Abstract: Research in comparative social cognition addresses how challenges of social living have formed the cognitive structures that control behaviours involved in communication, social learning and social understanding. In contrast to the traditional psychological approach, recent investigations take both evolutionary and functional questions into account, but the main emphasis is still on the mechanisms of behaviour. Although in traditional research `comparative' meant mainly comparisons between humans and other primates, ethological influences have led to a broadening of the spectrum of species under study. In this review, we evaluated how the study of dogs broadens our understanding of comparative social cognition. In the early days of ethology, dogs enjoyed considerable interest from ethologists, but during the last 20 years, dogs have rarely been studied by ethological methods. Through a complex evolutionary process, dogs became adapted for living in human society; therefore, the human environment and social setting now represents a natural ecological niche for this species. We have evidence that dogs have been selected for adaptations to human social life, and that these adaptations have led to marked changes in their communicative, social, cooperative and attachment behaviours towards humans. Until now, the study of dogs was hindered by the view that they represent an `artificial' species, but by accepting that dogs are adapted to their niche, as are other `natural' species, comparative investigations can be put into new light.