There's research, not on tea natures or even young adults, but in the work place, that emotion is contagious. And mimicry is actually this hard wired human response. So, you come on, you're in a really high energy, positive mood. Without even my conscious awareness, i start mimicking your tone of voice, your body land yor facial expressions. And then i actually start to feel the emotions that iam behaviorly mimicking.
Also: which professions have the happiest people?