Spiral Visual Optical Illusion Aftereffect

This counter-rotating spirals illusion is a “waterfall illusion” and it represents the motion aftereffect that has the ability to allow you to see motion where there is no motion.

What to see?

This question is quite pointless considering the fact that all you can see are a lot of small black and white circles spinning on and on and on. You don’t have to see something in particular, just to pay attention at the motion and the effect will appears soon.

What to do?

To perceive the proper illusion you have to look at the motion of the image. You will notice that you can get an interesting effect just a short time after. Any stationary scene that you’ll lay your eyes on will appear to move in the opposite direction.  The effect may appear even after a few moments of looking at the spinning circles, but for a stronger effect you will have to look for a minute or two. Another important aspect is that you don’t have to move your eyes. But directly look at your target.

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How it works?

Like other aftereffect “illusions”, this one happens due the fact that the visual neurons are getting tired of perceiving the signal motion in just one direction and for them to rest and to recover they tend to balance the motion making the next scene to move in the opposite direction.

For instance: if you looked for a minute or so at a moving image, that represents the waterfall illusion, you may find yourself in the posture to see even stationary objects moving. The human brain tends to perceive movement in all directions, but when he sees movement only in one direction it thinks that something is “wrong” and tries to balance the motions, making them to move in all directions.

Even if the aftereffect makes the scenes look like they’re being distorted they remain the same. Even if the sensation of expansion or contraction exists, the contours remain the same; fact which shows us that the visual system detects and represents motion and position using neurons.

You may wonder why this aftereffect does not appear when we’re in the train, in a car, in a plane or other moving objects. Simple, this effect appears only when just part of your visual system perceives movement and another part is perceiving a static or some other type of movement. For instance at the waterfall only the water moves, the rest remains still; in the train the entire scene moves along with you.

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