The Ebbinghaus Illusion and Size-Contrast

You’re probably familiar with the concept of the illusion that we’re presenting today. If you haven’t seen a size-perception illusion at the MOI New York, then you’ve almost definitely come across them in school, or somewhere on the internet. The Ebbinghaus Illusion pops up in different forms every now and then, and never fails to blow everyone’s minds. 

The Ebbinghaus Illusion’s play on size and perception makes it a classic. Today, we’re giving you a quick deep dive into the history and the science behind this classic optical illusion.

The Ebbinghaus Illusion used for the Museum of Illusions NYC Blog
The Ebbinghaus Illusion

In looking at the Ebbinghaus Illusion (pictured above), one would most likely assume that the two center dots are different sizes. The orange dot on the left looks significantly smaller than the orange dot on the right, right? You might want to look again.

The orange dots are the exact same size, and it’s actually a failure in our perception that’s causing them to appear different.

The History of Ebbinghaus Illusion

A German psychologist by the name of Hermann Ebbinghaus initially discovered the illusion. Much like Dario Varin and the Neon Color Spreading illusion, the initial discovery wasn’t published in English. Therefore, it went relatively overlooked. When Edward Titchener included the illusion in an English textbook a few years later, the illusion became widely known. Because of this rediscovery, it is also sometimes called the Titchener Illusion.

At the Museum of Illusions NYC, we like to give recognition to everyone who “discovered” any illusion. Honestly, we’re just happy that they were discovered so that we can enjoy them today. 

The Ebbinghaus Illusion is one of many size-contrast illusions that are widely studied by psychologists and cognitive researchers. 

How Ebbinghaus Illusion Works

Called a “size-contrast illusion,” the Ebbinghaus Illusion is one of several of its kind that is incredibly popular and widely studied by scientists. 

The scientific explanation behind the Ebbinghaus Illusion is one that we’ve discussed many times before- a simple perception failure. Because the outer dots on the left side of the image are larger and further away, we perceive the orange dot as being smaller. The outer dots on the right side are smaller and closer, making the orange dot appear larger. 

The philosophical conversation behind the workings of the illusion is a little more interesting. Even when you know that the two orange dots are the exact same size, you likely still perceive them as being different. This has philosophers arguing about what perception means to reality. Are the dots two different sizes simply because we perceive them that way? 

Size-Contrast Illusions Gone Viral

One of the most popular illusions to have surfaced on the internet in the past few years is a great example of a size-contrast illusion. The Jastrow Illusion, pictured below, had a resurgence in 2016 when a father found something perplexing with his son’s toy train tracks. 

The Jastrow Illusion for the MOI NYC blog.
The Jastrow Illusion. The train tracks look like they’re different sizes, right?

When laid next to each other, the tracks appear to be different lengths. However, when placed on top of one another it’s found that they are the exact same size. We have an example of the Jastrow Illusions in our own galleries. As we’ve said before, illusions get discovered and rediscovered many times- sometimes hundreds of years later and by total accident.

To see the Jastrow Illusion, or any of our other size-contrast illusions, in person you’ll have to plan a trip to the Museum of Illusions NYC. Click here to book your tickets!