Is self-cognizance a uniquely human attribute, or do other animals also have a sense of self? Although there is considerable interest in this question, answers remain elusive. Progress has been stymied by misunderstandings in terminology, a focus on a narrow range of species, and controversies over key concepts, experimental paradigms and interpretations of data. Here, we propose a new conceptual and terminological framework, emphasizing that degrees of self-cognizance differ among animals because of the cognitive demands that their species-specific social structures and life-history characteristics have placed upon them over evolutionary time. We suggest that the self-cognizance of an organism falls at a point on a continuum of social complexity and conscious involvement.