Twins are nature's living laboratories. Through them we are able to uncover new information concerning the genetic and environmental factors affecting who we are. Studies using identical and fraternal twins hold the keys to understanding our intellectual abilities, personality traits, social attitudes, and behavior. In Entwined Lives, Dr. Nancy Segal brings together cutting-edge information with illustrative case histories of twins and their families. In addition to the fascinating stories of identical twins reared apart and reunited as adults, Dr. Segal provides insights into the unusual language patterns of twins, how twin studies affect legal decisions, the role of fertility treatments in twin and "twinlike" conceptions, and more. This groundbreaking book explores the ways in which twins enhance our knowledge of human behavioral and physical development, while shedding new light on the nature/nurture debate and on the burgeoning field of evolutionary psychology.