SOURCE: University of California, Los Angeles, news release, May 5, 2014
THURSDAY, May 8, 2014 (HealthDay News) -- Fake laughter fools other people only about a third of the time, a new study says.
What gives phony mirth away? It's probably tiny clues in your breathing, according to Greg Bryant, an associate professor of communication studies at the University of California, Los Angeles who conducted the study.
"Quite a few fake laughs sound pretty good, but listeners seem to pay attention to certain acoustic features that are really hard to fake," he said in a university news release.
Bryant recorded 18 genuine laughs and 18 fake laughs. He played the laughs to a group of college students, who were asked if the laughs were fake or real. The students were fooled by just 37 percent of the fake laughs.
Laughs consist of two parts: the vowel sounds in "Ha, ha, ha," and the breathy sounds of air between the vowel sounds, Bryant explained. He found that real laughs have a higher proportion of breathy parts than fake laughs do.
The researchers also played the laugh recordings for the students at faster and slower speeds. When they sped the laughter up, the students could only detect the fake laughs about half the time. When the recordings were slowed, the students had a hard time recognizing whether the real laughs were made by humans or animals. But, they were able to discern that the fake laughter was made by humans.
The findings suggest that real and fake laughs are made by two separate vocalization systems. And while some animals laugh, only people know how to fake a laugh.
"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," Bryant said.
The study was published in the journal Evolution and Human Behavior.
People have evolved an ability to detect fake laughter because it can be used by some to take advantage of others, Bryant explained.
"You have to be vigilant, because you want to discern whether people are trying to manipulate you against your best interests or whether they have authentic cooperative intentions," he said.
Helpguide.org explains the health benefits of laughter and humor.