To test whether fake laughs are distinguishable from the real thing, UCLA researchers recorded spontaneous laughs between friends, as well as fake laughs. It turns out that you’re probably only convincing people with a fake laugh one-third of the time. When people let out a disingenuous chuckle, differences in speed and breathing make it more obvious that they’re faking it. MORE: The Depressing Thing That Makes Divorce More Likely “Quite a few fake laughs sound pretty good, but listeners seem to pay attention to certain acoustic features that are really hard to fake,” said study author Greg Bryant, an associate professor of communication studies at UCLA in a statement. When Bryant and his team sped up the fake laughs, they found that the faster they were, the more likely people were to think that they were real. Participants distinguishing between the laughter guessed wrong only half the time. MORE: The Real Reason Asian American Kids Outperform Whites Interestingly, in another experiment, the researchers slowed down the laughter and asked participants to say whether the laugh was from a human or an animal. Participants could not tell if real laughs were from a human or not. But they could definitely tell the fake laughs were human. “Across the animal kingdom, laughter signals ‘We’re in a play mode,’ " Bryant said. “In fact, laughter is thought to have evolved from labored breathing during physical play. In this way, genuine laughter reveals our animal nature.” If you want to hear what fake and real laughs sound like, listen here. The study is published in the journal Evolution and Human Behavior. This article was written by Alexandra Sifferlin and originally appeared on Time.com.