Lower mammalian species such as mice and rats, which most likely lack the lofty principles and motivations of humans, may care for their pups for the simple reason that it feels good to do so.

• 像大鼠及小鼠这种较低等的哺乳动物，并不像人类拥有崇高的原则与动机，牠们可能只是因为感觉良好而照顾幼儿。