“Most studies of nonmonogamous relationships focus on their composition and consequences. But how do people decide to abandon monogamy in the first place? What difficulties do people face in doing so? How might they make better choices? In this rich book, James K. Beggan answers these questions by blending his grasp of the empirical literature on triadic relationships with a helpful decision-theoretic framework. The reader leaves with a nuanced sense of the different motivations, reasoning, and moral concerns surrounding these potentially transformative decisions. If you study human intimacy, read this book.”

Luke Brunning, University of Leeds

Throughout The Decisions to Open A Relationship: To Three or Not to Three, Beggan delves, in meticulous detail, into the many (often obscure) theories, models and processes involved in human decision making. Beggan draws from psychology, economics, philosophy and game theory to weave together a far-reaching collection of ideas and frameworks while managing to tie each of them back to the matter at hand: whether to initiate the discussion of opening a formerly closed relationship….To the doctoral student writing their thesis: this book is a brilliant example of research writing and you should read it[.]

Journal of Sex & Marital Therapy