This chapter examines the contribution of genes to the potentialities of the individual and reviews biological systems that support personality development and functioning. We quite intentionally cast the scientific problems to be solved in terms of contributions, potentialities, and support. We hope at the outset to bypass outmoded dichotomies and to avoid simple statements about how genes determine behavior. The field must move beyond formulations that pit nature against nurture or maturation against learning. Such formulas falsely dichotomize factors that actually work together. They deflect psychology's attention from scientific advances in understanding the processes through which biology and culture coact. Extraordinary progress in the fields of molecular genetics and neuroscience in the past 20 years has revealed a subtle interplay of genetic and experiential processes (Gottlieb, 1998). As we consider the role of genetic factors and biological systems in personality, we can do so from the basis of a firm consensus that the biological organism dynamically interacts with the environment throughout the life course.

An understanding of biological potentialities and constraints is important not just for its own sake but because it may enable one to exploit environmental opportunities for personal growth. The recognition that biology and experience influence one another raises new questions about how behavioral experiences can compensate for inherited liabilities (Brown, 1999; Nelson, 1999). It also bears on classic questions. To what extent are organisms born with behavioral capacities built in?