Let’s start from the very beginning… You surely know that human beings have 5 senses, but 75% of the informations that our brain receive is coming from our sight. The sight come from our EYES, obviously, but also from our brain, which interpret what we see. Visual illusion comes from the differences between our perceptions and expectations and what we really see with our eyes. So, optical illusions make the human visual system into perceiving something that is not present, or into perceiving it wrongly…

Optical Illusions can be divided into three main categories: physical illusions, psychological illusions and cognitive illusions. Physical illusions are like a rainbow, a mirage, etc, but we won’t expand the phenomena here. Psychological illusions is “the effect of the eyes or brain on a prolonged stimulation”  (archimedes’ laboratory). You can see an example on the video above… There, a lots of circles are moving in different directions, and if you relax and watch the video in full screen close to the screen, you will see lines moving even when not looking to the video… I’s a kid of hypnosis. Cognitive illusions cause perception errors, even wen we are aware of the nature of the error. Cognitive illusions are commonly categorized into paradoxial, ambiguous and distorted illusions.

This a very good example of a cognitive illusion




There is quite a lot of illusions existing, so to make you familiar to some of them, I am going to show you some pictures off illusions.

Circles rotating? No, this image is static…

Here a typical type of illusion… that’s amazing isn’t it?

Here again, you think that the picture is rotating, but in fact it’s not…

Again…

For his picture, you really think that the dots go to the center of the picture… The cars accentuate the illusion of 3D…

The ponzo illusion… In fact, the two yellow strips are exactly the same length, but because of the black lines, we  think that on is longer than the other…Illusion again!

this is also a very efficient illusion: You would swear it’s moving! But no, it’s a static picture…

The puzzle of seeing (II) by G. Sarcone

This is also an optical illusion, but it’s clearly different than the others: nothing is moving here. You can discern two things: the scenery, and also a visage.

So, I hope you enjoyed this short introduction to optical illusions, and liked the illusions, both video and pictures. I tried to take the best I could find and selected the most interesting, straightforward informations.