Discussions of animal intelligence often assume, inappropriately, that intelligence is inherently good. In this case, it has turned out to be generally true. This chapter reviews absolute versus relational learning by suggesting that animals are capable of using either the absolute or relative properties of a stimulus in making discriminations. The ability of animals to develop emergent stimulus classes involving arbitrary stimuli has important implications for human language learning. The task most often used to study memory in animals is delayed matching-to-sample, in which following acquisition of matching-to-sample, a delay is inserted between the offset of the sample and the onset of the comparison stimuli. The accurate assessment of animal intelligence will require vigilance, on the one hand, to evaluate cognitive functioning against simpler accounts and, on the other hand, to determine the conditions that maximally elicit the animal's cognitive capacity.