The rim shot after a comic remark is an attempt to simulate--sort of a pre-technological attempt to simulate the sound of laughter.

讲完笑话，紧接着一阵鼓声,也是为了引起…,引起观众大笑的一种原始手段。

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