ABSTRACT
To some in the functional school of psychology of the early twentieth century, the theory of evolution gave reason to believe that behavior, as much as morphology and biochemistry, served as means of “fitness.” Thus, instinct became as valid a criterion for fitness as length of a limb, rate of a biochemical reaction, etc. This led to a circularity of reasoning that gave the ammunition to the behaviorist school of psychology to eschew all things innate as concerns behavior. Accordingly, the environment was the sole source of behaviors, including their differences in expression and development. For many years, the environmentalist view of acquisition
and development of behavior dominated the discipline of psychology in America. Even today, the mere mention of genes as influencing behavior elicits skepticism. In Europe, behavioral biologists took a more heredity-friendly view of behavior and its development, and a great deal of debate ensued between the groups. A modern synthesis of the best of the thinking on both sides has lent credence to the notions that (1) genes do in fact influence behavior, (2) genes interact with the environment and with each other, and (3) the actions of genes and their interactions are accessible for study.
