Adaptationist and socioecological frameworks for personality science

Previous research suggests men are sexually attracted to women displaying cues to sexual exploitability. During human evolutionary history, men’s agreeableness, orientation towards casual sex, and relationship status may have been recurrently associated with greater net benefits of pursuing a sexually exploitative strategy. We hypothesized these three individual differences would predict men’s perceptions of women’s sexual exploitability. Seventy-two men viewed photographs of women and rated their sexual exploitability. Men’s agreeableness, sociosexual orientation, and current relationship status interacted to predict their perceptions of women’s sexual exploitability; among unmated men, the combination of low agreeableness and an orientation toward uncommitted sex was associated with higher perceptions of women’s sexual exploitability. This suggests mechanisms motivating sexually exploitative strategies may depend on an interaction between personality characteristics and situational variables.

Integrating evolutionary psychological and molecular genetic research may increase our knowledge of the psychological correlates of specific genes, as well as enhance evolutionary psychology's ability to explain individual differences. We tested the hypothesis that men's sexual jealousy mechanisms functionally calibrate their psychological output according to genetic variation at the androgen receptor locus. Mated men (N = 103) provided buccal cell samples for genotype fragment analysis and completed inventories assessing their sexually jealous cognitions and emotions. Results indicated that men with longer sequences of CAG codon repeats at the androgen receptor locus were more likely to perceive ambiguous social and environmental cues as indicative of their mates' infidelity, and experienced greater emotional upset in response to these cues. These results contribute to a growing body of research linking polymorphism at the AR locus to individual differences in psychology, and, to our knowledge, provide the first evidence pointing toward the heritability of sexual jealousy. Our discussion centers on whether the heritability of psychological differences implies direct genetic influences on the neurobiological substrate, or reflects functionally calibrated output from sex-typical and species-typical mechanisms. We conclude by describing how future research can more clearly differentiate between these alternative genetic models.

The cognitive revolution reshaped our understanding of psychology by considering the mind as an assemblage of information-processing mechanisms. A central proposition of this computational theory of mind was that, to understand human behavior, we must attend to the information-processing mechanisms responsible for producing it. Despite the indispensability of the concept of the psychological mechanism for understanding psychology, this fundamental idea remains absent from many psychologists' toolkits. We propose that a major hindrance to progress is a confusion about key terms and concepts in cognitive psychology and evolutionary biology. In this chapter, we first discuss two key terms and concepts: psychological mechanism and human nature. We then present a three-component model of a psychological mechanism and articulate key properties of evolved psychological mechanisms (EPMs), emphasizing their sensitivity to environmental inputs and their highly flexible outputs. Next, we argue that this central feature of EPMs-their variable behavioral output in response to variable environmental contexts-renders the EPM an invaluable conceptual tool for use in multiple key branches of the psychological sciences. This includes all disciplines in the psychological sciences interested in stable between-individual variation or flexible within-individual variation in response to situational influences: personality , social, developmental, and cross-cultural psychology. We conclude by outlining how the EPM concept can be readily and profitably employed in these key branches of psychology to advance the state of our science.

Pepper & Nettle use an evolutionary framework to argue that “temporal discounting” is an appropriate response to low socioeconomic status (SES), or deprivation. We suggest some conceptual refinements to their “appropriate-response” perspective, with the hope that it usefully informs future research on and public policy responses to the relationship between deprivation and temporal discounting.

The field of personality psychology offers a wealth of robust empirical research and a successful descriptive taxonomy, but neither explains the origins of the structure of human personality nor elaborates a generative framework for predicting the specific conditions that evoke the development of distinct personality traits. Exploration of traditional personality constructs within an evolutionary adaptive individual differences framework may help fill this explanatory gap. Personality traits exhibit functional features and patterns of variation expected from psychological adaptations designed to solve survival- and reproduction-related challenges recurrently faced during our species’ evolutionary history. Condition- dependent evolutionary models of personality have been proposed for decades, but only recently have begun to see empirical investigation. These models posit that species-typical psychological mechanisms take as input cues from the individual’s phenotype that would have been ancestrally linked to differential cost–benefit tradeoffs of alternative personality strategies, and produce as output personality trait levels with the greatest probabilistic net benefit for the individual. This paper elaborates a more nuanced conceptual framework that builds on earlier conceptualizations of condition-dependent traits to yield new and untested hypotheses about personality trait variation and covariation. It then describes clear future research directions for empirically investigating these readily testable hypotheses.

We argue that it is useful to distinguish between three key goals of personality science – description, prediction and explanation – and that attaining them often requires different priorities and methodological approaches. We put forward specific recommendations such as publishing findings with minimum a priori aggregation and exploring the limits of predictive models without being constrained by parsimony and intuitiveness but instead maximising out-of-sample predictive accuracy. We argue that naturally-occurring variance in many decontextualized and multi-determined constructs that interest personality scientists may not have individual causes, at least as this term is generally understood and in ways that are human-interpretable, never mind intervenable. If so, useful explanations are narratives that summarize many pieces of descriptive findings rather than models that target individual cause-effect associations. By meticulously studying specific and contextualized behaviours, thoughts, feelings and goals, however, individual causes of variance may ultimately be identifiable, although such causal explanations will likely be far more complex, phenomenon-specific and person-specific than anticipated thus far. Progress in all three areas – description, prediction, and explanation – requires higher-dimensional models than the currently-dominant “Big Few” and supplementing subjective trait-ratings with alternative sources of information such as informant-reports and behavioural measurements. Developing a new generation of psychometric tools thus provides many immediate research opportunities.

Previous research has supported adaptationist hypotheses pertaining to the functional coordination of personality strategies with phenotypic determinants of bargaining power, such as physical strength and attractiveness. However, prior studies have focused primarily on explaining variation in Extraversion and Emotionality/Neuroticism as broadband traits. The current study synthesizes data from three subject samples (N = 766) to test correlations of physical strength and attractiveness with the HEXACO factors and facets among young adults. Our analyses reveal specific, functionally meaningful, patterns of phenotypic coordination, and thereby help illuminate which facets drive previously documented associations at the factor-level. Among both sexes, strength was an especially important predictor of facets whose secondary loadings place them in the quadrant of factor space defined by high Extraversion (Expressiveness, Liveliness, Social Boldness) and low Emotionality (Fearfulness, Anxiety). Findings bolster the hypothesis that specific personality strategies are coordinated with phenotypic components of bargaining power, and suggest that granular measures of personality (such as facets) may provide more mechanistic and functional insight than broadband trait factors.

Previous research demonstrates positive associations between physical formidability and endorsement of conservative social policies entailing aggressive competition and hierarchical inequality. Similar ideological differences are associated with coalitional status. The current research extended findings by testing associations of formidability and coalitional status with individual differences in endorsement of dimensions identified by Moral Foundations Theory: "individualizing" foundations (care, fairness) and "binding" foundations (loyalty, purity, respect). Participants (N = 381) provided various measures of physical formidability and socioeconomic status before responding to the Moral Foundations Questionnaire and a militancy scale. Formidability was negatively associated with endorsing individualizing foundations, whereas socioeconomic status was positively associated with endorsing binding foundations. Formidability and socioeconomic status both positively predicted militancy. Contrary to previous research, associations emerged across men and women. Findings suggest psychological cal-culi of perceived self-interest shape political morality.

The field of personality psychology aspires to construct an overarching theory of human nature and individual differences: one that specifies the psychological mechanisms that underpin both universal and variable aspects of thought, emotion, and behaviour. Here, we argue that the adaptationist toolkit of evolutionary psychology provides a powerful meta‐theory for characterizing the psychological mechanisms that give rise to within‐person, between‐person, and cross‐cultural variations. We first outline a mechanism‐centred adaptationist framework for personality science, which makes a clear ontological distinction between (i) psychological mechanisms designed to generate behavioural decisions and (ii) heuristic trait concepts that function to perceive, describe, and influence others behaviour and reputation in everyday life. We illustrate the utility of the adaptationist framework by reporting three empirical studies. Each study supports the hypothesis that the anger programme—a putative emotional adaptation—is a behaviour‐regulating mechanism whose outputs are described in the parlance of the person description factor called ‘Agreeableness’. We conclude that the most productive way forward is to build theory‐based models of specific psychological mechanisms, including their culturally evolved design features, until they constitute a comprehensive depiction of human nature and its multifaceted variations. © 2020 European Association of Personality Psychology

Historically, psychology has been characterized by a dichotomy between branches that focus on human nature and those that focus on individual differences. Initial “grand theories” of personality, such as those advanced by Freud, Maslow, and others, were interested in universal psychological features. For Freud, the emphasis was on sexual and aggressive “instincts” and a universal sequence of psychosexual stages. For Maslow, the focus was on a hierarchy of universal psychological needs, from immediate physiological demands to “self-actualization.” Historically, personality psychology has been the primary branch that has aspired to such broad conceptualizations of human nature. Over the past few decades, personality psychology has retreated from this grand goal. Most empirical research on personality deals with individual differences, not with human nature, let alone the links between the two (e.g., McCrae & John, 1992). By focusing largely on individual differences (Larsen & Buss, 2018), modern personality psychology has implicitly ceded the study of human nature to other branches such as social psychology. Personality psychology’s restricted focus on individual differences has led some to identify this as a defining feature of the field: “that branch of psychology which is concerned with… the ways in which individuals differ from one another” (Wiggins, 1979, p. 375). Grand theories of human nature that once characterized the field are now regarded primarily as historical relics. The central argument of this chapter is that personality psychology should reclaim its grand goals, and that an evolutionary framework will be central to achieving these goals. This chapter is organized into three sections. First, we present a conceptual tool – the psychological mechanism – that dissolves the unnecessary (and often false) dichotomy between “human nature” and “individual differences”. Second, we elucidate the multiple evolutionary processes that have operated on the human mind and the different types of products that these processes yield, which include both species-typical psychological phenomena and individual differences. Finally, we offer a series of suggestions for how these tools can be incorporated into personality research. In offering these recommendations, we hope this chapter contributes to personality psychology by moving toward a more comprehensive framework that uses an understanding of evolved psychological mechanisms to explain and predict the origins of individual differences.

The hypothesis of a human-universal personality structure is undermined by cross-cultural studies in small-scale societies. To explain cross-population differences in patterns of behavioral covariance, we proposed the niche diversity hypothesis, which holds that the degree of behavioral covariation within a population is inversely related to the number and diversity of niches within its socioecology. This hypothesis is formalized as a computational model, and its predictions have been supported empirically. Herein, we respond to several important issues regarding this line of research that were raised in a recent commentary: (1) the study of specific behavioral syndromes should be integrated into the niche diversity model; (2) environmental harshness might alternatively explain our cross-cultural findings regarding effects of niche diversity; and (3) better definitions of behavioral traits are needed for future research. We conclude that the niche diversity hypothesis can be integrated with other explanations for cross-cultural differences in personality covariation.

The niche diversity hypothesis proposes that personality structure arises from the affordances of unique trait-combinations within a society. Prior tests of the hypothesis in 55 nations suffer from potential confounds associated with differences in the measurement properties of personality scales across groups. Using recently developed psychometric methods for the approximation of cross-national measurement invariance, we test the niche diversity hypothesis in a novel sample of 115 nations (N = 685,089). Niche diversity was robustly related to both inter-factor covariance and personality dimensionality but was not consistently related to intra-factor variance across nations. These findings generally bolster the core of the niche diversity hypothesis, demonstrating the contingency of human personality structure on socioecological contexts.

Objectives Life History (LH) Theory explains how organisms allocate energy among the competing demands of growth and maintenance (i.e., investment in future reproduction), mating effort, and parenting effort. LH profile is thought to be influenced by cues of extrinsic mortality and morbidity. Human LH strategies have been conceptualized on a fast-slow continuum and have been measured via biometric indicators (e.g., developmental timing) and psychometric indictors (e.g., personality traits). We aim to preliminarily develop and test an integrated model in which childhood environments are hypothesized to influence variation in psychometric LH profile in adulthood via effects on earlier biometric developmental LH indicators.Methods We tested, in a sample of 370 U.S. undergraduates, a model in which associations of early life adversity on psychometrically assessed LH profile are mediated by biometrically assessed LH indicators (e.g., developmental timing; somatic state).ResultsThe complete model was not supported. Several direct and indirect paths were consistent with theory-driven predictions, but other findings were inconsistent with LH-based hypotheses. Best fitting models differed by sex, such that an association existed between males’ psychometric LH profile and neighborhood stress, father closeness, and somatic state (telomere length), whereas an association existed between females’ developmental timing with adult LH profile and father closeness.Conclusions While there was limited support for the complete multivariate model, we conclude that an integrative approach to the assessment and modeling of LH variation holds substantial promise for future research.

Life history theory is a fruitful source of testable hypotheses about human individual differences. However, this field of study is beset by unresolved debates about basic concepts and methods. One of these controversies concerns the usefulness of instruments that purport to tap a unidimensional life history (LH) factor based on a set of self-reported personality, social, and attitudinal variables. Here, we take a novel approach to analyzing the psychometrics of two variants of the Arizona Life History Battery: the Mini-K and the K-SF-42. Psychological network analysis generates models in which psychological variables (thoughts, feelings, or behaviors) comprise the nodes of a network, while partial correlation coefficients between these variables comprise the edges of the network. Centrality indices (strength, closeness, and betweenness) operationalize each node's importance, based on the pattern of the connections in which that node plays a role. Because childhood environments are hypothesized to influence adult LH, we tested the hypothesis that among the Mini-K items, and the K-SF-42 scales, those that tap relationships with parents are central to the networks (pairwise Markov random fields) constructed from these instruments. In an MTurk sample and an undergraduate sample that completed the Mini-K, and an MTurk sample that completed the K-SF-42, this hypothesis was falsified. Indeed, the relationships with parents items were among the most peripheral in all three networks. We propose that network analysis, as an alternative to latent variable modeling, offers considerable potential to test hypotheses about the input-output mappings of specific evolved psychological mechanisms.

Mate choice lies close to differential reproduction, the engine of evolution. Patterns of mate choice consequently have power to direct the course of evolution. Here we provide evidence suggesting one pattern of human mate choice—the tendency for mates to be similar in overall desirability—caused the evolution of a structure of correlations that we call the d factor. We use agent-based models to demonstrate that assortative mating causes the evolution of a positive manifold of desirability, d, such that an individual who is desirable as a mate along any one dimension tends to be desirable across all other dimensions. Further, we use a large cross-cultural sample with n = 14,478 from 45 countries around the world to show that this d-factor emerges in human samples, is a cross-cultural universal, and is patterned in a way consistent with an evolutionary history of assortative mating. Our results suggest that assortative mating can explain the evolution of a broad structure of human trait covariation.

Evolutionary theory is the organizing framework for the life sciences because of its unique value in deriving falsifiable predictions about the causal structure of organisms. This paper outlines the relationships of evolutionary principles to the study of phenotypic variation and defines two distinct paradigms for personality science. The first of these, dimensional cost-benefit analysis (DCBA), entails analyzing the reproductive cost-benefit tradeoffs along inductively derived personality dimensions (e.g., the big five) to derive predictions regarding adaptively-patterned variation in manifest trait levels. The second paradigm, ground-up adaptationism (GUA), requires building models of specific psychological mechanisms, from the ground-up, including their variable parameters that result in manifest behavioral variation. After evaluating the strengths and limitations of these paradigms, it is concluded that (1) inductively derived dimensions of person description should not serve as the field’s explanatory targets; (2) GUA represents the most powerful available framework for elucidating the psychological mechanisms which comprise human nature and produce its diverse range of behavioral variants; and (3) the goals of adaptationist evolutionary psychology are the same as those guiding personality psychology’s next era: to identify the mechanisms that comprise the mind, figure out how they work, and determine how they generate behavioral variation.

The structure of personality refers to the covariation among specific behavioral patterns in a population. Statistically derived models of personality-such as the Big Five or HEXACO models-usually assume that the covariance structure of personality characteristics is a human universal. Cross-cultural studies, however, have challenged this view, finding that less complex societies exhibit stronger covariation among behavioral characteristics, resulting in fewer derived personality factors. To explain these results, we propose the niche diversity hypothesis, which predicts that a greater diversity of social and ecological niches elicits a more diverse set of multivariate behavioral profiles, and hence lower trait covariance, at the population level. We formalize this hypothesis as a computational model in which individuals assort into niches, which influence their behavioral traits. We find that the model provides strong support for the niche diversity hypothesis and reproduces empirical results from recent cross-cultural studies. This work provides a general explanation for differences in personality structure between populations in both humans and other animals, and also produces several new empirical predictions. It also suggests a radical reimagining of personality trait research: instead of reifying statistical descriptions of manifest personality structures, research should focus more attention on modeling their underlying causes.

Recent research has linked men’s facial width-to-height ratio (fWHR) to perceptions of aggressiveness, dominance and untrustworthiness, as well aggressive and exploitative behavior, leading to speculation that a wide face may be an indicator of an intrasexually-competitive behavioral strategy. Not understood, however, are the physiological mechanisms that produce fWHR variance and explain the link between fWHR and behavior. Several researchers have suggested that fWHR variance may be related to the number of CAG repeats in the androgen receptor gene (CAGn) – a polymorphism that regulates sensitivity to androgens – either directly or through an interaction with testosterone concentrations. We tested this hypothesis, and found that CAGn did not predict fWHR variance, either directly or by moderating the effect of testosterone concentrations. Furthermore, we found that fWHR did not predict baseline testosterone or testosterone reactivity in our full sample, but did predict baseline testosterone among our white participants. We discuss these results in relation to previous research on fWHR and testosterone, and suggest new mechanisms that may explain fWHR variation.

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 ¼ 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.

Evolutionary theories of personality origins have stimulated much empirical research in recent years, but pertinent data from small-scale human societies have been in short supply. We investigate adaptively patterned personality variation among Tsimane’ forager-horticulturalists. Based on a consideration of cost-benefit tradeoffs that likely maintain variation in human prosociality, we hypothesize that individual differences in prosocial personality traits are facultatively calibrated to variation in “embodied capital”—that is, knowledge, skills, or somatic traits that increase expected future fitness. In support of this hypothesis, 2 components of embodied capital—physical strength and formal education—associated positively with Tsimane’ prosocial leadership orientation (PLO), a broad personality dimension representing gregarious cooperation, interpersonal warmth, and pursuit of leadership. Moreover, using pedigrees to compute heritability estimates, strength and education had additive effects on the heritable variance in PLO, which suggests that prosocial traits may be “reactively heritable” by virtue of their calibration to condition-dependent components of embodied capital. Although alternative explanations must be falsified in future research, our findings 1) provide one of the first demonstrations of adaptively patterned personality variation in a small-scale society and 2) illustrate the potential power of an adaptationist approach to elucidate the causal underpinnings of heritable personality variation.

Extant research supports the hypothesis that bio-metric indicators of life history (LH) strategy, such as the timing of sexual debut, are calibrated in response to cues sampled early in development (before age 7). Herein, we theorize that the experience of sexual debut itself may further calibrate women's LH-related behavioral phenotypes across adolescence by modulating subsequent investment in mating effort, which is associated with faster (vs. slower) LH speed. We tested this hypothesis using longitudinal data, which included Q-Sort LH scores at ages 14, 18, and 23, and a report of whether or not sexual debut occurred between ages 14 and 18. Results demonstrated that women (but not men) who experienced their sexual debut between the ages of 14 and 18 showed greater relative acceleration of LH speed during this period than women who had not debuted by age 18. However, these same effects had weakened by age 23—which underscores the broader idea that LH-related behavioral phenotypes exhibit substantial cue-based plasticity across adolescence and into adulthood. Although alternative explanations for the observed patterns remain unfalsified, these findings are consistent with the hypothesis that developmental LH trajectory is regulated in relation to the timing of sexual debut in adolescence. This possibility could be further investigated in future research.

Human life history (LH) strategies are theoretically regulated by developmental exposure to environmental cues that ancestrally predicted LH-relevant world states (e.g., risk of morbidity–mortality). Recent modeling work has raised the question of whether the association of childhood family factors with adult LH variation arises via (i) direct sampling of external environmental cues during development and/or (ii) calibration of LH strategies to internal somatic condition (i.e., health), which itself reflects exposure to variably favorable environments. The present research tested between these possibilities through three online surveys involving a total of over 26,000 participants. Participants completed questionnaires assessing components of self-reported environmental harshness (i.e., socioeconomic status, family neglect, and neighborhood crime), health status, and various LH-related psychological and behavioral phenotypes (e.g., mating strategies, paranoia, and anxiety), modeled as a unidimensional latent variable. Structural equation models suggested that exposure to harsh ecologies had direct effects on latent LH strategy as well as indirect effects on latent LH strategy mediated via health status. These findings suggest that human LH strategies may be calibrated to both external and internal cues and that such calibrational effects manifest in a wide range of psychological and behavioral phenotypes.