While you're looking at the pattern, the small, rapid movements of your eyes are at fault for making this optical illusion work. ... When similar patterns are repeated and merged together, it changes your visual perception of the object. That's why your brain thinks the image is moving.

Why do illusions occur?

Illusions occur because of a result of a mismatch between the physical stimuli and their perception by the individual. The mismatch is caused by incorrect interpretation of information received by sensory organs. ... Contrary to this, illusions that vary in different individuals are known as personal illusions.

How does an illusion work?

Optical illusions happen when our brain and eyes try to speak to each other in simple language but the interpretation gets a bit mixed-up. For example, it thinks our eyes told it something is moving but that's not what the eyes meant to say to the brain.