Aaron W. Lukaszewski

The Origins of Extraversion: Joint Effects of Facultative Calibration and Genetic Polymorphism

The origins of variation in extraversion are largely mysterious. Recent theories and some findings suggest that personality variation can be orchestrated by specific genetic polymorphisms. Few studies, however, have examined an alternative hypothesis that personality traits are facultatively calibrated to variations in other phenotypic features, and none have considered how these distinct processes may interact in personality determination. Since physical strength and physical attractiveness likely predicted the reproductive payoffs of extraverted behavioral strategies over most of human history, it was theorized that extraversion is calibrated to variation in these characteristics. Confirming these predicted patterns, strength and attractiveness together explained a surprisingly large fraction of variance in extraversion across two studies— effects that were independent of variance explained by an androgen receptor gene polymorphism. These novel findings initially support an integrative model wherein facultative calibration and specific genetic polymorphisms operate in concert to determine personality variation.

Androgen receptor gene sequence and basal cortisol concentrations predict men's hormonal responses to potential mates

Exposure to potential mates triggers rapid elevations of testosterone and glucocorticoid concentrations in males of many non-human species, and preliminary studies support similar effects in human males. The human studies have all reported large individual differences in these responses, however, and the present study tested whether specific biological variables may help explain these differences. Replicating past research, the present study found that mens salivary testosterone and cortisol concentrations increased after a brief conversation with a young woman, but did not change (or slightly decreased) after a conversation with a young man. In addition, smaller numbers of CAG repeats in mens androgen receptor gene, and lower baseline cortisol concentrations, each predicted larger testosterone responses to the interactions with women. The CAG repeat finding demonstrates that a specific genetic polymorphism predicts physiological responses to social interactions that may in turn have important downstream consequences on mens mating behaviour. The effects of cortisol are consistent with past demonstrations of glucocorticoid inhibition of testosterone production and show that such inhibition also affects testosterone responses to social stimuli. In sum, the present study both confirms mens hormonal reactions to potential mates and identifies novel biological variables that predict individual differences in these responses.

Testing an Adaptationist Theory of Trait Covariation: Relative Bargaining Power as a Common Calibrator of an Interpersonal Syndrome

This article provides the first test of an adaptationist ‘common calibration’ theory to explain the origins of trait covariation, which holds that (i) personality traits are often facultatively calibrated in response to cues that ancestrally predicted the reproductive payoffs of different trait levels and (ii) distinct traits that are calibrated on the basis of common input cues will exhibit consistent patterns of covariation. This theory is applied to explain the covariation within a ‘personality syndrome’ encompassing various interpersonal trait dimensions (e.g. extraversion, emotionality and attachment styles). Specifically, it is hypothesized that these traits are inter–correlated because each is calibrated in response to relative bargaining power (RBP)—a joint function of ones ability to benefit others and harm others. Path analyses from a correlational study compellingly supported this theoretical model: Objective and self–perceived measures of RBP–enhancing phenotypic features (physical attractiveness and physical strength) influenced an internal regulatory variable indexing RBP (i.e. self–perceived RBP), which in turn had robust effects on each of the focal personality traits. Moreover, in support of the theorys core postulate, controlling for self–perceived RBP greatly reduced the covariation within the interpersonal syndrome. These novel findings illustrate the promise of an evolutionary psychological approach to elucidating trait covariation. Copyright

What Explains Personality Covariation? A Test of the Socioecological Complexity Hypothesis

Correlations among distinct behaviors are foundational to personality science, but the field remains far from a consensus regarding the causes of such covariation. We advance a novel explanation for personality covariation, which views trait covariance as being shaped within a particular socioecology. We hypothesize that the degree of personality covariation observed within a society will be inversely related to the society’s socioecological complexity, that is, its diversity of social and occupational niches. Using personality survey data from participant samples in 55 nations (N = 17,637), we demonstrate that the Big Five dimensions are more strongly intercorrelated in less complex societies, where the complexity is indexed by nation-level measures of economic development, urbanization, and sectoral diversity. This inverse relationship is robust to control variables accounting for a number of methodological and response biases. Our findings support the socioecological complexity hypothesis and more generally bolster functionalist accounts of trait covariation.