Some of the most intriguing issues in the study of cognitive, social, emotional, and physical development arise in the debate over nature versus nurture; a debate difficult to resolve because it is difficult to separate the respective contributions of genes and environment to development. The most powerful approach to this separation is through longitudinal adoption studies. The Colorado Adoption Project (CAP) is the only longitudinal adoption study in existence examining development continuously from birth to adolescence, which makes it a unique, powerful, and tremendously valuable resource. CAP is an ongoing assessment of 245 adopted children and 245 biological control children assessed from birth to early adolescence. This book is the fourth in a series describing CAP results. This latest volume, edited by four eminent researchers in developmental psychology, builds on the large body of research already generated by investigating the role of genes and environments on early adolescent development.