10 Optical Illusions That Will Leave You Puzzled


6 min read
Optical Illusion

Check out these ten optical illusions that’ll have you rubbing your eyes and scratching your head in disbelief.

10. Penrose Triangle

Penrose Triangle
Source: Pixabay

Also known as the tribar or impossible triangle, the Penrose triangle was created by Swedish artist Oscar Reutersvärd in 1934 and popularized by Roger Penrose in 1958. So, why is this optical illusion considered an impossible object? Because it plays on our eyes’ interpretation of 2D pictures as 3D objects. In other words, our visual perspective sees a 3D object — or at least the illusion of one — that could not possibly exist. “The problem arises because the viewer assumes that the features of the figure that are touching in the two dimensional representation are at the same distance from the viewer. The use of perspective to create depth adds to the effect of the illusion,” New World Encyclopedia stated on its website.

9. Rubin’s Vase

Rubins Vase
Source: Pixabay

Rubin’s Vase is an all-time classic. There probably isn’t a person alive who hasn’t seen it — at least most people who are old enough to have seen it anyway. Developed around 1915 by Danish psychologist Edgar Rubin, the image shows what appears to be a black vase on a white background. But, upon further examination, you can also see two faces looking at each other. According to ScienceDirect, Rubin’s Vase has been the topic of previous research, but it still remains a mystery as to what psychological determinants and neurophysiological mechanisms come into play when viewing it.

8. Hermann Grid

Grid Illusion
Source: Pixabay

If you’re looking at the above image, then you already know that this optical illusion is all about those little dark dots you’re seeing at the intersections of the white lines. But, where do they come from? It must be magic, right? Nope, it’s our retinas converting visual stimuli into electrical impulses. Allow us to explain. According to the University of Pittsburgh, “posterior neurons convert light stimuli into electrochemical messages that are sent to anterior neurons. The most anterior cells are called ganglion cells. Each ganglion cell receives information from many cells and must decipher what is important and how it will transmit that information. This communication results in unique organization of the ganglion cell known as Center/Surround.” And, it’s this Center/Surround organization that explains why the dark dots appear.

7. Jastrow Illusion

Jastrow
Source: Wikimedia Commons By Ag2gaeh [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
There’s no illusion here. All we see is two toy train tracks of varying sizes, right? Nope, in fact those toy train tracks are actually the same size! First defined by American psychologist Joseph Jastrow more than a century ago, the Jastrow Illusion is an optical illusion involving two objects of equal size, that, when placed parallel to each other, will look as if the object on the bottom is actually much larger than the object above it. Scientists are not sure what causes this phenomenon, but what they have noticed is that similar effects also happen when using other geometric shapes, including lozenges, trapezia, and parallelograms.

6. Peripheral Drift

Peripheral Drift
Source: Wikimedia Commons By Cmglee [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
Did that picture just move? Yes and no. What you are experiencing is a scientific phenomenon known as peripheral drift. While the image itself is completely still, your brain perceives it as a moving image. Why is that? Our brains process high-contrast elements — like black on white, for example — faster than low-contrast elements (e.g. black on gray), leading to a lapse in mental read time, which ultimately causes our brains to perceive motion in still images.

FUN FACT: Peripheral drift only works when our eyes are moving. The moment we maintain a steady stare at a single point, the perceived movement ceases.

5. Fraser Spiral

Fraser Spiral
Source: Wikimedia Commons

Named for British psychologist James Fraser, who published his findings in a 1908 edition of the British Journal of Psychology in an article titled “A New Visual Illusion of Direction,” the Fraser spiral illusion is actually not a spiral at all, hence the name “spiral illusion.” It’s actually a series of concentric circles. And, even though a lot of research has been done on this subject, scientists still have not come up with a viable explanation as to why the human eye sees concentric circles as spirals.

4. Ponzo Illusion

Ponzo
Source: Wikimedia Commons

In the Ponzo illusion shown above, the two yellow lines are identical in size, yet the yellow line at the top looks much larger than the yellow line at the bottom. This is attributed to linear perspective. Since the upper yellow line is farther away, we see it as longer. Another reason why the two lines appear to be different sizes is because of their positioning. Notice that the black lines get closer and closer toward the end. This is known as convergence. It’s these converging lines that give the impression that the upper yellow bar is bigger than the lower yellow bar where the black lines are more separated.

3. Delboeuf Effect

Delboeuf
Source: Wikimedia Commons By Famousdog at English Wikipedia [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)]
First documented in 1865, the Delboeuf effect, named for Belgian philosopher Franz Joseph Delboeuf, is an optical illusion that starts with two dots of equal size. But, when you draw a large circle around one of those dots and/or a small circle around the other dot, one of the dots suddenly looks bigger than the other. Why does this happen? Well, according to an article published by NPR, our brains mislead us by comparing the dots to the surrounding circles.

2. Ames Room

Ames Room
Source: Wikimedia Commons By Andrevruas [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)]
Named for its creator, American ophthalmologist Adelbert Ames, Jr., an Ames room is a distorted room that creates an optical illusion of relative sizes. If you’ve ever seen Willy Wonka and the Chocolate Factory, then you know exactly what an Ames room is. It’s shown in the scene where the group of ticket winners are about to enter the chocolate room, and as Willy Wonka is walking toward the door, he appears to be getting bigger — or the room appears to be getting smaller, depending on your perspective. The reason is because when we view people or objects in an Ames room, there is a loss of normal perspective. So, when a person moves to one corner of the room, they appear to be much larger than a person standing in the opposite corner.

1. Afterimage

Afterimage
Source: Wikipedia

Stare at the above image for at least 5 seconds. Now, look at a blank white object. What you see on the white object is referred to as an afterimage. So, just how and why does this phenomenon occur? Scientific American explains it like this:

We perceive color using cone cells, which are located in the back of our eyes. When we stare at one color for a very long time, the cone cells become fatigued and temporarily do not respond. But, we still can use our other cone cells, however, to see other colors. And, this ladies and gentlemen is how afterimages are formed.

CONCLUSION

Do you have an optical illusion you’d like to share with us and our other readers? Feel free to leave a comment below. Thanks!