century, this interesting illusion was first known as Kindergarten illusion. It was later rediscovered and re-popularized by the famous British psychologist, Richard Gregory, and called the illusion Café Wall. One day, Gregory was in a café in Bristol on St. Michael’s Hill, where he found this peculiar pattern of wall — thus his new name.

Owing to the spaced rows of contrasting black and white bricks, this illusion makes parallel straight dividing lines look sloped or curved.


The concept of the Fraser Spiral has been discovered and named after psychologist Sir James Fraser. Looking at the visual illusion, it’s easy to believe the black and white lines flow inward. But if you focus on a single line, you will actually notice that each line is actually a complete circle and not a spiral.

The brain is fooled into thinking that this is an endless spiral because of the location of each individual circle and the background colors which contrast with lines.

Hope your eyes didn’t cross!

Check out my related post: Are you a victim of the Moses Illusion?

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