Eye Spy: How Optical Illusions Work

By Madhavi Pothukuchi

9 September, 2022

Ever look at an optical illusion and wonder how we can see something that isn’t there? Well, the whole science behind it is quite amusing and still under analysis. Optical illusions are like science’s magic tricks, so let’s find out the secret behind this magic. 

The secret starts with understanding how we perceive things. Our brain is like a supercomputer, processing multiple stuff simultaneously. But our brain’s weakness is it cannot see! The eyes enter here, connected to the brain through the optic nerve and help it see objects around us.

The eyes and the brain communicate using a simple language. The eyes see an object and then, through the optic nerve, tell the brain what the object is. The brain then processes that information and gives us all the required details about the object.

Unfortunately, the eyes don’t always have the proper words to describe what they’re seeing. So, the brain (much like in exams) fills in the blanks that the eyes cannot. It receives partial information about what the eyes are seeing and then guesses the rest to make us understand what we’re seeing. For example, if you can perceive a table at the end of the room, your brain estimates how many feet away it is from you.

Optical illusions are a slight of the eye, literally. They are visuals that confuse the brain because it can’t fully understand what the eyes are looking at. So, when the eyes are telling the brain that the visual it’s seeing is moving, the brain is confused as it also knows that image isn’t supposed to be moving. Thus, an optical illusion is born. 

Scientists are still researching how optical illusions work and what makes our brains perceive something that’s not there. One study showed that our eyes, visual systems and the front part of our brain see the image for what it is – without the illusion part of it. But another part of our brain overrides this reality and compels us to see the illusion. 

One of the most famous and oldest optical illusions is Rubin’s Vase. The picture reveals a white vase over a black background and the profiles of two faces. But even after multiple attempts, it is impossible not to see the faces. What makes the brain push aside the reality of just a vase and still see the faces or vice versa? Unfortunately, a concrete answer hasn't been found.

Some theories suggest that it could be based on what our brains have seen before and hence, fill in the gaps using that information. Another theory suggests that we actually perceive things 100 milliseconds slower than reality. Whatever the reason is, it’s definitely the fun part of science we’d all like to explore more!

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