What are some names for optical illusions

Optical illusions: pictures and puzzles

A great thing, seeing. Light falls into your eyes from outside, the optic nerves inform the brain. That then makes up for everything - and shows an accurate picture of your surroundings. But: is it really that accurate? Sometimes the eyes and the brain make small mistakes - and what you then see are: optical illusions

What do you see in the picture on the right? Just black squares and white lines! But stop. What are those gray dots that flicker at the intersection of the bright bands and immediately disappear when you want to take a closer look at them? Do our eyes screw us up? Right!

Zero points for the retina!

The gray dots are an illusion - and this is due to the way the millions of optic nerves on your retina work: When you look at the picture, each of these nerves picks up a small point of light from it and forwards the information about its brightness to the brain. Because the white bands are surrounded everywhere by the black areas, the optic nerves react particularly strongly to the white light in between - the lines therefore appear particularly bright. Except at the points where they intersect: at these white intersections is the contrast, the opposite between white and black, not that strong. Because up, down, left and right there are white lines everywhere. For an optic nerve that picks up the light from this point of intersection, the white color does not stand out that much.

The result:

The intersections of the white lines do not appear to be quite as white as the other white areas - and therefore flicker gray. The illusion is even stronger in the colored grid image on the left. Here black dots flash on the yellow - and there where you are not looking directly. Why it is like that? Even the inventors of this deception have not yet found an explanation for this.

Hexed figures

At first glance, everything is right. But look carefully. The laws of physics are overridden in these pictures, and the figures look reasonable at first glance. This is because they are composed of perfectly correctly painted parts. Therefore, if you cover part of the figure, everything seems perfectly fine. But if you take your hand away again, it always goes downhill - and that can't be true!

The reason for the confusion is simple:

The individual parts are connected in a way that is not possible in normal life. But you don't see through that at first glance - our spatial vision plays a trick on us! The large drawing by Escher works on the same principle - only that the tricks are even more difficult to see through because of the many beautiful details.

Really weird - or is it?

Bet that the middle stretches of the figures in picture 1 are the same? Never do you say? Then measure again. The fact that the lower section seems longer to us is due to the fact that our brain always "reads" the entire figure when looking at parts of the figure. And since the lower part is longer overall, its middle part also seems longer to us.

It is similar with the illusions in pictures 2 and 3: The lines are completely parallel to each other! The squares and the small lines make us believe that the lines are converging.

Same circles

The inventors of the optical illusion on the left made use of a very simple principle: Figures of the same size appear different sizes - depending on what is shown next to them. So the left black circle is the same size as the right one. That we perceive it as larger is only due to the fact that the red circles around it are smaller than in the second picture. It's pretty easy to poke fun at our brains, isn't it?

Read and experiment at GEOlino.de