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Chen Y, Ge E, Zhou L, Du J, Mace R. Gender inequality in workloads explained by operational sex ratio. iScience 2024; 27:110063. [PMID: 38883828 PMCID: PMC11179575 DOI: 10.1016/j.isci.2024.110063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 03/16/2024] [Accepted: 05/17/2024] [Indexed: 06/18/2024] Open
Abstract
Ecological differences between human populations can affect the relative strength of sexual selection, and hence drive gender inequality. Here, we exploit the cultural diversity of southwestern China, where some village sex ratios are female-biased, in part due to a proportion of males entering monastic celibacy, to evaluate the role of sex ratio on the sexual division of labor. We used a detachable activity tracker to measure workload by step counts in both sexes among 561 individuals in 55 villages in six different areas. We show that a lower sex ratio and a higher prevalence of monasticism are associated with higher women's workloads and reduced men's workloads in the non-celibate population. As the operational sex ratio increases, gender inequality diminishes. This study offers valuable insights into the origins of gender disparities by examining the role of sex ratio on the sexual division of labor.
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Affiliation(s)
- Yuan Chen
- Department of Anthropology, University College London, 14 Taviton Street, WC1H 0BW London, UK
- State Key Laboratory of Grassland and Agro-Ecosystems, College of Ecology, Lanzhou University, 222 Tianshui South Road, Lanzhou, Gansu Province 730000, P.R. China
| | - Erhao Ge
- Department of Anthropology, University College London, 14 Taviton Street, WC1H 0BW London, UK
- State Key Laboratory of Grassland and Agro-Ecosystems, College of Ecology, Lanzhou University, 222 Tianshui South Road, Lanzhou, Gansu Province 730000, P.R. China
| | - Liqiong Zhou
- State Key Laboratory of Grassland and Agro-Ecosystems, College of Ecology, Lanzhou University, 222 Tianshui South Road, Lanzhou, Gansu Province 730000, P.R. China
| | - Juan Du
- Department of Anthropology, University College London, 14 Taviton Street, WC1H 0BW London, UK
- State Key Laboratory of Grassland and Agro-Ecosystems, College of Ecology, Lanzhou University, 222 Tianshui South Road, Lanzhou, Gansu Province 730000, P.R. China
| | - Ruth Mace
- Department of Anthropology, University College London, 14 Taviton Street, WC1H 0BW London, UK
- Institute for Advanced Study in Toulouse, Université de Toulouse 1 Capitole, France
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2
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Bshary R, Noë R. A marine cleaning mutualism provides new insights in biological market dynamics. Philos Trans R Soc Lond B Biol Sci 2023; 378:20210501. [PMID: 36934753 PMCID: PMC10024986 DOI: 10.1098/rstb.2021.0501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2022] [Accepted: 01/22/2023] [Indexed: 03/21/2023] Open
Abstract
Most mutually beneficial social interactions (cooperation within species, mutualism between species) involve some degree of partner choice. In an analogy to economic theory as applied to human trading practices, biological market theory (BMT) focuses on how partner choice affects payoff distributions among non-human traders. BMT has inspired a great diversity of research, including research on the mutualism between cleaner fish Labroides dimidiatus and other marine fish, their 'clients'. In this mutualism, clients have ectoparasites removed and cleaners obtain food in return. We use the available data on L. dimidiatus cleaner-client interactions to identify avenues for future expansion of BMT. We focus on three main topics, namely how partner quality interacts with supply-to-demand ratios to affect service quality, the role of threats and forms of forceful intervention, and the potential role of cognition. We consider it essential to identify the specifics of each biological market as a basis for the development of more sophisticated BMT models. This article is part of the theme issue 'Half a century of evolutionary games: a synthesis of theory, application and future directions'.
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Affiliation(s)
- Redouan Bshary
- Institute of Biology, University of Neuchâtel, Emile-Argand 11, 2000 Neuchâtel, Switzerland
| | - Ronald Noë
- Department of Psychology, Tuk, The Netherlands and Arizona State University, Tempe, AZ 85287-1104, USA
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3
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Kappeler PM, Benhaiem S, Fichtel C, Fromhage L, Höner OP, Jennions MD, Kaiser S, Krüger O, Schneider JM, Tuni C, van Schaik J, Goymann W. Sex roles and sex ratios in animals. Biol Rev Camb Philos Soc 2023; 98:462-480. [PMID: 36307924 DOI: 10.1111/brv.12915] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 10/12/2022] [Accepted: 10/14/2022] [Indexed: 11/29/2022]
Abstract
In species with separate sexes, females and males often differ in their morphology, physiology and behaviour. Such sex-specific traits are functionally linked to variation in reproductive competition, mate choice and parental care, which have all been linked to sex roles. At the 150th anniversary of Darwin's theory on sexual selection, the question of why patterns of sex roles vary within and across species remains a key topic in behavioural and evolutionary ecology. New theoretical, experimental and comparative evidence suggests that variation in the adult sex ratio (ASR) is a key driver of variation in sex roles. Here, we first define and discuss the historical emergence of the sex role concept, including recent criticisms and rebuttals. Second, we review the various sex ratios with a focus on ASR, and explore its theoretical links to sex roles. Third, we explore the causes, and especially the consequences, of biased ASRs, focusing on the results of correlational and experimental studies of the effect of ASR variation on mate choice, sexual conflict, parental care and mating systems, social behaviour, hormone physiology and fitness. We present evidence that animals in diverse societies are sensitive to variation in local ASR, even on short timescales, and propose explanations for conflicting results. We conclude with an overview of open questions in this field integrating demography, life history and behaviour.
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Affiliation(s)
- Peter M Kappeler
- Behavioral Ecology and Sociobiology Unit, German Primate Center - Leibniz Institute of Primatology, Kellnerweg 4, 37077, Göttingen, Germany
- Department of Sociobiology/Anthropology, University of Göttingen, Kellnerweg 6, 37077, Göttingen, Germany
| | - Sarah Benhaiem
- Department of Ecological Dynamics, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Strasse 17, D-10315, Berlin, Germany
| | - Claudia Fichtel
- Behavioral Ecology and Sociobiology Unit, German Primate Center - Leibniz Institute of Primatology, Kellnerweg 4, 37077, Göttingen, Germany
| | - Lutz Fromhage
- Department of Biological and Environmental Science, Ambiotica, University of Jyväskylä, PO Box 35, 40014, Jyväskylä, Finland
| | - Oliver P Höner
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Strasse 17, D-10315, Berlin, Germany
| | - Michael D Jennions
- Division of Ecology & Evolution, Research School of Biology, ANU College of Science, The Australian National University, RN Robertson Building, 46 Sullivans Creek Road, Canberra, ACT, 2600, Australia
| | - Sylvia Kaiser
- Department of Behavioural Biology, University of Münster, Badestr. 13, 48149, Münster, Germany
| | - Oliver Krüger
- Department of Animal Behavior, Bielefeld University, Morgenbreede 45, 33615, Bielefeld, Germany
| | - Jutta M Schneider
- Department of Biology, Institute of Zoology, Universität Hamburg, Martin-Luther-King Platz 3, 20146, Hamburg, Germany
| | - Cristina Tuni
- Department of Biology II, Ludwig Maximilians University of Munich, Großhaderner Str 2, 82152, Planegg-Martinsried, Germany
| | - Jaap van Schaik
- Applied Zoology and Nature Conservation, University of Greifswald, Loitzer Str. 26, 17489, Greifswald, Germany
| | - Wolfgang Goymann
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Eberhard-Gwinner-Str. 6a, D-82319, Seewiesen, Germany
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4
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Luberti FR, Blake KR, Brooks RC. Widespread Promiscuity and Cheap Weddings: Can "Low-Value" Sexual Relationships Make Certain Individuals More Sexually Conservative? ARCHIVES OF SEXUAL BEHAVIOR 2022; 51:2791-2811. [PMID: 35552934 DOI: 10.1007/s10508-021-02216-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 11/02/2021] [Accepted: 11/03/2021] [Indexed: 06/15/2023]
Abstract
Attitudes toward sexual relationships can have evolutionary underpinnings because these attitudes often serve, or at least reflect, the attitude holder's mating self-interest. Sexually restricted individuals, for example, hold conservative attitudes toward same-sex and opposite-sex sexual relationships because conservative attitudes benefit their mating strategies (e.g., monogamy). Certain mating market cues, however, can shift attitudes. In two experiments recruiting Americans and Australians (total N = 1298), we took a data-driven approach to test whether experimental manipulations of (1) promiscuity among either homosexuals (gays and lesbians) or heterosexuals and (2) the financial amount that either homosexuals (gays and lesbians) or heterosexuals invest in weddings would shift attitudes toward same-sex marriage, dating, and romantic spending. In Experiment 1, we did not replicate previous findings that homosexual promiscuity affects attitudes to same-sex marriage, nor did we find any effects of priming heterosexual promiscuity. However, priming participants with the notion that either homosexuals or heterosexuals were highly promiscuous increased support for traditional relationship norms among sexually restricted Australian (but not American) men. This effect was smaller when we controlled for participant sexual orientation, because primes of high homosexual or heterosexual promiscuity increased support for these traditional norms in exclusively heterosexual Australians, but decreased support in non-heterosexual Australians. Experiment 2 found that American and Australian men's opposition to same-sex marriage increased when they were led to believe that either homosexual or heterosexual weddings were cheap, even when controlling for participant sexual orientation. Overall, results provide some support for the argument that mating market cues affect attitudes toward sexual relationships.
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Affiliation(s)
- Francesca R Luberti
- Evolution and Ecology Research Centre, University of New South Wales, Sydney, NSW, 2052, Australia.
- Department of Psychology, Nipissing University, Room A223-A, 100 College Drive, North Bay, ON, P1B 8L7, Canada.
| | - Khandis R Blake
- Evolution and Ecology Research Centre, University of New South Wales, Sydney, NSW, 2052, Australia
- Melbourne School of Psychological Sciences, The University of Melbourne, Melbourne, VIC, Australia
| | - Robert C Brooks
- Evolution and Ecology Research Centre, University of New South Wales, Sydney, NSW, 2052, Australia
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5
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Davidian E, Surbeck M, Lukas D, Kappeler PM, Huchard E. The eco-evolutionary landscape of power relationships between males and females. Trends Ecol Evol 2022; 37:706-718. [PMID: 35597702 DOI: 10.1016/j.tree.2022.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 04/04/2022] [Accepted: 04/06/2022] [Indexed: 11/17/2022]
Abstract
In animal societies, control over resources and reproduction is often biased towards one sex. Yet, the ecological and evolutionary underpinnings of male-female power asymmetries remain poorly understood. We outline a comprehensive framework to quantify and predict the dynamics of male-female power relationships within and across mammalian species. We show that male-female power relationships are more nuanced and flexible than previously acknowledged. We then propose that enhanced reproductive control over when and with whom to mate predicts social empowerment across ecological and evolutionary contexts. The framework explains distinct pathways to sex-biased power: coercion and male-biased dimorphism constitute a co-evolutionary highway to male power, whereas female power emerges through multiple physiological, morphological, behavioural, and socioecological pathways.
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Affiliation(s)
- Eve Davidian
- Ngorongoro Hyena Project, Ngorongoro Conservation Area, Arusha, Tanzania.
| | - Martin Surbeck
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Dieter Lukas
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Peter M Kappeler
- German Primate Center, Behavioral Ecology Unit, Leibniz Institute of Primate Biology, Göttingen, Germany; Department of Sociobiology and Anthropology, University of Göttingen, Göttingen, Germany
| | - Elise Huchard
- Anthropologie Évolutive, Institut des Sciences de l'Évolution de Montpellier (ISEM), Montpellier, France.
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Lewis RJ, Bueno GL, Di Fiore A. Variation in Female Leverage: The Influence of Kinship and Market Effects on the Extent of Female Power Over Males in Verreaux’s Sifaka. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.851880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Female mammals employ reproductive strategies (e.g., internal gestation) that result in power asymmetries specific to intersexual dyads. Because the number of eggs available for fertilization at any given time for most mammals is quite limited, having a fertilizable egg is potentially an important source of economic power for females. Control over mating opportunities is a source of intersexual leverage for female Verreaux’s sifaka (Propithecus verreauxi). We examined economic factors thought to influence the value of mating opportunities, and, thus, the extent of female leverage: kinship and market effects. Using a longitudinal dataset of agonistic interactions collected during focal animal sampling of all adult individuals in 10 social groups from 2008 to 2019, we tested the effects of relatedness, female parity, reproductive season, and adult sex ratio (population and group) on (1) the direction of submissive signaling and (2) which sex won a contested resource. While 96% of the acts of submission were directed from males toward females, females only won a third of their conflicts with males. Thus, our study has implications for evolutionary explanations of female-biased power. If female power evolved due to their greater need for food and other resources, then intersexual conflicts would be expected to result in males more consistently relinquishing control of resources. As expected, males were more likely to chatter submissively toward successful mothers, during the mating season, and when the sex ratio was male-biased. Although females generally had less power to win a conflict when their fertilizable egg was less valuable (when they were nulliparous or unsuccessful mothers or when interacting with male kin) and with an increasing female-bias in the sex ratio, this ability to win additionally was influenced by which sex initiated the conflict. Our study demonstrates that female leverage can be influenced by the supply and demand for mating opportunities, but evoking submission does not translate into winning a resource. Indeed, intersexual power is dynamic, contextual, and dependent on the individuals in the dyad.
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Prall S, Scelza B. The effect of mating market dynamics on partner preference and relationship quality among Himba pastoralists. SCIENCE ADVANCES 2022; 8:eabm5629. [PMID: 35507659 PMCID: PMC9067927 DOI: 10.1126/sciadv.abm5629] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Accepted: 03/16/2022] [Indexed: 06/14/2023]
Abstract
Relative mate value has long been believed to be a critical component of mate choice in humans. However, most empirical work focuses on preferences rather than actual pair formation, and data connecting partner preferences, partnership formation, and relationship quality remain rare. Here, we estimate mate value using >12,000 ratings by opposite-sex, in-group members to understand both hypothetical partnership preferences and actualized relationship dynamics. When evaluating hypothetical partnerships, people generally prefer individuals whose mate value is higher than their own, indicating an aspirational matching strategy. However, mate value comparisons of individuals in marital and nonmarital relationships show a positive correlation, suggesting that individuals tend to pair up with similarly desirable individuals. Furthermore, despite aspirational preferences, couples who are more closely matched reported greater relationship quality, measured through frequency of interactions, reported sexual histories, and partnership length.
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Affiliation(s)
- Sean Prall
- Department of Anthropology, University of Missouri, Columbia, MO, USA
| | - Brooke Scelza
- Department of Anthropology, University of California, Los Angeles, Los Angeles, CA, USA
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8
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Changes in Positive Affect Due to Popularity in an Experimental Dating Context Influence Some of Men’s, but Not Women’s, Socio-Political Attitudes. ADAPTIVE HUMAN BEHAVIOR AND PHYSIOLOGY 2022. [DOI: 10.1007/s40750-022-00188-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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9
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Triki Z, Richter XYL, Demairé C, Kurokawa S, Bshary R. Marine cleaning mutualism defies standard logic of supply and demand. Am Nat 2021; 199:455-467. [DOI: 10.1086/718315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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11
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Filser A, Barclay K, Beckley A, Uggla C, Schnettler S. Are skewed sex ratios associated with violent crime? A longitudinal analysis using Swedish register data. EVOL HUM BEHAV 2021. [DOI: 10.1016/j.evolhumbehav.2020.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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12
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Castro FN, Hattori WT, Gaulin SJC, Yamamoto ME, Lopes FDA. Male Mating Expectations in Brazilian and American Samples. Front Psychol 2021; 12:617754. [PMID: 33643146 PMCID: PMC7902785 DOI: 10.3389/fpsyg.2021.617754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 01/20/2021] [Indexed: 11/13/2022] Open
Abstract
This study aims to investigate assortative mating based on mate value from male perspective. Male participants (132 Brazilian and 106 American) evaluated hypothetical “stimulus” males described in terms of physical attractiveness, social skills, and social status (each varied in high or low levels). Participants rated each stimulus and each stimulus' preferred mating partner on nine traits. The results showed that (1) positive assortative mating was expected in romantic relationships; (2) the stimulus ratings did not vary independently, suggesting that mate value is the result of the interaction of the characteristics of individuals; and (3) that participants expected physically attractive and healthier female partners to pair with high-status male stimuli. The American and Brazilian mating expectations were similar, minor differences indicate that Brazilian participants considered men with high levels of social skills to be more ambitious and intelligent; American participants expected men of high status to be healthier; Brazilians expect men of high status to have more attractive faces, while Americans expected these men to possess more attractive bodies; and Brazilian participants assigned more attractive bodies to men of lower status. These differences reflect the influence of economic and cultural factors on the local environment. The study contributes to the understanding of the construction of market value and reveals that male expectations are in line with human mating preferences. The investigation of mating expectations can be a rich approach to investigate socio-cultural aspects that are related to mating in different cultures
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Affiliation(s)
- Felipe Nalon Castro
- Human Behavior Evolution Laboratory, Psychobiology Postgraduate Program, Department of Physiology and Behavior, Federal University of Rio Grande do Norte, Natal, Brazil
| | - Wallisen Tadashi Hattori
- Department of Public Health, Faculty of Medicine, Federal University of Uberlândia, Uberlândia, Brazil
| | - Steven J C Gaulin
- Department of Anthropology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Maria Emília Yamamoto
- Human Behavior Evolution Laboratory, Psychobiology Postgraduate Program, Department of Physiology and Behavior, Federal University of Rio Grande do Norte, Natal, Brazil
| | - Fívia de Araújo Lopes
- Human Behavior Evolution Laboratory, Psychobiology Postgraduate Program, Department of Physiology and Behavior, Federal University of Rio Grande do Norte, Natal, Brazil
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Broadening horizons: Sample diversity and socioecological theory are essential to the future of psychological science. Proc Natl Acad Sci U S A 2019; 115:11420-11427. [PMID: 30397108 DOI: 10.1073/pnas.1720433115] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The present lack of sample diversity and ecological theory in psychological science fundamentally limits generalizability and obstructs scientific progress. A focus on the role of socioecology in shaping the evolution of morphology, physiology, and behavior has not yet been widely applied toward psychology. To date, evolutionary approaches to psychology have focused more on finding universals than explaining variability. However, contrasts between small-scale, kin-based rural subsistence societies and large-scale urban, market-based populations, have not been well appreciated. Nor has the variability within high-income countries, or the socioeconomic and cultural transformations affecting even the most remote tribal populations today. Elucidating the causes and effects of such broad changes on psychology and behavior is a fundamental concern of the social sciences; expanding study participants beyond students and other convenience samples is necessary to improve understanding of flexible psychological reaction norms among and within populations. Here I highlight two examples demonstrating how socioecological variability can help explain psychological trait expression: (i) the role of environmental harshness and unpredictability on shaping time preference and related traits, such as impulsivity, vigilance, and self-efficacy; and (ii) the effects of industrialization, market integration, and niche complexity on personality structure. These cases illustrate how appropriate theory can be a powerful tool to help determine choices of diverse study populations and improve the social sciences.
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