It's mock aggression in the sense that when people laugh they're often teasing, kidding around.

我们知道打闹是装出来的，因为人一笑,我们就知道他们是闹着玩的。

耶鲁公开课 - 心理学导论课程节选

It's also-- a lot of laughter isn't caused by incongruity so a lot of times when we laugh there's nothing incongruous in any deep sense about it.

还有…,很多笑不是因为不一致引起的,很多时候我们笑,并不是因为其中有不一致的现象。

耶鲁公开课 - 心理学导论课程节选

Why do we know that? Because it's loud.

我们怎么知道的？因为笑很大声。

耶鲁公开课 - 心理学导论课程节选

This is what--this is where the humor for that baby comes in, which is you couldn't predict when the sound was coming and some aspect of that was what made it so funny then, what elicited the laughter.

这就是…,为什么那些婴儿那么好笑，因为你猜不到他们什么时候会笑,因此我们才觉得好笑，引起我们大笑。

耶鲁公开课 - 心理学导论课程节选