From a psychological point then, animals have evolved to be nice to their kin, particularly their children, and particularly in birds and mammals.

从心理学角度看，动物进化趋向于对自己的亲人有益，特别是自己的孩子，以鸟类和哺乳类为代表。

耶鲁公开课 - 心理学导论课程节选

For birds and mammals, we don't have many kids but so we devote a huge amount of psychological energy to protecting the ones that we have.

鸟类和哺乳类，没有很多孩子,所以我们用大量的心力,去保护我们有的孩子。

耶鲁公开课 - 心理学导论课程节选