translation.en: Something that Robert Provine has pointed out, as you can see here, and the reason why we were laughing when we heard those funny laughs at the start, and why I was laughing when I found my parents laughing, is that it's an enormously behaviorally contagious effect.
translation.zh: Robert Provine 指出的一些事情， 就像你在这儿看到的， 就是我们发笑的原因。 我们刚才听到的那些搞笑的笑声， 以及我在看到父母狂笑的时候，为什么会想笑， 是因为，它其实是一个巨大的 行为上的传染效应。