I know what you're thinking: There's a contest every year for the best illusion? The answer is yes, and after you see this year's winner, you're going to check out all the finalists too because these illusions will blow your mind.
We can all thank the Neural Correlate Society (NCS) for year after year of great optical illusions, and this year has been no different. The society basically wants to popularize the knowledge of all the funky things are brain does to process sensory information and so holds the Best Illusion of the Year contest.
NCS describes its purpose on its about page, explaining,
We are committed to promoting public knowledge and medical translation of new discoveries related to the neural correlates of sensory and cognitive experience. That includes highlighting discoveries made by the world's under-represented groups, and disseminating information worldwide on new perceptual and cognitive discoveries. We host a variety of annual events that highlight important new discoveries to the public, including the Best Illusion of the YearSM Contest.
Anyway, let's talk about the winning illusion for this year's contest. This thing literally hurts my brain, like, I can feel my brain pulsating in confusion as it quietly says "WTF" to itself under its breath.
This illusion probably should've just asked my brain to do a back flip because that would be easier than asking my brain to actually process what's happening in this video. That's how mind-boggling this illusion is.
The video basically provides the hints for you as it goes along, but to briefly contextualize the video, nothing in it is moving. Your brain is going to think things are moving, but things aren't actually moving at all.
This illusion was apparently spun up by Mathew T. Harrison and Gideon P. Caplovitz from the University of Nevada, Reno. The NCS website explains exactly what's going on, saying,
Previous illusions have demonstrated that drifting Gabors that translate across the visual field can appear to move in the wrong direction (i.e. in a direction that is different than the actual translation). Here we show that configurations of drifting Gabors that are stationary can give rise to dramatic global motion percepts: a rotating square, oscillating chopsticks and rolling waves. Although the Gabors themselves are not changing position, the drifting motion within them causes the illusion that the entire configuration is moving!
Try pausing the video to capture the Gabors, the little drifting/rotating things, moving around and changing the shapes. You'll see that no matter what they look like they're doing, they never actually move, not even once.
Pausing the video will show the Gabors stuck in the same spots no matter which shape they are arranged in. So basically, no matter what the video looks like it shows, it's actually only showing one of these static shapes.
In case you feel like melting your brain a little further, check out the second-place and third-place illusions below.
If you brain still isn't fully melted, check out the rest of the top 10 illusions here at the Neural Correlate Society website.