Darwin and Tinbergen represent two enduring contrasts in comparative cognitive psychology: in the types of behaviors studied and the kinds of explanations sought. Darwin encouraged the search for human-like behaviors in animals as evidence for evolutionary continuity of mental processes. Tinbergen encouraged the careful causal analysis of animal behaviors as such and eschewed interpretations in terms of anthropomorphic processes. The Darwinian program has reemerged in contemporary research on comparative cognition. Its development and relationship to other areas of behavioral biology are traced. In using behavior as a window onto the animal mind, it is important to remember the lessons of Tinbergen and like-minded behaviorists in psychology. Several of the challenges that arise in attempting to show that other species share complex cognitive processes with humans are discussed in the light of the contrast represented by Darwin and Tinbergen, as are examples of how these approaches are being productively integrated.