The different shades as well as the shadows can give the impression that there are figures in movement when in fact that is not the case.
In 2020, researchers at Damon Clark, from Yale University in the United States, identified that the way in which the human brain is deceived by optical illusions it is similar to how such deception occurs in flies.
Specialists evaluated specific types of neurons involved in motion detection in flies and they found a pattern of responses created by the static image. By turning those same neurons on and off, the researchers were able to modify perception. of the flies of that supposed movement, which is a mere optical illusion.
By turning off two types of motion detection neurons, they eliminated the optical illusion altogether. By turning off only one of the two types, the flies recorded the supposed movement in the opposite direction than when both classes of neurons were active.
With this information They concluded that the optical illusion is caused by small imbalances. They then sought to replicate this same experience with humans and were able to prove that the mechanism underlying the perception of the optical illusion in humans works in a similar way to that of flies. Although the human visual system is much more complex than that of these insects, the way optical illusions are produced is based on broadly the same principle.