He said later that he did so because he was finding it difficult to bring up the question of surrender.

VOA: special.2009.12.24

And his big finding is that you could separate people-- you could separate the question of laughter from the question of a joke or the question of humor.

他有一个重大的发现,你可以区分…,你可以区分什么是笑,什么是玩笑，什么是幽默。

耶鲁公开课 - 心理学导论课程节选