Genetic psychology, also known as behavioral genetics, is a category of psychology that investigates the genetic influence on human behavior. This field of study involves psychology, biology, genetics and statistics. Psychologists in this field analyze how much of an effect genetic inheritance has on a person's personality.
A relatively new interdiscipline, genetic psychology is in its initial stages of research. Theories surrounding behavioral genetics often address the issue of nature versus nurture. Following in the footsteps of Darwin, Francis Galton published Hereditary Genius: An Inquiry into its Laws and Consequences in 1869. Galton studied the intellectual and artistic genius of various English scholars, scientists, statesmen and artists. His goal was to demonstrate how the cognitive and behavioral talents are genetically inherited just as physical and biological traits are inherited: "I propose to show in this book that a man's natural abilities are derived by inheritance, under exactly the same limitations as are the form and physical features of the whole organic world."
Psychologists in this field favor analyzing twins separated at birth, noting what genetic traits dominate despite their disparate environments. Studies of twins have sparked the interest of geneticists and psychologists since the early 20th century. Identical twins share the most similar genetic makeup while fraternal twins share a lesser amount. On average, siblings share about 50 percent of their genetic makeup. Researchers examine three factors: additive genetics (inherited genes), common environment (similar experiences and backgrounds) and unique environment (the differences in their backgrounds). They can then determine what personality variances are inherited and what are based on environment.
Robert Plomin, author of Development, Genetics and Psychology, analyzes contemporary work of genetic psychologists. He notes the advances and setbacks of this field due to established assumptions. He says: "The mistaken notion that genetic influences begin prior to birth and remain immutable ever after pervades the field of developmental psychology... Once developmentalists realize that genes contribute to the instability that is predominant in most realms of child development, interest in behavioral genetics will grow."
Plomin claims that developmental psychology and genetic psychology must work hand in hand. There is still much to learn regarding genetic change during the span of human development. Developmental behavioral genetics has made significant advancements in the study of environmental influences. Plomin emphasizes a new concept that is bound to have a large impact on genetic psychology: "Environmental variance relevant to psychological development is not shared by members of a family... At the same time, this research consistently makes the point that the relevant environmental factors are not shared by children growing up in the same family. That is, children in the same family share no more similar relevant environmental experiences than do children taken at random from the population." Such an idea negates the foundations of nature versus nurture.
Many researchers attempt to apply the findings of behavior genetics to demographic studies. By applying the principles of genetic psychology to large populations, researchers are investigating what societal behaviors are hereditary. These behavioral traits include: fertility, longevity, divorce, alcoholism, smoking, homosexuality, femininity, aggression and obesity. Some researchers claim that genetic psychology is inconclusive and based on false assumptions. Daniel Courgeau and Atam Vetta, authors of Demographic Behaviour and Behaviour Genetics claim that "behaviour genetics confuses statistical concepts with genetic concepts. It is better to study the inheritance of a trait using the concept of the intensity of inheritance." They insist that molecular science contributes more to the study of demographic behavior than genetic psychology: "Molecular research suggests that human traits could be regulated by genes."
Some contest the study of genetic psychology on ethical grounds. Calum MacKellar, in his article "Ethics and Genetics of Human Behaviour," claims that "research in the genetics of human behavior can become a very sensitive and complex political issue. It has even been discouraged, in the past, as being potentially dangerous and disruptive to society." Communist and fascist regimes have taken undue advantage of behavioral psychology. The scientific pursuit of knowledge in these areas must remain objective, the application of this knowledge draws a fine line with unethical stances. There are pros and cons to the "medicalization" or classification of certain traits. MacKellar writes: "For some traits in which a certain amount of stigma is attached, the 'medicalization' of the traits could confirm the personal 'innocence' of those in the past considered responsible for the existence of these traits." On the other hand, some may equate genetic inheritance with inevitability, causing hopelessness and insecurity. Individuals may be discriminated against for inherited genetic traits while others may be praised.