Masashi Atarashi, a physics high school teacher from Japan, submitted this wonderful winter illusion to the 2015 Best Illusion of the Year Contest, where it competed as a finalist. Atarashi discovered this effect serendipitously, while watching the snow fall through the venetian window blinds of his school’s faculty lounge—just like his students must sometimes do in the classroom during a lecture!

Notice that as the blinds occupy more area on the screen, the speed of the snowfall seems to accelerate. A great illusion to ponder during our white holiday season.

Nobody knows how Atarashi’s effect works, but our working hypothesis is that each time the snow disappears behind a blind, or reappears below it, it triggers transient increases in the activity of your visual system’s motion-sensitive neurons. Such transient surges in neural activity are perhaps misinterpreted by your brain as faster motion speed.

Happy Holidays from Illusion Chasers!