Artist Isia Leviant came up with something called the "Enigma illusion," wherein the purple rings of an image like this seem to contain moving particles. Exploring how this illusion is created, neuroscientist Jorge Otero-Millan helped determine that tiny, involuntary jerks of the watcher’s eye create this false motion in the image. Otero-Millan than created the above homage to the idea: Look into the middle of the pupil to see it.
This is just one of the many fascinating instances where we humans see something that is not there. Instead, we see a false reality that we unconsciously create. I wish I’d reflected on this more fully before pulling the wool over my own eyes. Yes, I bought a human-powered treadmill.
I thought this machine would be superior to walking, hiking, jogging, or cycling. But it wasn’t until I got out on the road with it that I realized it doesn’t come equipped with the proper reflectors or lights. Braking is a problem, and signaling my turns by hand throws off my equilibrium. So why did I buy it? Why?
I blame the tiny, involuntary jerks in my eyes.
Here’s another illusion; both of the ones featured here come from a terrific slide show over at Scientific American. This one is a variation on what’s called the Hajime Ouchi illusion. Move your head back and forward while looking at it. But to get the full effect, paint this on the side of a building and then roll toward and away from it on your human-powered treadmill.
(You may also want to take a peek at Adelson's Checker-Shadow Illusion.)