In addition to his comedy, actor Kevin Hart owns a plant-based restaurant chain, a tequila brand and an entertainment and production company called HartBeat. The single thread between them all, and the "secret weapon" to his success, the 44-year-old said in a recently published MasterClass course: the power of humor. "Humor has acted like the master key to every door that I've [gone] through," said Hart. In much tougher moments, humor is equally valuable, Hart noted. Making people genuinely laugh boosts their output by up to 12%, found a 2015 study that Sgroi co-authored.

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Persons: Kevin Hart, Hart, you've, Daniel Sgroi, Warren Buffett Organizations: University of Warwick, CNBC, The University of Pennsylvania, Hong Kong University of Science, Technology