Meet Bob. He’s in his late fifties, a quiet guy, wears rimless spectacles, and likes to read poetry. Do you think Bob is a classics professor or a truck driver?
If you answered classics professor, you’re with the vast majority of people asked this question. Quiet, spectacles, poetry reader, all of it pretty well fits the common image of a classics professor and not so much our image of a truck driver. But while there are approximately 7500, maybe at a stretch 10000 classics professors in the US, that number is blown out of the water by a couple orders of magnitude when compared with how many truck drivers there are. The American Trucking Association’s website says there are 3,500,000 truck drivers in the country, making it much, much more likely that Bob is a quiet, poetry-reading truck driver. He may not fit the NASCAR-loving truck driver stereotype, but it’s still more likely.
It’s much more likely, but that’s not the way we think. Humans look for patterns, make categories, and form stereotypes in order to make sense of the world. If our early ancestors heard a scream, they did not sit down to calculate the probability that their friend Og had trod on a surprise thorn bush versus the probability that Og had just been snack for a saber-toothed tiger. No, they used their learned pattern of scream = bad and got the hell out of there.