心力内投是一种防御机制，指把我们所欣赏的外部的或是他人的特质，品格等，结合到自身的行为，观念上来。

例子：有些神经症患者会通过模仿他人来减轻自身的焦虑。生活中，这种机制在群体中体现得比较广泛，群体人员之间互相模仿以更好地融入群体；朋友、夫妻之间相处久了也会越来越像。

安娜·弗洛伊德的自我心理学理论中认为，人的自我能够控制本我的力量，儿时父母或教师的期望，要求，理想会在儿童的内心发生心力内投，这时形成超我。

Introjection (German:Introjektion) is a psychoanalytical term with a variety of meanings. Generally, it is regarded as the process where the subject replicates in itself behaviors, attributes or other fragments of the surrounding world, especially of other subjects. Cognate concepts are identification, incorporation, and internalization. To use a simple example, a person who picks up traits from their friends (e.g., a person who begins frequently exclaiming "Ridiculous!" as a result of hearing a friend of theirs repeatedly doing the same) is introjecting.