Behavioral genetics and evolutionary psychology: Unified perspective on personality research

Human Biology, Apr 1998 by Segal, Nancy L, MacDonald, Kevin B

Besides system x situation interaction, there can also be system X system interaction, that is, interactions between systems at the physiological level. For example, there is evidence of mutual inhibitory influences between the mechanisms underlying behavioral inhibition and behavioral approach. Mesulam (1986) described reciprocal inhibition between the frontal and parietal lobes; the parietal lobe was viewed as an approach system characterized by diffuse attention and impulsive responding. Gray (1987) also noted reciprocal inhibitory influences between the behavioral inhibition system (BIS) and the reward-based approach system, and in the rat at least, the inhibitory influences from the BIS are more powerful than in the rewardbased approach system. Both systems can be aroused in particular situations, as when a previously rewarded behavior is punished. Tucker and Derryberry (1992) also emphasized the inhibitory role of the frontal cortex. They noted that individuals with frontal lesions are prone to impulsive responding, to the "disinhibition syndrome" (Luria 1980), and to inadequate anticipation of aversive outcomes.

The model implied by the evolved systems perspective is therefore useful for conceptualizing conflicts between evolved systems and for situation specificity. For example, the behavioral approach associated with dominance and sensation seeking and the behavioral avoidance systems associated with conscientiousness/behavioral inhibition are psychometrically independent, implying that individuals can be more or less sensitive to rewards and more or less sensitive to punishments and deferring gratification. Nevertheless, each system has inhibitory effects on the other system, so that in a situation with both potential rewards and potential punishments both systems are activated. Individuals high on dominance and sensation seeking evaluate the risks involved and engage in behavioral approach. In contrast, introverts, being less attracted to the potential rewards, are more likely to have approach tendencies inhibited by mechanisms underlying conscientiousness, such as Gray's (1982) BIS. A situation characterized overwhelmingly by potential danger activates the BIS, even for individuals moderately high on dominance and sensation seeking, whereas a situation characterized overwhelmingly by potential reward with little risk activates the reward-approach systems, even for individuals with powerful inhibitory tendencies. The result is what one might term system X trait X situation variation, in which the system is understood as a universal mechanism responsive to particular perceived environmental contingencies, and the trait represents individual differences in proneness to activating particular systems.

Within the perspective developed here, personality is intimately bound up with affect and motivation. Among humans this conceptualization would be compatible with a hierarchical model in Emmons's (1989) sense. Specifically, behavior related to personality occurs at several levels, based ultimately on the motivating aspects of evolved personality systems. For example, the emotions of anxiety and/or relief consequent to achieving safety are central to mechanisms designed to avoid perceived danger. Within Emmons's (1989) scheme these emotions act as motive dispositions. People are able to engage in a wide range of lower-level behaviors directed at approaching or avoiding these affective motive dispositions. Humans are thus able to deduce imminent danger by using an elaborate array of open-ended general-purpose information processing mechanisms and learning (e.g., uncovering an elaborate plot as a result of sophisticated knowledge of computers). This appraisal of imminent danger would then trigger the BIS, checking behaviors, and feelings of anxiety. Humans are also able to devise a variety of flexible openended strategies that are not significantly constrained by evolutionary processes in an attempt to lower their anxiety (e.g., formulating an elaborate scheme to escape imminent danger).