In the video below, mathematician Tadashi Tokieda shows us an interesting effect that happens when you take random dot patterns, photocopy them on transparency, then overlay and rotate the images. The effect is startling, as your brain assigns meaning and creates patterns in the randomness. So where does this come from? Watch and learn, as Tokieda shows the effect across a variety of kinds of dots (by five minutes in, he's using a lattice of triangles, and it's utterly bizarre).