15 optical illusions that will put your mind to the test

Before there was the cinema as we know and enjoy it today, there were many inventions that explored vision and movement. These optical toys were perfected, along with photography, until they generated the perception of movement of an image that, at first, even scared whoever looked at it.

But in addition to disconcerting us, what these optical illusions revealed is the way in which our perception works, since the sense of sight does not only imply what is captured by our eyes, but also what the brain interprets and reworks through from that sensory information.

This was precisely what the “Gestalt Theory” studied, when it held that “The whole is more than the sum of the parts”, that is to say that perception is a significant interpretation of the sensations that come to us from the outside. For this reason, not all of us perceive the same thing, when faced with the same stimuli which, moreover, do not make sense in isolation, but as a whole, as a whole.

To verify this yourself, in this note you will be able to challenge your own mind, or that of your friends, with 15 optical illusions that will make you think that something as everyday as visual perception is not as simple as you imagine.

1. Ripple effect

Can you see a moving ripple effect in this image? This is because the arrangement of the elements in a semicircle, organized in rows, and in contrast to the background, produces that sensation in your brain, even though it is really just a still image.

2. Circles

The same thing happens with these circles that, although they are static, seem to rotate!

3. Spirals

The colors and shades in this photograph give the impression of moving spirals, as the color patterns are similar to the type of information we receive when we see something move. But, if we fix our gaze on one of the circles, we will see that the image is fixed; only together will the illusion of movement arise.

4. Hills

When perceiving the whole of this image, we do not see only lines, but an effect of hills in movement that seem to go up and down.

5. Moving squares

As happens with music, where the silences between the notes are a central part of the piece, in vision the empty spaces can also generate the modification of the total perception of an image, as in this photograph where rectangular lines have been removed in a pattern it produces the sensation of the movement of two squares in the center that seem to jump out of the image.

6. Bicycle

If similar patterns are applied to two circles, and just two lines are added between them, our perception returns us to a bicycle, in motion!

7. Wheel

If you fix your eyes on the center point and move your eyes closer or further away from the photograph, you will see how the drawn wheel appears to rotate, although in fact it does not!

8. Are the lines parallel?

Although in this image the lines are parallel, the arrangement of the black and white squares makes it difficult to perceive the line that separates the rows, making them appear wider at the ends.

9. What is the largest circle?

At first glance, it seems that the orange circle on the left is smaller than the one on the right, but both are the same size, only the surrounding figures generate that perception.

10. Are there gray dots at intersections?

This effect is known as “The Hermann Grid Illusion” because it was observed by the physiologist LudimarHermann in 1870. Looking at this photograph, where a white grid is arranged on a black background, gray spots appear at the intersections, but, when you fixate your gaze, they disappear!

11. Which line is longer?

Although the brackets modify the perception, both lines are exactly the same length. The brain interprets the line with the brackets facing out as being at a point further away compared to the other. That is why it perceives it as longer.

12. Precipice

The effect of shadows and colors generates, in this photograph, the feeling of a precipice where everything falls down.

13. Which table is longer?

Although these tables are the same, we perceive the one on the left as larger because the brain generally interprets vertical lines as longer even though they objectively measure the same. This also influences the sense of perspective.

14. What color are these spirals?

Although it may seem impossible to believe, these spirals that look green and blue are the same color, only the lines that cross them make them look different.

15. Diagonal lines?

The German astrophysicist Johann Karl Friedrich Zöllner discovered in 1860 that although these lines are indeed parallel, they appear to be tilted by the effect of diagonal lines passing through them.

If you liked this note you can also train your lateral thinking with these riddles.