It has been argued that if an animal is psychologically like us, there may be more scientific reason to experiment upon it, but less moral justification to do so. Some scientists deny the existence of this dilemma, claiming that although there are scientifically valuable similarities between humans and animals that make experimentation worthwhile, humans are at the same time unique and fundamentally different. This latter response is, ironically, typical of pre-Darwinian beliefs in the relationship between human and non-human animals. Another (...) irony is that debate about such issues has facilitated the participation once more of philosophers in questions concerning experimental psychology: ironic because laboratory-oriented psychologists, especially since the turn of the last century, had been eager to establish the independence of their subject from any influence of philosophy and its investigative methods, as well as from any kind of anthropomorphism.In Britain, certainly more so than in the United States, ethical constraints have prevented the development of psychological research with animals along certain routes. By the 1980s British professional and academic societies had published codes of conduct and guidelines for their members, in part responding to public concern about the welfare of animals in the psychological laboratory. What led to the establishment of these codes and guidelines? This paper analyses the historical background against which professional concern for ethical cost in experimental animal psychology began to take shape, leading to the societies’ open pronouncements of the 1980s. (shrink)