Breaking Down the 3 Types of Optical Illusions

Here at the Museum of Illusions NYC, we love to have a good time. This is exactly why we have built our museum to be a hands-on, interactive experience. Our guests can actually immerse themselves in illusions and experience them firsthand. Just as much as we love to party, we love to educate. Visiting the museum isn’t all about getting a cool Instagram picture, it’s also about understanding the science behind illusions, and learning why our brains process illusions in the way that they do. 

You can break every single optical illusion down into one of three categories- physiological, cognitive, or literal. Let’s take a look at these three categories, and figure out which illusions fall into each of them. We hope that by the end of this, you’ll feel inspired to stop by the museum and categorize some illusions in real life.

Physiological Illusions

When your eyes are exposed to factors such as brightness, tilt, or movement for an extended period of time, this is when physiological illusions occur. Once you look away from the brightness, movement, or tilt, you will still experience it to a degree. Your brain will fill in the gaps of what it thinks should be there. This experience is called “afterimage.”

You’ve probably experienced this many times before without even knowing it! Think about a time that you looked into a bright light for too long. When you looked away, you probably saw the light’s afterimage. It’s the same size and shape of the light, but the opposite color. Physiological illusions take advantage of this afterimage to make it appear as if something is or isn’t there. In order to experience this effect, please don’t start directly into the sun or any bright light source. We have a much better (and safer) example of this occurrence in the image below.

One of the best examples of a physiological illusion is the Hermann Grid. When you’re looking directly at a Hermann Grid, you see a white grid with black squares. If you move your eyes across the pattern, you also see grey spots or smudges where the black lines cross over each other. This is due to the high contrast between black and white, which tricks your brain into seeing the grey spots. 

A Hermann Grid. White lines with black squares. An example of a physiological optical illusions.
The Hermans Grid physiological illusion. Hint: if you can’t see the ghostly grey dots, scan your eyes across the image without focusing on one spot.

Cognitive Illusions

Cognitive illusions depend on an individual’s perception of the world. We love cognitive illusions because everyone sees them differently, and whichever one you see first depends on familiarity. You can break cognitive illusions down even further into four different types- ambiguous, distorting, paradox, and fictional. We’ll dive deeper into those different types in a future blog post, so be sure to keep your eye out for that. 

One of the most notable examples of a cognitive illusion is William Ely Hill’s My Wife and Mother-in-law, which we broke down in a previous post. My Wife and Mother-in-law depicts two different people in one figure- the first is a young woman looking away from the viewer, the second is an old woman in profile, looking down. Which one you see first depends on your individual perception of the image. For this particular illusion, scientists have found that younger people tend to spot the young woman first, while older people find the old woman. They’re both there, but your perception makes all the difference. 

The drawing "My Wife and Mother in Law" which is an optical illusion that shows one figure which can be perceived as either a young woman or an old woman.
The drawing “My Wife and Mother in Law,” originally by William Ely Hill. Who do you see first?


Literal Illusions

Literal illusions are pretty self-explanatory. They are illusions created with the specific purpose of being optical illusions without using any of the cognitive or physiological illusion traits. Often, they are created by combining many smaller images to create a large image. The most well-known literal illusions are found in art. Because they are created intentionally, some don’t consider literal illusions to be illusions at all. But here at the Museum of Illusions, we love all optical illusions equally- intentional or not. 

You can step into pretty much any art museum and find at least one example of a literal illusion hanging in its galleries. Artists such as René Magritte and Octavio Ocampo are famous for using optical illusion in their works. One of our favorite examples of literal illusion is the elephant illusion. It is drawn with the specific purpose of confusing the viewer. Hence, “literal illusion.” Take a look at the image below and tell us how many legs you think the elephant has…

A drawing of an elephant with feet drawn in the gap between the legs. This is an example of a literal optical illusion.
The elephant illusion is the perfect example of a literal illusion. Hint: if it’s giving you a headache, try covering the feet with your hand to see how many legs the elephant actually has.

By drawing the feet in what should be the blank spaces between the elephant’s legs, the artist has created a simple, yet mind-boggling, literal illusion.

Feeling inspired to learn more about the different types of optical illusions? Then you’re our kind of person. Stop by the Museum of Illusions, New York City to meet some fellow illusion enthusiasts and experience physiological, cognitive, and literal illusions in person. Plus, you’ll get some pretty cool Instagram pictures to impress your friends.

Click here to schedule your visit!