When it comes to laughs, the bigger the better, at least if you want it to spread. In one of those science-confirms-the-obvious studies, researchers found that open-mouth laughs in which people use their vocal chords in "vowel-like bursts" are the most contagious, LiveScience reports. And the longer they last, the more listeners like it (the laughter got ranked by college students). Breathy "courtesy" laughs or quiet chuckles got lower grades.
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