Is behavior learned? Is it innate? What about aggression, intelligence and madness? There is a crucial relationship between how humans behave toward others and how they view life. Interest in behavioral genetics depends on wanting to know why people differ. According to Jack R. Vale, in Genes, Environment, and Behavior, recognition of the importance of hereditary influence on behavior represents one of the most dramatic changes in the social and behavioral sciences over the past two decades. . A shift has begun toward a more balanced contemporary view that recognizes genetic and environmental influences on behavior. Behavioral genetics lies in its theory and methods, which take into account both genetic and environmental sources of behavioral differences between individuals. Behavioral genetics is simply the intersection between genetics and the behavioral sciences. Behavior is a phenotype, that is, an observable characteristic that we can measure. On the other hand, the behavior is not just another phenotype. According to Robert Plomin in Behavioral Genetics, "Because behavior involves the action of the entire organism rather than the action of a single molecule, a single cell, or a single organ, behavior is the phenomenon the most complex that can be studied genetically. Unlike some physical characteristics, behavior is dynamic, changing in response to the environment. Indeed, behavior is at the forefront of the evolutionary text because it emphasizes the complexity of behavioral phenotypes” (2). Obviously, there cannot be behavior without both an organism and an environment. For a particular behavior, what causes differences between individuals? For example, what causes individual differences in c...... middle of paper ......al; Human studies. Boston: Little, Brown, 1970. Print.Eaves, Lindon J., Judy L. Silberg, Joanne M. Meyer, Hermine H. Maes, Emily Simonoff, Andrew Pickles, Michael Rutter, Chandra A. Reynolds, Andrew C. Heath, Kimberly R. Truett, Michael C. Neale, Marilyn T. Erikson, Rolf Loeber and John K. Hewitt. “Genetics and Developmental Psychopathology: 2. The Main Effects of Genes and Environment on Behavior Problems in the Virginia Twin Study of Adolescent Behavioral Development.” Journal of Child Psychology and Psychiatry 38.8 (1997): 965-80. Print.Plomin, Robert, JC DeFries and GE McClearn. Behavioral genetics: an introduction. New York: WH Freeman, 1990. Print. Rothstein, Carson. Behavioral genetics. Baltimore: John Hopkins UP, 1999. Print.Vale, Jack R. Genes, environment and behavior: an interactionist approach. New York: Harper & Row, 1980. Print.