Within the field of relationship science, there are numerous theories about personality at the intersection of social behaviors, with attachment theory occupying a large share of the attention in the literature. Though there are some theories that encompass interpersonal aspects of personality, none of these capture the full spectrum of this specific focus, leaving relationship scientists and social psychologists limited in their ability to delve into their research on these interdependent processes. This book explores the rich conceptual and empirical possibilities within current frameworks of interpersonal domains of personality and extends them beyond the current theories, using the interpersonal traits of dominance and nurturance as conceptual starting points. After introducing and evaluating these theories and the concept of agency (the intrapersonal) and communion (the interpersonal), the book applies geometric and psychometric analyses of these theories to examine interpersonal traits using the Interpersonal Adjective Scales-Revised Version (IAS-R) and the International Personality Item Pool-Interpersonal Circle (IPIP-IPC), ultimately examining the utility of interpersonal traits and interpersonal motives as predictors of accommodation in close relationships. The book concludes by comparing the expected and the observed results of these analyses concerning interdependence processes, guiding the reader through implementation and interpretation of sophisticated analyses in a thoughtful, forward-thinking way. The Self in Relationships is a comprehensive resource for relationship and social scientists interested in the interpersonal aspects of relationships and the interlocking processes involving personality characteristics (including previously under-explored ways of thinking about attachment orientations) and social behaviors.