Optical illusions reveal secrets of the brain

Night and Day: Escher made over 130 optical illusion drawings during his lifetime.

Do our brains create an alternative reality? Optical illusions are designed to trick our minds, but a group of scientists has proved that the brain could “see things wrong” for a reason.

What’s happening

At first sight, it is a simple picture of birds. But as the eyes adjust, things become clearer. The white birds merge with daylight sky on the left; to the right, the black flock blends to create the night sky. Looking closer, the birds also seem to melt into the patchwork of fields below.

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Optical illusions like Night and Day trick our minds, making us rethink what we see. But new research suggests that the false images we see represent a complex process in the brain.

While our eyes look at objects, it is our brains that develop information into images.

“We’re seeing a story that’s been created for us,” explains a scientist working on the study. Most of the time, the story our brains generate matches the real world – but not always. Our brains fill in gaps using past experiences. When faced with an optical illusion, they make the wrong predictions, and we see the picture differently.

The effect is so powerful that we still see the incorrect image even if we know it is a trick.

Do our brains create an alternative reality?

Some say…

Yes! The ‘stories’ the brain makes up are only based on what our senses report. This means, we only understand a version of what is going on around us. The brain fills gaps based on past experience, changing our understanding of the world. This means we could all be experiencing slightly alternative versions of reality without realising it.

Others think…

Not really. Rather than creating an alternative, our brains expand reality. Our brains know that the senses are slightly slow, so they have developed to make up for any missing information. If they did not create these ‘stories’, we wouldn’t be able to react as quickly. It would make hitting balls, swatting flies, or dodging obstacles impossible.

You Decide

  1. Is it useful to know that we can be wrong?


  1. Follow these instructions for creating your own optical illusion and test everyone else in your home.

Some People Say...

“The brain didn’t evolve to see the way the world is. It evolved to see the world it is useful to see.”

Dr Beau Lotto, neuroscientist

What do you think?

Word Watch

Night and Day
This print was made in 1938 by artist MC Escher. He was one of the first people to experiment with printing optical illusions.
Complicated, or consisting of many individual parts.
The brain guesses how to react to situations based on past experience.


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