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Test your Brain and Mind with these 9 Classic Optical Illusions

Are the two orange circles of the same size? 

One way to learn more about our brains and minds is to look at how we can trick them–that is, to see how we react to brain teasers and visual illusions.

Quick facts: The brain has two hemispheres, each divided into four lobes. Each lobe is (largely) responsible for different functions. For instance the frontal cortex (in yellow) is responsible for decision making and planning; the temporal lobe (in purple) for language and memory; the parietal lobe (in green) for spatial skills, and the occipital lobe (in red) is entirely devoted to vision: It is thus the place where visual illusions happen..

Below are 9 optical illu­sions that com­bine fun and learn­ing about our visual system. We know you know there is a trick since these are illu­sions… but don’t try to be smarter than your brain; enjoy being surprised!

(You’ll find answers and explanations at the end of the article)

1. Are the squares inside the blue and yellow squares all the same color?

square color illusion test

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2. Are the horizontal lines straight or crooked?

café wall optical illusion

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3. Are the circles static or moving?

circle motion illusion test

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4. How many legs does this elephant have?

elephant visual illusion test

 

5. Are the two orange circles of the same size?

ebbing haus illusion test

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6. Are the two horizontal lines of the same length?

mueller visual games

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7. Do you see gray dots at the intersections of the white lines?

herman grid illusion test

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8. Does Lincoln’s face look normal?

upside down eye illusions test

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9. Where is the baby?

baby illusion test

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ANSWERS AND EXPLANATIONS

Contrast your answers with the ones below, and learn about what was going on in your brain and mind while you experienced each of these classic optical illusions.

 

1. Bezold effect

The smaller squares inside the blue and yellow squares are all the same color. They seem different (magenta and orange) because a color is perceived differently depending on its relation to adjacent colors (here blue or yellow depending on the outer square)..

 

2. Café Wall Illusion

The horizontal lines are straight, even though they do not seem straight.  In this illusion, the vertical zigzag patterns disrupt our horizontal perception.

 

3. Illusory Motion

The circles do appear to be moving even though they are static. This is due to the cognitive effects of interacting color contrasts and shape position.

 

4. How many legs does this elephant have?

Tricky, isn’t it?! This picture isempty triangle illusion test an impossible picture that also contains some subjective contours, such as the Kanizsa Triangle–A white triangle (pointing down) can be seen in this figure even though no triangle is actually drawn. This effect is known as a subjective or illusory contour. The contour of the triangle is created by the shapes around it.

 

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5. The Ebbinghaus Illusion

The two orange circles are exactly the same size,even though the one on the left seems smaller. This size distortion may be caused by the size of the surrounding circles or by their distance to the center circle.

 

6. The Mueller-Lyer Illusion

The two horizontal lines are of the same length, even though the one at the bottom seems longer. As you know, the visual angle gets smaller with distance, so the brain automatically perceives objects at farther distances to be bigger.

In general, lines that have inward flaps, such as corner of a building, are relatively the nearest points of the overall object. Similarly, lines with outward flaps are found at the longer distance, as the farthest corner of a room. So in the Mueller-Lyer illusion, the brain perceives the line with outward flaps to be at a farther point as compared to the line with inward flaps. Consequently, the brain perceives the line with outward flaps to be longer.

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7. Hermann grid illusion

There are not gray dots in this grid. However “ghostlike” gray blobs are perceived at the intersections of the white lines. The gray dots disappear when looking directly at an intersection. This illusion can be explained by a neural process happening in the visual system called lateral inhibition (the capacity of an active neuron to reduce the activity of its neighbors).

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8. Does Lincoln’s face look normal?

It seems normal but now, look at it upright: Lincoln’s eyes do not look quite right!

Some neurons in the brain seem to specialize in processing faces. And faces are usually seen upright. When presented upside down, the brain no longer recognizes a picture of a face as a face but rather as an object — neurons processing objects are different from those processing faces and not as specialized in face recognition. As a consequence, they (we) do not respond to face distortions as well. upside down eye illusions testThis explains why we miss the weird eyes when the face is inverted..

This is how the original image looked like:

 

9. Where is the baby?

Another great example of an illusory contour. The baby’s head is on the left, the baby’s feet are against the trunk of the tree on the right..


–> To keep learning about your brain and mind, check out these Top 25 Brain Teasers, Games and Illusions, for Teens and Adults of Any Age.

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