In November 2020, the usual dark wet of fall settled into Seattle—and with the pandemic raging and outdoor gatherings less appealing, my social life took a nosedive. To fill my evenings, I decided to take on those things I always said I’d do if only I had more time, like practicing my Chinese. While I grew up speaking Mandarin, I’d never mastered reading or writing characters, so I fired up my long-neglected Duolingo account and committed to doing at least a lesson a day.
Whether you’ve already got some language proficiency under your belt or are starting out as a complete beginner, Duolingo doesn’t teach languages the way you might have learned them in school, with lists of vocabulary and verb conjugations. Instead, it makes you jump right in and start matching words with their meanings or translating sentences. My lessons started out simply enough with new vocabulary and phrases to practice grammar—and occasionally, there was a sentence that made me chuckle, like, “He is handsome but not a good person,” or “There are too many people here.” Then there were some that made me unexpectedly emotional in the context of the pandemic. There was “This year I cannot celebrate Chinese New Year with my family,” and this simple but terrifying question: “Are you happy?” Soon enough, though, my lessons veered into the absurd. I could imagine very specific scenarios in which I’d need to know how to say “he drank three bottles of Baijiu and he is sleeping now” or “I have 1,500 cat photos on my phone,” but they hardly seemed like the kind of sentences I’d need to know how to write in the long term.
A quick Google showed I was not the only one curious about these weird sentences. No internet phenomenon is complete without a dedicated Tumblr and Twitter accounts to document it; users submitted their own nonsensical sentences, like “The bride is a woman and the groom is a hedgehog,” or “The man eats ice cream with mustard.” Others conveyed existential angst, like “I am eating bread and crying on the floor” and “Today I will gaze into the distance and cry as well,” both nominated by Duolingo users as the “most 2020 phrases.” Clearly, these goofy sentences were some kind of strategy—but what, exactly, is Duolingo trying to accomplish with them?
To find out, I went straight to the source. Cindy Blanco, a learning scientist at Duolingo, explained that the company’s content is generated by language-specific teams, each of which has their own quirks. Lessons in Norwegian and Swedish, for instance, often include references to ’90s grunge music. Some teams have always enjoyed sneaking in weird or funny sayings, but over time, course creators made an explicit decision to include them on the theory that weird sentences have the potential to boost learning. I asked how, exactly, that would work, and Blanco explained that people often learn best when there’s a mismatch between what they expect and what they actually encounter. “When there’s a conflict between your expectation and the reality, that triggers responses in the brain,” said Blanco. “It forces you to attend more carefully to what you’re seeing.” For example, when you see a sentence like, “The bride is a woman and the groom is a …,” your brain has likely filled in the word man, so the actual word Duolingo uses—hedgehog—is a surprise. Voila, you have been forced to pay extra attention.
Sam Dalsimer, Duolingo’s global head of communications, told me this approach is based in part on research conducted by a team of psychologists from Ghent University in Belgium, which was published in PLOS in 2018—so I got in touch with the paper’s authors. Tom Verguts, a Ghent psychology professor who heads up the lab where the research was conducted, told me he’d never heard of Duolingo, and wasn’t aware that researchers there were familiar with his work. He seemed pleased that his research had been of use, though, and he agreed that the “extrapolation” Blanco and her team were assuming could hold water.
Verguts’ paper studied what researchers in the field call “reward prediction errors”—the concept that learning happens when you encounter an unexpected outcome. (Again, think hedgehog instead of groom.) There’s plenty of evidence that surprise helps rats or primates passively learn things like how to get a treat, but Verguts and his colleagues wanted to see whether reward prediction errors could improve humans’ ability to learn something intentionally, like new vocabulary. To do so, the researchers taught Dutch speakers Swahili vocabulary in a method Duolingo users might recognize: A computer program would show a Dutch word and then provide either one, two, or four Swahili words for the user to select as the correct translation. Since these Dutch speakers didn’t know Swahili, each selection was essentially a guess, and after each guess, the participant got feedback on whether they guessed correctly. Once participants ran through the program, they were tested on their recall of the correct words.
It turned out that people who had been given four options actually performed better on the final test. Verguts concluded that this was because when those people guessed the correct answer out of four options, they were more surprised than those who chose from two options. (And participants who only had one option had zero surprise at all.) “You can only learn by making a prediction,” says Verguts, and when given four options, it’s more unexpected that you will have chosen the right match. That unexpected outcome—i.e., a reward prediction error—is more surprising, and might serve as a type of reward that drives stronger learning.
Silly or funny sentences are similarly unexpected, and could play a similar role in language learning. “My interpretation is that humor is a type of weak ‘prediction error,’ ” says Verguts. Predictable sentences—say, “The bride was a woman and the groom was a man”—are commonplace and unremarkable. Wildly erratic sentences (what linguists would call “semantically unpredictable sentences”) are usually just absurd, like “The table walked through the blue truth.” But something in the middle is where humor lies, Vergut speculates. “The bride is a woman and the groom is a hedgehog” is a perfect example of that sweet spot in between rote and nonsensical.
To Vergut’s knowledge, there aren’t any studies directly looking at whether playfulness or humor can boost learning. What literature I did find were reports—not studies—from language teachers working in a classroom, not an app. I asked Nicole Holliday, an associate professor of linguistics at the University of Pennsylvania and host of Slate’s linguistics podcast Spectacular Vernacular, why researchers haven’t delved into the link between learning and humor. One reason? “Things that are funny are not funny to everyone,” she says. While I find the absurdity of encountering “I sell refrigerators, do you understand?” in a lesson laugh-out-loud funny, others might disagree. It’s really hard to quantify humor—and it’d be even harder to tease apart what role our subjective appraisal of humor actually has in learning, in addition to the many other factors that go into language learning. “Adults are not blank slates,” Holliday says. “There’s a lot of variation in people’s natural language acquisition ability and motivation.”
Despite a lack of pointed studies about this, Holliday says humor might boost learning just through increasing people’s motivation to learn. It’s simple: If you see something amusing on Duolingo, you’re probably more likely to enjoy the experience, and then to come back and use the app more. You might also come back to a particularly interesting sentence later; for instance, Holliday says that she screenshots funny sentences, or recounts interesting stories about the app’s characters. That reinforces her learning—and makes her want to keep going in her lessons. That’s particularly important for an app like Duolingo, which competes with the myriad other shiny, addictive apps on your phone. “Our users can open up TikTok,” says Dalsimer. (By the way, if you haven’t already seen Duolingo’s borderline unhinged videos and comments on TikTok, they’re worth checking out.)
Holliday also points out that weird sentences are just part of learning language. The beauty of language is its infinite capacity to convey anything we might experience or imagine. People wind up using novel combinations of words all the time; I keep a list of delightful English phrases I come across that I suspect had never before been uttered in the history of the language. (My favorite two from the last year are “Hot Pockets heiress” and “regime-occupied Safeway.”) And let’s be real—given the state of the world, it might be worth knowing how to say “I am eating bread and crying on the floor” in multiple languages.