A comparative method of studying the biological bases of personality compares human trait dimensions with likely animal models in terms of genetic determination and common biological correlates. The approach is applied to the trait of sensation seeking, which is defined on the human level by a questionnaire, reports of experience, and observations of behavior, and on the animal level by general activity, behavior in novel situations, and certain types of naturalistic behavior in animal colonies. Moderately high genetic determination has been (...) found for human sensation seeking, and marked strain differences in rodents have been found in open-field behavior that may be related to basic differences in brain neurochemistry. Agonistic and sociable behaviors in both animals and humans and the trait measure of sensation seeking in humans have been related to certain common biological correlates such as gonadal hormones, monoamine oxidase (MAO), and augmenting of the cortical evoked potential.The monoamine systems in the rodent brain are involved in general activity, exploratory behavior, emotionality, socialization, dominance, sexual and consummately behaviors, and intracranial self-stimulation. Preliminary studies have related norepinephrine and enzymes involved in its production and degradation to human sensation seeking. A model is suggested that relates mood, behavioral activity, sociability, and clinical states to activity of the central catecholamine neurotransmitters and to neuroregulators and other transmitters that act in opposite ways on behavior or stabilize activity in the arousal systems. Stimulation and behavioral activity act on the catecholamine systems in a brain–behavior feedback loop. At optimal levels of catecholamine systems activity (CSA) mood is positive and activity and sociability are adaptive. At very low or very high levels of CSA mood is dysphoric, activity is restricted or stereotyped, and the organism is unsocial or aggressively antisocial. Novelty, in the absence of threat, may be rewarding through activation of noradrenergic neurons. (shrink)

Depue & Morrone-Strupinsky (D&M-S) have elaborated a detailed description of the motivational system for affiliation and its neurological basis. This “bottom-up” approach, based almost entirely on studies of nonhuman species, fails to connect with personality differences at the human level. A “top-down” approach looks for common biological markers in human and nonhuman species and relates these to behavior in both.

Is a generalized positive incentive motivation a construct appropriate to the human level of behavior or would sensation or novelty seeking be a more appropriate one? Is positive incentive motivation, or susceptibility to signals of reward, a mechanism related only to extraversion traits including sociability, activation, social potency, and positive affect? Research shows that susceptibility to reward is related to impulsive sensation seeking and aggression as well as sociability and an aroused type of positive affect. Comparative and indirect human correlates (...) suggest an involvement of dopaminergic reactivity in sensation seeking and sociability. (shrink)

Psychopathy has as its central traits socialization, sensation seeking, and impulsivity. These are combined in a supertrait: Impulsive Unsocialized Sensation Seeking (ImpUSS). Secondary types are defined by combinations of ImpUSS and neuroticism or sociability. All broad personality traits have both genetic and environmental determination, and therefore different etiologies (primary as genetic, secondary as environmental) for primary and secondary sociopathy are unlikely.