Optical Illusions - Why Does Our Brain Lie?

Our brains like to play tricks on us, to mislead us into thinking.

Unfortunately, we are all susceptible to them, making us see things differently to the way they really are. Why are we so easily fooled? And above all: how do we get rid of this paradox?


Moving café wall

The lines in the painting appear curved, even though they are in fact perfectly parallel one above the other. They are, after all, formed by the sides of the squares, between which are right angles. Mathematics does not lie! The lines are equal, but our brain tells us otherwise. Why? Well, the colour black absorbs a lot of light and only reflects a small amount. As a result, we think that the black squares occupy a smaller area, hence the illusion of curved lines.

The illusion was first used in a British cafe. On St Michael's Hill in Bristol, England, visitors drinking coffee were given the illusion that the lines were skewing and therefore the whole image was moving. A painting depicting the illusion can also be seen in the exhibition "into the light" at the Center for Science and Senses WOMAI in Krakow.

Herman Grid

Herman Grid
Herman Grid

This is one of the optical illusions resulting from a disturbance in the perception of light. We see grey dots at the intersection of white lines, but they disappear if we keep our eyes on them for a longer time. The illusion is related to so-called peripheral inhibition, which involves the weakening of the action of a certain neuron and the simultaneous stimulation of neighbouring neurons. Information about the field on which the white stripes cross reaches our vision. It is then conducted through a nerve, which, however, is blocked by others responsible for conveying information about the black lines. This is how our brain receives information about the blurred field.

Shape illusions

Although it is hard to believe, the orange circles presented as an optical illusion are the same size.

Illusions of perspective

When all the perspective clues are removed from the image, we have trouble reading the image again. Necker's famous cube changes its position when we look at it. Penrose's infinite staircase can be dangerous, just look at the loop they form.

Author – Małgorzata Lebica

en_GBEnglish (UK)