What are the processes and mechanisms involved in interpersonal behaviour, and how are these constrained by human biology, social structure, and culture? Drawing on and updating classic sociological theory, and with special reference to the most recent research in evolutionary and neurophysiological theory, this work presents a unified, general theory of what happens when people interact. Despite modern technologies that mediate communication among individuals, face-to-face interaction is still primary. This book argues against recent social theory that postulates a dramatic change in the nature of human relationships under postmodernity and asserts that, despite undeniable and accelerating change in people's environments, certain basic human tendencies toward emotionally inflected, physically present social interaction remain strong. Turner builds on first principles he locates in the work of Mead, Freud, Schutz, Durkheim, and Goffman. After brief overviews of previous work on the embeddedness of social interaction in sociocultural systems and in human biology, each chapter presents elements of the microdynamics involved in encounters: emotions, motivations (transactional needs), culture (normative conventions), role processes, status, demographics, and ecology. each chapter ends with a series of testable propositions, which are streamlined into a series of summary priciples intended to motivate future research. The book concludes with some cautious hypotheses on the potential influence of micro-processes on broader social dynamics.