Growing and Shrinking Head – Optical Illusion

Two mind-blowing optical illusions that just might change the size of your head

Science has been known to cause brain growth. The more you learn, the larger your brain. But did you know that you can use the science of optical illusion to change the size of someone’s head, instantly? Don’t worry, the effect isn’t permanent, but it’s a fun illusion to share with your friends!

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Experiment Materials

  • Your eyeballs
  • Our videos

Experiment

1

 

Video #1

Counterclockwise Spinning

Watch the first video above. It is of a black and white spiral spinning counterclockwise. As you watch, stare at the center of the spiral until it disappears.

When the spiral stops, look at the head in the video? What do you notice? Is it shrinking?!

2

 

Video #2

Clockwise Spinning

Watch the second video above. This video is of the black and white spiral spinning in the opposite direction, clockwise. Again, stare at the center of the spiral until it disappears.

When the spiral stops, look at the head in the video? What do you notice? Is it growing?!

How Does It Work

While we typically think of optical illusions as playing tricks on our eyes, the truth is the joke is on our brains! Optical illusions do confuse our eye muscles, but they also confuse information that the brain processes from our eyes. Each of our eyeballs has six muscles attached to it. These muscles make our eyes turn in all different directions. Each of the six muscles works in pairs – one muscle that “pushes” the eyeball and another muscle that “pulls” it back.

When you stare into the center of the spiral, one set of muscles pulls in your eyeballs so that they focus on the spiral and don’t return to their relaxed, center position. While you stare at the spiral, those eye muscles get weak and tired. When you stop looking at the spiral, the overworked muscles relax, and the now stronger, rested, muscles pull your eyeballs past the center position. One of your eyeballs focuses toward the right and one focuses toward the left. This overcompensation causes your brain to process a new image, which results in the growing and shrinking head illusion.

Take It Further

Think it’s just a trick that we did with the video? That’s fair. You can do a lot with technology these days. Watch the videos again. This time, instead of staring at the head that appears after the spiral, pick an item in your room. What happens? That’s right, the same effects happen for any object.