[T]o the extent that we view morality as not simply a human creation, a device whose sole purpose is to ensure cooperation among humans, and thereby promote human flourishing, we have powerful reasons to reject the view that the interests of animals are less significant than the like interests of humans. Such a rejection will render much animal experimentation morally unacceptable. This is not a conclusion that will be eagerly embraced by the scientific community. It is, however, the conclusion best supported by a careful examination of the relevant moral reasons.
Alastair Norcross, ‘Animal Experimentation’, in Bonnie Steinbock (ed.), The Oxford Handbook of Bioethics, Oxford, 2007, p. 666
[T]he major source of useless experimentation, animal or otherwise, namely the dearth of clear original hypotheses, is still strong. This offers philosophers of science an opportunity of being kind to animals by way of being ruthless to mindless empiricists.
Mario Bunge, Ethics: the Good and the Right, Dordrecht, 1984
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