Why Do These Still Images Appear to Move?

Look closely at the image above. Does it seem to rotate?

What you're experiencing is illusory motion, an optical illusion in which a static image appears to move. The effect is the result of interacting color contrasts and shape position.

Scientists aren't sure how our eyes and brain work together to create this appearance of movement, but they have some theories.

One possible explanation is that the color white turns our retinas' receptors "on," while black shuts them "off." Having black and white colors in close proximity or in certain patterns, makes them appear to flicker, which our brain interprets as motion.

Ming-Te Chi, a researcher at National Chengchi University, analyzed numerous self-animating images in 2008 to determine why viewers perceive movement in static images.

Chi and his team found that the arrangement of color bands repeated in small asymmetric patterns could play a role.

Certain combinations of these patterns seem to give the impression of creeping in a particular direction, and the illusion is strengthened if a pattern that seems to flow to the right is placed next to one that seems to flow to the left, such as in "Rotating Snakes" by Akiyoshi Kitaoka (pictured below).

Chi also discovered that specific color combinations make the illusion stronger. He concluded that high-contrast colors are the most effective, such as coupling black and white or blue and yellow.

Take a look at the images below. Do they all seem to move to you?