PHILADELPHIA (CBS) – There are some things in life you just can’t fake, and apparently, laughter is one of them – at least most of the time.

According to new research from UCLA, spontaneous (or real) laughter may be produced by different vocal systems than volitional (or fake) laughs.

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Scientists say they recorded forced laughter between friends as well as spontaneous giggles, and “participants could distinguish between spontaneous and volitional laughter” about two-thirds of the time.

“Quite a few fake laughs sound pretty good, but listeners seem to pay attention to certain acoustic features that are really hard to fake,” study author Greg Bryant, an associate professor of communication studies at UCLA, said on the school’s website.

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Furthermore, when researchers sped up the recorded laughs, participants tended to think they were more “real” and were fooled by the volitional laughs about half the time.

When the laugh recordings were slowed down, however, study subjects were unable to detect whether spontaneous laughs were made by humans or animals, but they were able to tell the fake laughs were human.

“These findings and acoustic data suggest that spontaneous and volitional laughs are produced by different vocal systems,” the study’s authors write, “and that spontaneous laughter might share features with nonhuman animal vocalizations that volitional laughter does not.”

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The study’s conclusions are published in the current issue of the journal Evolution and Human Behavior.