Applying an adaptationist framework to personality science: jealousy as a mechanistic basis of Emotionality

Over the past half century, the field of personality psychology has developed several descriptive taxonomies, but progress toward a genuinely explanatory framework for between- and within-person variation in psychology and behavior has been elusive. We argue that this is largely due to (1) neglecting a key distinction between personality traits and the underlying psychological mechanisms that generate the behaviors captured by those trait constructs, and (2) insufficient focus on attempting to explain variation in the operation of those mechanisms. Here, we illustrate the utility of a mechanism-centered approach for personality psychology by empirically demonstrating that variation in the activation of the evolved psychological mechanism of jealousy is systematically linked to HEXACO Emotionality and NEO Neuroticism. People in monogamous long-term relationships ( N = 204) read vignettes depicting varying levels of infidelity threat and wrote what they would think, feel, say, and do in response to the scenarios described. Two different groups of independent raters read the participants' written responses: one group assessed the activation of participants' jealousy by rating their expressed jealousy levels, and the other completed observer reports of the participants' HEXACO Emotionality. As predicted, (1) as infidelity threat increased across scenarios, jealousy levels increased, and (2) increased jealousy predicted higher observer-reported Emotionality. Moreover, (3) participants who exhibited higher jealousy levels reported higher levels of NEO Neuroticism, (4) these self-reports of Neuroticism covaried with the observer reports of Emotionality, and (5) a common-cause model revealed that jealousy accounted for a significant proportion of this covariance between self-reported Neuroticism and observer-reported Emotionality. These findings support the hypothesis that jealousy is a central mechanism underlying variation in Emotionality (and the overlapping Big Five/FFM dimension Neuroticism). More broadly, the present findings suggest that an understanding of specific evolved psychological mechanisms, including both their species-typical design features and individual differences in their operation, can help explain variation on major personality dimensions and offers personality science a genuine integration of universal human nature and individual differences.