ABSTRACT
This chapter provides a description of a regulatory puzzle in personality psychology, which quite unexpectedly led to different puzzles in neurobiology and genetics, and now has turned to issues in clinical psychology. It focuses on issues of impulsive reactivity versus constraint, or deliberative control of action. Impulsiveness can yield physical danger. Impulses can interfere with attainment of longer-term goals. A different view derives from the idea that people process information in two somewhat distinct ways simultaneously, one more primitive than the other. The literature of personality psychology contains several dual process models, including what may be the earliest one in contemporary psychology: Epstein's cognitive-experiential self theory. The dual process idea has also been widely used in social psychology. Serotonin has been studied for some time, in both humans and other animals. There is also a substantial literature on the serotonin polymorphism and personality as assessed by broad-ranging self-report inventories. Low serotonergic function also relates to vulnerability to depression.
