Abstract: The dangers of hypothesizing about unobservable cognitive mechanisms are well known to behavior analysts. I propose, however, that carefully fashioned cognitive theories that make predictions that are inconsistent with current behavioral theories can provide useful research tools for the understanding of behavior. Furthermore, even if the results of such research may be accommodated by modifying existing behavioral theories, our understanding of behavior is often advanced by the empirical findings because it is unlikely that the research would have been conducted in the absence of such cognitive hypothesizing. Two examples of the development of emergent relations are described: The first deals with the nature of a pigeon's 'representation' of two stimuli both of which are associated with correct responding to a third in a many-to-one matching task (stimulus equivalence or common representations). The second has to do with transitive inference, the emergent relation between two stimuli mediated by their relation to a common stimulus in a simultaneous discrimination.