Optical Illusions

Humans have five senses: olfaction, tact, palate, listening and sight. Each one has its own importance, since they are present in the organs of our body that help us to understand and interact with the world around us.
It’s like a machine. Each sense plays its part and sends its information to the brain, where these information will be interpreted and processed.
The sight, especially, has its importance. “See” is a very important act, but the interesting is that, sometimes, the information that the eyes send to the brain can be not correct. They are called optical illusions, phenomenon that happen when the brain wrongly interpret the information sent to him.
“An optical illusion is characterized by visually perceived images that, at least in common sense terms, are deceptive or misleading. Therefore, the information gathered by the eye is processed by the brain to give, on the face of it, a percept that does not tally with a physical measurement of the stimulus source. A conventional assumption is that there are physiological illusions that occur naturally and cognitive illusions that can be demonstrated by specific visual tricks that say something more basic about how human perceptual systems work.”
Look to the place where a vertical line intercepts a horizontal one. If you stop looking into it, you’ll notice black circles where the lines meet each other. But, if you look to one dot directly, it’ll disappear.

Gear: Pay attention in the dot in the middle of the picture and move your head back and forth.

“Gira-gira”:Look fixedly to one of the black dots in the picture and see what happens with the circles around it.