Scientists have uncovered more than 50 biases that, like this one, can mess with our thinking. For instance, there’s the “availability heuristic,” which makes us think something that’s easy to recall (because it’s emotional or because we’ve experienced it many times) is more common or probable than it really is. (Despite what you might think from watching CSI: Crime Scene Investigation, the world isn’t full of serial killers.) There’s also the “distinction bias,” which makes two options seem more different when considered simultaneously; the “denomination effect,” which makes us more likely to spend money when it’s in small bills or coins; and the “Dunning-Kruger effect,” which makes experts underestimate their abilities and laypeople overestimate theirs.

Source: Why You’re Biased About Being Biased