Arguments for multiple realization depend on the idea that the same kind of function is realized by different kinds of structures. It is important to such arguments that we know the kinds used in the arguments have been individuated properly. In the philosophical literature, though, claims about how to individuate kinds are frequently decided on intuitive grounds. This paper criticizes this way of approaching kinds by considering how practicing researchers think about the matter. I will consider several examples in which (...) the practice of researchers on comparative vision conflicts with the standard account of these issues. (shrink)