Clear Eyes® Eye Care Blog

How Optical Illusions Work

For centuries, people around the world have been fascinated with optical illusions. The notion that your eyes can trick you into seeing something that’s not really there is mind-blowing. And when you dig deeper into the realm of optical illusions and brain games, you’ll discover why your eyes are such brilliant organs.

An accelerated path

Optical illusions work because your brain needs a little rest, so it devised a few shortcuts along the way. Things like colors, shadows and perspectives help the brain understand what it’s seeing, so your brain starts to form an opinion based on these clues.

If the clues are optical illusions designed to induce things like lateral inhibition (Hermann grid illusion), pareidolia (seeing faces in inanimate objects) or Troxler's effect (things in peripheral vision to fade), then your brain ends up fooled and confused.

Playing a brain game

Want to see an example in action? Take a look at the image above. Most people assume it’s a .gif, an animated image. The reality is that this is a static image that isn’t moving at all. While you’re looking at the pattern, the small, rapid movements of your eyes are at fault for making this optical illusion work.

The rapid movement of your eyes is involuntary, so you can’t really blame them. One theory is this movement causes you to “see” the after-image stored in your retina along with the new image. Think of it as a ghost image overlapping a new image. This creates a rippling effect called the moiré effect. When similar patterns are repeated and merged together, it changes your visual perception of the object. That’s why your brain thinks the image is moving.

The good news is if you stare at one spot, the image will stop moving.

Science behind your eyes

Today, neuroscience and optical illusions are tightly woven together because researchers view them as more than entertaining brain games. They use optical illusions to study the human brain, namely how it interprets the information our eyes send to it.

Your eyes take in an enormous amount of information very quickly. In fact, it only takes 13 milliseconds for the human eye to process an image. The brain continues to process subconsciously after “seeing” the image. This means your eyes are constantly trying to figure out what they’re seeing and the brain is constantly telling them what to look at next. Sounds exhausting, right? It is exhausting, even for the king of your central nervous system!

Evolution of optical illusions

Optical illusions and the theories behind them can be traced back to Greek philosophers in the 5th century BC. These innovative thinkers proposed that our sensory organs are capable of deceiving us. It was Plato who surmised optical illusions work because they rely on the senses and the mind.

Fast-forward to the 19th century and you’ll find artists, philosophers, psychologists and scientists around the globe like Johannes Mueller, J.J. Oppel and Hermann von Helmholtz exhaustively researching the phenomenon of optical illusions. Thanks to the famous cartoon of the simultaneously young and old woman sketched by artist W.E. Hill in 1915, Op Art (optical art) was born.

If you focus intently on one spot in that image, can you make it stop moving? Let us know in the comments on our Clear Eyes® Facebook page!