I discovered this cool optical illusion through one of the Technology Review newsletters. Stare at the green dot in the image below — that part is meant to blink in and out of sight — and you'll notice that the 3 yellow dots will randomly seem to disappear themselves in various combinations.
The website where I found this, WhyEvolutionIsTrue.com, explains the phenomenon with help from a Nature News article titled, "A brain in doubt leaves it out." "The brain seems to have internal theories about what the world is like. It then uses sensory input – which tends to be patchy and disorganized – to choose between these. In some sensory situations, different theories come into conflict, sending our perceptions awry," the authors write. Essentially, this illusion captures one of those moments of motion-induced blindness when your brain accidentally discards the information it can't reconcile. There's a more detailed explanation at the link.