Professor Paul Bloom: I don't know if that's--The question is, "Is there a difference between smiling with your teeth versus just your lips closed?"

我不知道是否，问题是，微笑露齿与不露齿有不同吗“

耶鲁公开课 - 心理学导论课程节选

This characteristic thing we do with our lips exposing our teeth and so forth.

这种特有的,咧嘴露齿的动作

耶鲁公开课 - 死亡课程节选