Behavior genetics ? The branch of genetics that examines the genetic and environmental contributions to personality characteristics and behavior Behaviorism ? A theoretical perspective that focuses on observable, quantifiable behavior and the relationships between behavior and environmental variables Cognitive perspective ? the branch of psychology that deals with thought processes such as memory and language Evolutionary perspective ? the study of the evolution of behavior using the principles of natural selection Functionalism ? a movement in psychology led by William James in which consciousness was study according to the functions it serves, rather than its structure