March 2021

Rotating Snakes Illusion

How to See the Illusion: As you move your eyes around the figure, the “snakes” in the pattern appear to rotate. NOTE: This illusion doesn’t work for everyone!

How the Illusion Works: Essentially, our eyes never stay still. As we scan our environment, we make about 2-3 large eye movements called saccades every second! Even when we think we are fixating on a single location, our eyes are still moving with short, rapid “micro” saccades. The precise pattern of the “snakes” trick our eyes into thinking that they are moving when in reality it is our eyes causing the motion. Why doesn’t this illusion work for everyone? A 2009 study showed that older people perceive less illusory motion than younger subjects, theorizing that preserved illusory motion decreases with age.