They're trying to achieve satisfaction through their mouth of a sort they didn't get in this very early stage of development.

他们想通过这种口腔运动,来获得本该在口腔期获得的满足感。

耶鲁公开课 - 心理学导论课程节选

Freud uses it as an explanation for why somebody might eat too much or chew gum or smoke.

弗洛伊德用口腔期人格,来解释为什么会有人暴饮暴食,嚼口香糖或是抽烟。

耶鲁公开课 - 心理学导论课程节选