From replica to instruments: Animal models in biomedical research

The ways in which other animal species can be informative about human biology are not exhausted by the traditional picture of the animal model. In this paper, I propose to distinguish two roles which laboratory organisms can have in biomedical research. In the more traditional case, organisms act as surrogates for human beings, and as such are expected to be more manageable replicas of humans. However, animal models can inform us about human biology in a much less straightforward way, by being used as measuring devices - what I call their instrumental role. I first characterize this role and provide criteria for it, before illustrating it with some examples from biomedical research, especially cancer research. In such an instrumental role, phenotypes are not expected to phenocopy human phenomena, but instead have the purely instrumental value of detecting or measuring differences. I argue that the instrumental role is more prevalent than might first be suspected, and that some characteristics of contemporary biomedical research are increasingly shifting the use of laboratory organisms to the instrumental role. Finally, in light of the distinction proposed, I discuss the meaning of the expression "animal model".