Book excerpt: The Psychobiology of Attachment and Separation provides an understanding of certain theoretical issues involved in social attachment and separation. The book brings together a number of investigators studying animal and human models of the psychobiology of attachment and separation. The contributors are actively conducting studies that incorporate physiological measures in attachment-separation paradigms. Thus, the book's unique features include reviews and interpretations of recent data on the physiological correlates of attachment and separation behavior in both animals and humans. The book is divided into two parts, one on animal models and one on human models. The first part reviews research from several animal species, including studies on the biology of maternal behavior and physiological, neurochemical, and neuroanatomical correlates of both attachment and separation. The chapters on animal models provide an overview of the state of knowledge on both the biology of social attachment and the biological correlates of separation. The second part presents reviews and new data on attachment and separation in human infants. A summary chapter examines both animal and human data and offers a synthesis of the results, including clinical implications and ideas for future research.