Why 'Poop' and 'Wiggle' Are Funny Words, According to Science

To do it, Westbury analyzed words in two different ways: by their meaning and by their form. For the first analysis, the researchers looked at "semantic predictors" that group words with similar meanings. Using a free tool developed by Google that identifies words that are commonly used for one another (co-occurrence), Westbury mapped out the semantic relationships between 234 of the funniest human-picked words. From this "correlation plot," the researchers identified six different clusters or categories of funny words: insult, sex, party, animal, bodily function and expletive.

Now this is where things get dangerously mathematical. Since many of the words on the human-rated funny list fell into more than one category, the researchers needed a more precise measurement of how a word's meaning translated into comedy. Using the Google tool, they came up with lists of words most closely related to each of the six categories. Then they came up with average values for each of those word categories using something called linear regression analysis. Those average values for each category — insult, sex, expletive, etc. — became known as "category-defining vectors."

When looking specifically at meaning, it turns out that the funniest words don't necessarily fall cleanly into the most categories, but are the words whose mathematical values are the closest, on average, to those six category-defining vectors. Confused? Here's how Westbury summed it up in a press brief: "The average similarity of a word's meaning to these six categories is itself the best measure we found of a word's funniness, especially if the word also has strongly positive emotional connotations."

But meaning is only one type of measurement. Westbury and his team looked at the form of funny words, things like word length or the individual sounds (phonemes) that make up each word. In this second analysis, the data fit nicely with the incongruity theory of humor. It turns out that the fewer times a word or its phonemes appear, the funnier we think they are. That helps explain why there are so many "k" and "oo," sounds in the funny word lists. They're statistically improbable. Words ending in "le" (like waddle" and "wriggle") were another source of fun, suggesting as the study puts it, "repetition, usually with a diminutive aspect."

Now this is where things get really interesting. The human brain, it seems, is running all of these complex mathematical models all the time without any of us knowing it. As we watch TV and read and talk to people, our brains are constantly parsing language for subtle semantic cross-connections and statistical probabilities. And the result — at least on this basic, one-word level — is what we call humor.

"If I asked, 'Which letter is more common, 'p' or 'b'?' I think the average person would have no clue consciously. But unconsciously, they are sensitive to that," says Westbury. "And we know that, because their funniness judgments are reflecting exactly that kind of fine-tuned calculation."

In other words, says Westbury, "People are using emotions to do math."

Westbury argues that all of this makes perfect sense evolutionarily. Our brains have been hard-wired over millions of years to identify anything that's out of the ordinary as a potential threat. And human emotions, including humor, likely developed as ways of responding to improbable events and environments.

"People laugh based on how improbable the world is," says Westbury.

Of course, it's a long conceptual leap from predicting the funniness level of individual words to modeling the comedic mechanics of a knock-knock joke or a salty limerick. But Westbury's work points the way. Maybe someday we'll finally understand why that chicken crossed the road. One thing's clear, though. A frog wouldn't have been half as funny.