Optical illusions are fun ways to trick the brain, and this one may be the most effective one yet.
The phenomenon is called a motion aftereffect (MAE) and it causes cells in the brain that are sensitive to a certain direction of movement to get tired, the Daily Mail reports.
It then activates the cells that respond to the opposite direction, making stationary objects appear to move.
In the video below, uploaded by Science Forum, the outer rings spin counterclockwise. A five-point shape features rings that move clockwise, while letters appear in the center. Another spinning circle is around the letters.
IllusionWorks, a company that develops educational illusion-related products, explains:
Your brain represents a sensory quality, such as motion, brightness, color, or depth, not in terms of the firing of one group of neurons, but in terms of the electrical activity of one group of neurons relative to the electrical activity of another group of neurons. For example, the activity of neurons coding for clockwise motion relative to the activity of those coding for counterclockwise motion.
Clockwise motion is signaled by the fact that the neurons coding for clockwise movement fire more strongly than neurons coding for counterclockwise motion. If the clockwise neurons now fire less strongly because their electrochemical batteries run down after several seconds or more of continuous activity, the balance between these two groups is disrupted.
MAE is also known as the “waterfall illusion.”
A scientist, Robert Addams, observed and reported the effect in 1834 while watching a waterfall at Foyers in Scotland. He noticed that the effect can be seen when staring at a waterfall for long enough.