abstract The sociophysiological perspective recognizes an intimate relationship and mutual regulation between human social and physiological systems that is especially clear in small groups. A fundamental argument made in this paper is that locations of actors in the social system, as defined by their relationships and by interactive processes found in small groups, are critical determinants of the brain's regulation of physiology and behavior. Relationships not only link the individual into the social system, but they provide information that is critical to the brain's regulation of the individual's physiology, psychology, and behavior. This review considers aspects of evolution and natural selection; presents examples of substantive bodies of literature; and focuses on brain mechanisms, including attention and hemispheric lateralization, that may be related to social processes. Sociophysiology represents an emerging subdiscipline within the field of sociology which has particular relevance to the study of small groups.