The flashed face distortion effect is a wild ride that your very own brain will take you on when viewing flashing images of faces side by side. If you focus your eyes on either set of photos on one side of the screen, they will appear to be perfectly normal faces. But if you stare at that plus sign in the middle of the screen, it's like your peripheral vision decided to host a monster convention. Your brain exaggerates every little difference between the faces — normal foreheads look massive, eyes become weirdly symmetrical, and skin tones look like zombie flesh.
Why does my brain want to scare me like this? Turns out it's because our peripheral vision is bad at details, so our brain tries to fill in the gaps and ends up creating these grotesque caricatures. Our visual system is going completely haywire with all the rapid changes and crowded features.
Watching this alone at night was a bit creepier than I thought it would be. Seeing familiar faces morph into demons is preferable as a morning activity, with lots of sunlight and people around. Now I need to watch some silly cartoons to cleanse my mind's palette.
See also: Harpist with a distortion pedal
