Now if you smiled to-- or make three people smile, and these three people-- each one makes three other people smile.

如果你的笑-,感染了三个人，这三个人-,每个人又引起另外三人发笑。

哈佛公开课 - 幸福课课程节选

Children are particularly influenced by the contagiousness of laughter, but just in general, if you hear somebody laughing, like the kids you saw before, it's the sort of thing that could easily make you laugh.

孩子特别容易,受笑声的感染，但普遍来说，如果你听到有人笑，像你们刚才看到的小孩子，这样的事物很容易引你大笑。

耶鲁公开课 - 心理学导论课程节选