Real or Fake? Humans Can Tell if Laughter is Genuine

Can you tell if someone is only faking their laughter? It turns out that you just might be able to. Scientists have found that a genuine laugh actually employs a different vocal set than a fake laugh.

"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 Greg Bryant, one of the researchers, in a news release.

In this case, the scientists recorded the spontaneous conversations of college roommates. From these recordings, the researchers collected 18 spontaneous laughs; they then collected 18 forced laughs that were the same length as the genuine ones.

The researchers then set up the recordings and played them to participants. In the first round, they were asked to determine whether the laughs were real or fake; then, the scientists sped up and slowed down the recordings in order to see if they could tell the difference. It turned out that the volunteers were only fooled 37 percent of the time by the fake laughs.

"Genuine laughs are produced by an emotional vocal system that humans share with all primates, whereas fake laughs are produced by a speech system that is unique to humans," said Bryant in a news release. "Altering the speeds of the two types of laughs helps highlight the distinct properties of both vocal systems."

The findings reveal that fake laughs and real laughs are not only different, but can also be identified by others. The fact that they're created through different vocal systems also reveals how great the difference is biologically. The speech system, which is responsible for fake laughs, controls the dynamics of the vocal tract differently and can't open and close the windpipe as quickly.

The findings are published in the journal Evolution and Human Behavior.