More broadly, this theoretical work may have implications for efforts to develop more complete explanations for the emergence of individual differences in behavior. We believe that rapid advances in the fields of molecular genetics, brain neurochemistry, brain structure, and precise trait definition are making it far more possible to understand the facilitative conditions for the emergence of important psychological traits than ever before. That we were able to identify well-validated programs of research pointing to relevant brain systems, the neurotransmitter activity within those systems, and gene polymorphisms related to the neurotransmitter activity—and tie those to research distinguishing urgency from other traits--provides an example of what is becoming increasingly possible.
