Mind-bending optical illusions (and what they reveal about how our brains work)


You’re not alone if you think the circle on the right looks bigger. Most people do. And as you should have guessed by now, both processes are the same size.

The best Mind bending language optical illusions challenge our perception of reality: what seems true at the time turns out to be false. If we challenge ourselves to think further, we will understand that information, such as visual input, is meaningless. It’s what we do with the knowledge that gives it meaning.

We see by learning to see. Our brains have evolved to identify patterns, creating associations by interacting with the real world. It’s a survival instinct. In renowned neuroscientist Dr. Beau Lotto, “The brain didn’t evolve to see the world as it is… The brain evolved into seeing the world that is useful to see.”

And how does the brain adapt to see usefully? Without delving into vision science theories, such as Bayesian models, a simple truth that defines how we see is that our brain is constantly setting and recalibrating the “norm” in every visual situation.

So when a visual situation deviates from what our brain calls the “norm,” optical illusions result from our brain’s responses to abnormal visual experiences. In other words, our brain will “act” and arrive at seemingly “inappropriate” interpretations.

How do optical illusions work?

Although finding a standard theory to explain all types of illusions would be “a theorist’s dream,” the mainstream academic explanation views the cognitive illusion as “misapplied knowledge used by the brain to interpret or read sensory cues.”

Humans aren’t the only ones who see optical illusions, either. Bumblebees see colors, although their base palette consists of green, blue, and ultraviolet instead of red, green, and blue.

In Dr. Beau Lotto’s experiments with bumblebees, he proves that the bumblebee brain – similar to the human brain – does not encode color information in absolute terms but instead learns through the real world. Bumblebees that survive on blue flowers will go to the gray flower if we construct their environment, so gray is the bluest color in an array of yellow flowers.

These science experiments are a powerful reminder that we “see” the physical world based

on how our brain organizes its elements, such as shapes, sizes, colors, spatial relationships. Now, without further ado, let’s look at some of the best optical illusions we’ve found on the web and what they reveal about the blind spots in our visual perception.

Best optical illusions

  1. Troxler effect

Stare at the center of the blurred image above without blinking. After a few seconds, what do you see? Does the image start to fade?

This visual phenomenon called the Troxler effect, first discovered by Swiss physician Ignaz Paul Vital Troxler in 1804, reveals how our optical system adapts to sensory stimuli. This is because our neurons stop responding to constant stimuli – in this case, the static blurry image in the background – causing the image to disappear from our awareness.

  1. Chubb Illusion (luminance)

The Chubb illusion was first discovered by Charles Chubb and his colleagues Sperling and Solomon in the late 1980s. They experimented with perceived contrast by placing low-contrast visual objects against various backgrounds.

As you can see in the image above, when the textured object is placed on a solid gray background, it seems to have more contrast than when the same thing is set on a high contrast textured background.

One explanation for this standard visual error is “imperfect transmission,” a condition in which the brain must navigate ambiguity for visual perception, such as when viewing something through fog or from a distance. 

When there is a lack of light falling on the retina, our brain tries to determine the actual color or contrast of the object by making an imperfect (and often inaccurate) interpretation, such as when the low contrast object is on a gray background.

  1. Checker Shadow Illusion (contrast)

In this famous visual illusion, the square marked with an A looks much darker than B, doesn’t it? But in reality, they are the same shade of gray. If you don’t believe in me, click this link to see the proof.

Adelson’s checkerboard shadow illusion is a classic example of how our visual system doesn’t perceive in absolute terms. Here, the visual interpretation situation on the checkerboard is complex: there is light hitting the surface, then there is the shadow cast by the cylinder, and light and dark squares under the shadow.

As Adelson explains, there are several variables involved in how the brain determines the colors of squares A and B, using past experiences with contrast and shadows as a point of reference. Here, the proximity of light and dark squares and soft shadows tricks the brain into making poor judgments.

But for Adelson, this illusion is proof of the efficiency of our visual system, rather than its defect, in that it succeeds in constructing meaning by breaking down visual information.

  1. Lilac Chaser (color)

After looking at the cross in the center of this image for about 20 seconds, you will see either a green dot running around the circle or a green dot spinning around it, appearing to erase the magenta dots against the gray background. If you move your eyes, the magenta dots will reappear.

The lilac chaser, otherwise known as the “PAC-man” illusion, is primarily the effect of “negative retinal afterimage,” which occurs when our perceptual system adapts to fill the void left by the “afterimage” of complementary hues on a neutral. Context. In this case, the disappearance of the lilac points produces the appearance of afterimages of the complementary color (green).

And the Gestalt effect contributes to the visual phenomenon of a flying green disc. After a while, the brain begins to integrate the successive afterimages and perceive a single flying object instead. We will go deeper into the Gestalt effect later.

5.Poggendorff’s illusion (geometric)

Look at the image on the left: does the black line appear aligned with the blue line? The black line is aligned with the red, as the image on the right reveals.

Named after Johann Poggendorff, a German physicist who first described this illusion in 1860, the Poggendorff illusion reveals how our brain perceives depths and geometric shapes. Still, the cause of this optical illusion is unknown. It has not yet been sufficiently explained.

Although no theory has satisfactorily explained this visual error, the prevailing belief is that our brain tries to interpret a 2D image with 3D properties and distorts the depth between the lines. If you’re inclined to learn more about it, here’s a comprehensive website devoted to the Poggendorff illusion.


Whether you want to reinforce your message with visuals or illustrate complex ideas with images, understanding the process behind visual perception is crucial to becoming a better visual communicator. Learn more about how to become a better visual thinker here or effectively tell a visual story here.


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