Every time I think “I will not find a new illusion whit a new explanation” I find a new one even more interesting or weird, after all the site name is “weird opitics”. At first I didn’t notice the way this illusions works like than it hit me.
What to see and what to do?
If you pay a little attention you will see two circles made out of spikes orientated either to the left, either to the right. The key is not the black dot in the middle but it’s related to it. This illusion works better in this shade of grey because it gives the illusion consistence.
In order to make the illusion work you have to focus on the black dot in the middle and to move back and forward from the screen, slowly. You will observe that by doing this, the two circles start to move in different directions considering the movement of our body from the image. Another effect is that the image is getting bigger or smaller depending on the movement.
How does it work?
The two effects that cause this illusion are shape and shading. So if you have the shade but you don’t have the skew the illusion takes place and if you have the skew, but don’t have the shade it also takes place. This illusion is in a way the effect of the shape or shading that trick your mind into thinking that when the shapes move out from the center, they also move in the direction of the shape or shading.