Research & Publications
Sexual Exploitability and Individual Differences
Individual Differences and the Family
Friendship and Individual Differences
Personality psychology has identified and described important individual differences and made major progress toward trait taxonomy. Nonetheless, the causal origins of personality traits are not fully understood. My research objective is to apply a novel theoretical framework to the study of the psychological processes captured in personality traits to increase our understanding of their evolutionary, genetic, endocrinological, morphological, developmental, and social origins. My research program bridges four important disciplines: personality psychology with its focus on stable individual differences, social psychology with its emphasis on personal relationships, behavior genetics with its focus on heritable and environmental causal influences, and evolutionary psychology with its focus on humans’ evolved psychological mechanisms. By bringing these branches of knowledge together, my research offers a new interdisciplinary paradigm for investigating personality traits as evolved solutions to distinct social problems.
My dissertation research reveals previously unknown biological and social causes of individual differences in personality. The dissertation explores how individuals’ genes influence their social environments, and how this link between genes and social environment mediates the relationship between genetics and personality. I test the broad hypothesis that evolved psychological mechanisms produce neuroticism as an adaptive response to exclusion from social relationships. Specifically, I propose that individuals who possess fewer phenotypic indicators of genetic quality are treated as less desirable social partners and disproportionately experience social exclusion. Consequently, they exhibit elevated neuroticism that guides their attention toward negative potential social outcomes, cognitively and affectively mobilizing them to protect their limited social opportunities. I employ methods and analytical tools from multiple disciplines to provide a more comprehensive understanding of the causal pathways between genetics and personality. In the dissertation, for example, I conduct fragment analysis at the androgen receptor gene, a polymorphic locus associated with the development of desired secondary sexual characteristics and sensitivity to testosterone. I also assay salivary testosterone, an androgen that may serve as an endocrinological marker of underlying genetic quality. I collect kinetic indices of physical health and strength using a hydraulic dynamometer; assess morphological indicators of mutation load with medical grade calipers and NIH image analysis software; and administer psychometrically validated instruments.
Data from a large sample of couples in long-term relationships support the dissertation’s main hypothesis in three distinct substudies. In the first substudy, I demonstrate that individuals’ desirability as a relationship partner predicts their experience of social exclusion, which in turn predicts their neuroticism. In the second substudy, I show that men’s sexual jealousy and neuroticism adaptively adjust according to their desirability as a relationship partner and the threat of exclusion from relationships. As hypothesized, men’s relationship desirability predicts their anxiety about their partners’ fidelity as well as their own frequency of mate guarding behavior. Third, I demonstrate that exposing men to scenarios describing their mates’ certain fidelity, uncertain fidelity, and certain infidelity leads to individual differences in manifest neuroticism that directly correspond to the degree of relationship threat. Critical to the support of the main hypothesis, individual differences in desirability do not predict men’s neuroticism in response to certain fidelity or infidelity, but their desirability does predict their neuroticism when they cannot be certain of their mates’ fidelity. These findings suggest that evolved psychological mechanisms adaptively produce individual differences in neuroticism.
Results from both my dissertation and previously published research suggest that investigating individual differences through a multidisciplinary theoretical lens illuminates previously unknown causal pathways that lead to personality traits.