A seemingly simple line and dot optical illusion by Akiyoshi Kitaoka, a professor of Psychology at the College of Letters, Ritsumeikan University, Kyoto, Japan, went viral online. Why? This black dot illusion can trip anyone up, as it shows a network of gray lines on a white background. Within this matrix, there are 12 black dots, each at the intersection of some gray lines. The maddening part about this is that you can't see all the black dots at once.
One reason we can't see all the dots at once is due to our not-perfect peripheral vision. The density of photoreceptors in our eyes plummets in our peripheral vision, meaning if you're not staring straight at something, it becomes a lot harder to make out. But you can also blame lateral inhibition. Because the black dots sitting at gray line intersections do not contrast as much, our brain washes over the dots with gray, rendering them invisible. To see it in action, check out the video below.