Attachment has long been a key area of social development. Work on attachment processes has involved a variety of species as well as humans in diverse cultures and at various points in the life cycle. This volume presents research devoted to the meaning and implications of the attachment concept, including possible indices of attachment, the role of learning, whether or not attachment is best treated as continuous or discontinuous, and considerations for viewing attachment as a trait across environmental settings or as a process with functions that operate differently in disparate settings. Other psychological-process concepts, such as imprinting, relationships, and identification are also discussed. Because the contributors are active researchers and theorists, this volume may help establish trends and determine directions to shape literature on attachment for years to come.