It’s not easy to get away with fake laughter. Science has shown our brains respond differently to genuine outbursts and forced chuckles, no matter how badly we want to believe our Oprah impressions are hilarious—or how badly we want to flatter someone.
What science hasn’t understood, though, is why our brains are so good at weeding out fakers. What about the way we laugh gives us away?
According to a new study in Evolution and Human Behavior, it’s all about timing. University California-Los Angeles’ Gregory Bryant and University of California-San Francisco’s Athena Aktipis recently came up with three experiments to test college students’ ability to differentiate between recordings of real and fake laughter played at different speeds. Here’s what they found:
- At normal speeds, people can tell whether laughter is authentic or forced about two-thirds of the time.
- When laughter is digitally sped up, it’s much more likely to be judged as genuine. In this case, fake laughter fooled listeners half the time.
- When laughter is slowed down, real laughter becomes indistinguishable from animal sounds, yet fake laughter remains recognizably human.
According to the researchers, these findings suggest our bodies actually create real and fake laughter through separate processes. “Genuine laughs are produced by an emotional vocal system that humans share with all primates," Bryant says in a press release. This system seems to have really strong control over our windpipes, so it allows us to shoot out quicker breaths of air when we laugh for real than when we fake it. We laugh faster as a result.
This speed difference between real and fake laughter is subtle, but not small enough to escape the perceptive powers we've honed over millennia of human evolution. Our senses are fine-tuned to pick up the most minute acoustic variations—and for good reason, Bryant and Aktipis write. Detecting feigned laughter is an important survival tool. “You have to be vigilant," Bryant says, "because you want to discern whether people are trying to manipulate you against your best interests or whether they have authentic cooperative intentions."
He and Aktipis actually go as far as declaring an unending "arms race" between humans' abilities to fake laughter and to detect it when it's bogus, which makes the dramatic but true point that we certainly continue to use laughter to gain people's favor. Of course, our intentions need not be devious. We may just not want to look like jerks.
More work remains to refine our understanding of the neurological underpinnings of different laughs, the researchers note. But if you can't find a way to convince yourself your boss' next bad joke is funny, at least you now know to laugh really fast.