The weirdest thing happened to me today. I had just gone for a run and after I went back inside and sat down, I noticed that the woodgrain on the end board of my bed frame looked as if it were moving, kind of warping toward the center. I looked up at the ceiling, which is slightly textured, and the same thing happened. It was really trippy and quite cool actually. After a bit of research, I found out that what I was experiencing is a visual illusion called “motion aftereffect” caused when you look at something that’s moving with your eyes still, for a while, and then look at something that is stationary. Here is an example:

I wondered why I had never experienced before. Did it have to do with how long I ran? I had run longer before, so maybe not? And apparently it can happen within minutes, down to milliseconds. And what about driving? It seems like that would be an obvious situation for it to happen.

For the running bit, here is my guess. Part of the reason may be that, in the past, I usually ran at night, and you can’t see things going by as well in the dark. But I think the main reason has to do with the fact that your eyes need to be stationary when you’re looking at the moving stimulus, in order for motion aftereffect to occur. During this particular run, I was listening to a Radiolab episode (yay Radiolab!) and because I was so engaged in listening, I wasn’t really looking at anything, my eyes weren’t moving. (Have you ever done the thing where you don’t focus your eyes on anything? It’s a really strange experience when you’re doing it consciously.) If I weren’t listening to the story, I would constantly be focusing on different things, my eyes would be moving around.

For the driving bit, I found an explanation here (halfway down the page). They propose that “if the motion covers the entire field of view of the eye, little or no motion aftereffect of any kind occurs.” They explain that the brain doesn’t perceive it as motion if your whole field of view is moving, which is because we detect motion by comparing the moving object to a stationary object or a stationary object with other parts of your field of vision moving in a different direction (ex. in video games). It’s a system that’s easily tricked apparently. Like when you see a car backing out when you’re parked next to it, and it looks like you’re rolling forward.

So there’s a lot more behind how motion aftereffect actually occurs and why it occurs. Look it up if you’re interested! In the meantime, here are some more cool examples: