The laugh is a lot like the "wow." It's that sound you make just because you're experiencing something, just because you're having a response to what's in front of you, something someone says.

这笑声很像“哇“这个字，是一种,因为正在经历某些事而发出的一种声音，作为你对面前发生的事或是，一些人说的话的反应。

耶鲁公开课 - 1945年后的美国小说课程节选

To make this a first order condition, I'm going to say "at the best response," put a hat over the 1.

为了达到一阶条件,我说在最佳对策下,在S1上写个帽

耶鲁公开课 - 博弈论课程节选