Experimental psychology raises, in an especially acute form, a central contradiction of much animal experimentation. For if the monkeys Harlow used do not crave affection like human infants, and if they do not experience loneliness, terror and despair like human infants, what is the point of the experiments? But if the monkeys do crave affection, and do feel loneliness, terror and despair in the way that humans do, how can the experiments possibly justified?

Lori Gruen and Peter Singer, Animal Liberation: A Graphic Guide, London, 1987, p. 81