Behavioral genetics and evolutionary psychology: Unified perspective on personality research

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

NANCY L. SEGAL1 AND KEVIN B. MACDONALD2

Abstract Behavioral geneticists and evolutionary psychologists have generally pursued human behavioral analyses with little theoretical or methodological exchange. However, significant benefits might accrue from increased communication between these disciplines. The primary goals of this article are (1) to identify meaningful junctures between behavioral genetics and evolutionary psychology, (2) to describe behavioral genetic research designs and their applications to evolutionary analyses, and (3) to reassess current personality research in light of behavioral genetic and evolutionary concepts and techniques. The five-factor model of personality is conceptualized as subsuming variation in normative species-typical systems with adaptive functions in the human environment of evolutionary adaptation. Considered as universal evolved mechanisms, personality systems are often seen in dynamic conflict within individuals and as highly compartmentalized in their functioning between settings. However, genetically influenced individual differences in personality may also be understood within an evolutionary framework. Studies of the heritability of personality traits indicate broad-sense heritabilities in the 0.40-0.50 range with evidence of substantial nonadditive genetic variation and nonshared environmental influences. Evidence indicates that evolutionary theory (e.g., inclusive fitness theory) predicts patterns of social interaction (e.g., cooperation and bereavement) in relatives. Furthermore, variation in personality may constitute a range of viable strategies matching the opportunities available in the complex niche environment of human societies. Within this wide range of viable strategies, personality variation functions as a resource environment for individuals in the sense that personality variation is evaluated according to the interests of the evaluator (e.g., friendships, coalitions, or mate choice).

KEY WORDS: EVOLUTIONARY PSYCHOLOGY, PERSONALITY TRAITS, BEHAVIORAL GENETICS, FIVE-FACTOR MODEL OF PERSONALITY

Behavioral genetics and evolutionary psychology remind us of ships passing in the night. For the most part, issues and problems have been separately pursued with little reference to the rich set of concepts and methods that each might offer the other. Formal definition of both these disciplines has been recent, yet progress has been swift. Accumulation of new data and interpretations has been impressive and reappraisal of existing material has been exciting. These developments have not gone unnoticed: A modest cadre of researchers [e.g., Freedman (1968), Buss (1987, 1990), Crawford and Anderson (1989), Belsky et al. (1991), Mealey and Segal (1993), Segal (1993), Rowe (1993), and Scarr (1995)] have persuasively argued that there is territory for fruitful exchange between these natural allies. Unfortunately, attempts at reconciliation are long overdue because of theoretical and methodological differences, or what Scarr (1995) has termed differences in intellectual geography. The primary goals of this article are (1) to identify meaningful junctures between behavioral genetics and evolutionary psychology, (2) to describe behavioral genetic research designs and their applications in evolutionary analyses of behavior, and (3) to reassess current personality research in light of behavioral genetic and evolutionary concepts and techniques.

The five-factor model (FFM) has received a great deal of support within personality psychology [e.g., Digman (1990)], and our ideas will draw heavily on the FFM literature. The FFM emerged from factor-analytical studies of English-language trait descriptors. Across a wide variety of studies of trait descriptive terms five factors consistently emerge in self-ratings or ratings by observers (Goldberg 1981, 1992). The FFM derives from a large and representative set of trait descriptors, not only in English but also in other languages, suggesting that the FFM can be generalized cross-culturally. In addition, personality traits proposed by other personality theories typically appear as subsets of the FFM traits (Costa and McCrae 1992). As a result of this converging body of evidence, the FFM has achieved preeminence within scientific personality psychology.

Factor 1 of the FFM is often labeled surgency or dominance, and it is associated with variation in sociability, sensation seeking, impulsivity, attraction to reward, and social dominance. Factor 2 of the FFM is agreeableness or love, and it is positively associated with variation in nurturance, warmth, empathy, and charitableness and negatively associated with cruelty. Factor 3 of the FFM is conscientiousness/behavioral inhibition, which is associated with variation in the ability to defer gratification, persevere in unpleasant tasks, pay close attention to detail, and behave in a responsible, dependable manner. Factor 4 is neuroticism, and it is associated with variation in tendencies toward being anxious, worrisome, moody, and emotionally reactive. Factor 5 is labeled openness to experience, and it is associated with variation in imaginativeness and creativity, intellectual and aesthetic interests, and broad-mindedness and unconventionality. These five factors and their associated attributes are summarized in Table 1.