The pandemic exposes human nature: 10 evolutionary insights

The pandemic exposes human nature: 10 evolutionary insights. Benjamin M. Seitz, Athena Aktipis, David M. Buss, Joe Alcock, Paul Bloom,  Michele Gelfand, Sam Harris,  Debra Lieberman, Barbara N. Horowitz,  Steven Pinker,  David Sloan Wilson, and Martie G. Haselton. PNAS November 10, 2020 117 (45) 27767-27776; first published October 22, 2020; https://doi.org/10.1073/pnas.2009787117

Abstract: Humans and viruses have been coevolving for millennia. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, the virus that causes COVID-19) has been particularly successful in evading our evolved defenses. The outcome has been tragic—across the globe, millions have been sickened and hundreds of thousands have died. Moreover, the quarantine has radically changed the structure of our lives, with devastating social and economic consequences that are likely to unfold for years. An evolutionary perspective can help us understand the progression and consequences of the pandemic. Here, a diverse group of scientists, with expertise from evolutionary medicine to cultural evolution, provide insights about the pandemic and its aftermath. At the most granular level, we consider how viruses might affect social behavior, and how quarantine, ironically, could make us susceptible to other maladies, due to a lack of microbial exposure. At the psychological level, we describe the ways in which the pandemic can affect mating behavior, cooperation (or the lack thereof), and gender norms, and how we can use disgust to better activate native “behavioral immunity” to combat disease spread. At the cultural level, we describe shifting cultural norms and how we might harness them to better combat disease and the negative social consequences of the pandemic. These insights can be used to craft solutions to problems produced by the pandemic and to lay the groundwork for a scientific agenda to capture and understand what has become, in effect, a worldwide social experiment.

Keywords: COVID-19evolutionevolutionary medicineevolutionary psychologycultural evolution

Insight 1: The Virus Might Alter Host Sociability

Insight 2: “Generation Quarantine” May Lack Critical Microbial Exposures

Insight 3: Activating Disgust Can Help Combat Disease Spread

Insight 4: The Mating Landscape Is Changing, and There Will Be Economic Consequences from a Decrease in Birth Rates

Insight 5: Gender Norms Are Backsliding, and Gender Inequality Is Increasing

Insight 6: An Increase in Empathy and Compassion Is Not Guaranteed

Insight 7: We Have Not Evolved to Seek the Truth

Insight 8: Combating the Pandemic Requires Its Own Evolutionary Process

Insight 9: Cultural Evolutionary Forces Impact COVID-19 Severity

Insight 10: Human Progress Continues

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Insight 7: We Have Not Evolved to Seek the Truth

Humans evolved in small groups under threat of starvation, predation, and exploitation by outsiders—and generally lived brief lives, favoring short-term strategies for consuming resources that could support successful reproduction (59). We have not evolved to think clearly about long-term threats like pandemics—which are statistically abstract and global. And yet, for at least a century, we’ve understood that the threat of a deadly pandemic is real and ever present (60). How should we have responded to this knowledge?

We should have prepared for the next pandemic in advance. But, to do this, we would have had to feel the need to prepare—and been willing to incur actual costs in the face of what could have seemed, in the absence of dead and dying people, like nothing more than morbid speculation.

Unfortunately, most of us are terrible at weighing risks presented as abstract probabilities (61). We also heavily discount the well-being of our future selves (62), along with that of distant strangers (63) and future generations (64), and in ways that are both psychologically strange and, in a modern environment, ethically indefensible. We’re highly susceptible to conspiracy thinking (65), and display an impressive capacity to deceive ourselves, before doing the hard work of deceiving others (66). These predispositions likely endowed our ancestors with advantages (67, 68), but they also suggest that our species is not wired for seeking a precise understanding of the world as it actually is.

Thus, our conversation about most things tends to be a tissue of false certainties and unhedged bets. We look for evidence to support our current beliefs, while ignoring the rest (69). When we encounter friends or family in thrall to some fresh piece of misinformation, we often lack the courage to correct them. Meanwhile, behind a screen of anonymity, we eagerly confront the views of complete strangers online. Paradoxically, the former circumstance presents an opportunity to actually change opinion, while the latter is more likely to further entrench people in their misinformed views (70). Although these predispositions did not cause SARS-CoV-2 to first enter the human population, they are, at least in part, responsible for the pandemic that ensued.

Scientific Agenda.

Evaluate methods to combat shortcomings in reasoning due to mismatches between the demands of the ancestral past and the present, conspiracy thinking, and the spread of misinformation, both in face-to-face communication and on social networks, particularly as they relate to the pandemic and health-relevant information.

In 2000, the rate of being on probation was 1.6x higher & the rate of being parole was 3.6x higher for Hispanics than non-Hispanic whites; in 2016, the probation disparity had disappeared and the parole disparity had shrunk by 85%

The rapidly shifting Hispanic experience of American criminal justice: Vanishing disparities in jail, probation, and parole rates — rising levels of law enforcement employment. Keith Humphreys. Aug 28 2021. https://www.slowboring.com/p/hispanic-prison

Excerpts:

An otherwise dull new government report [to download go to https://www.slowboring.com/p/hispanic-prison] on incarceration contains a startling fact: Hispanics are slightly less likely to be jailed than whites. It’s one of multiple unappreciated signs of fading disparities between Hispanics and non-Hispanic whites in the criminal justice system, a phenomenon with substantial implications both for the future of reform and electoral politics.

[chart at https://www.slowboring.com/p/hispanic-prison]

This isn’t just about city and county jails. A Council on Criminal Justice analysis found that in 2000, the rate of being on probation was 1.6 times higher and the rate of being parole was 3.6 times higher for Hispanics than non-Hispanic whites. But by 2016, the probation disparity had disappeared and the parole disparity had shrunk by 85%. Hispanics still faced a 60% higher risk of being incarcerated in a state prison. This is an enormous and worrying disparity, but the Council noted that it decreased by 60% since 2000. African-American and white disparities in parole, probation, jail, and incarceration have also declined in this century, but dwarf those that remain between Hispanics and whites.  

The dwindling of Hispanic-white disparities is even more remarkable in light of criminal behavior being so heavily concentrated in adolescence and young adulthood,. The median age for Hispanics is 29.8 years versus 43.7 for whites, meaning even in a system free of prejudice that punished solely on the basis of crimes committed, we would expect criminal justice disparities between the populations to be growing, not shrinking.

Parallel changes appear in who the criminal justice system employs. From 1997 to 2016, the proportion of police officers who were African-American was stable, whereas the proportion who were Hispanic increased 61%. This helps explain why a June 2021 Gallup poll found that the proportion of Hispanics expressing “a lot” or “a great deal” of trust in police was 49%, almost as high as whites (56%), and far greater than that of African-Americans (27%).  Hispanic views on policing and crime may also be similar to whites because the two groups rate of being violent crime victims is almost identical (21.3 per thousand persons for Hispanics, 21.0 for whites).   

The political implications of these changes are three-fold. First, in an era of widespread despair about criminal justice reform and racism in America more generally, the declining disparities between Hispanics and non-Hispanic whites merit reflection. A generation ago, the idea that such disparities would dramatically shrink or even disappear within the criminal justice system would have sounded naive. The fading of disparities should inspire reformers to even greater heights and also reduce cynicism about the alleged intractability of prejudice within American society. 

Second, politicians and activists should not assume that anti-police rhetoric will resonate with Hispanic voters, particularly in communities with heavily Hispanic police forces. Democrats’ weak performance with Latino voters (not just Cubans) in Miami-Dade County in 2020 stopped President Biden from winning the state and knocked two Democratic Members of Congress out of office. And while Trump’s Hispanic gains in other states do not appear to have been decisive, it’s easy to imagine these trends mattering in upcoming Senate races in Arizona, Nevada, and elsewhere.

Being tagged (fairly or unfairly) as favoring “Defunding the Police” in a county where nearly 6 in 10 officers are Hispanic surely did not help the Democrats’ cause, any more than pledging to eliminate policing jobs would have helped a candidate in Irish-American neighborhoods in Boston or Chicago or New York a century ago.  Working in law enforcement is a route that multiple ethnic groups throughout American history have used to clamber into the middle class, and Hispanics are following in that tradition. 

Third, all social movements contain the seeds of their own demise because if they succeed, their members are satisfied and begin drifting away. Reduced involvement in the correctional system and rising employment by and trust in police represent progress for Hispanics and should be celebrated; yet they also may lower the willingness of some Hispanics to get engaged with the criminal justice reform movement the country needs.  This is not inevitable if reformers are willing to modify their rallying cry.

[...]

Intimate partner violence data (quite old in many instances) — Asia, Africa

Intimate partner violence data (quite old in many instances)

1  Intimate partner violence in selected countries. Source: Prevalence Rates, Trends and Disparities in Intimate Partner Violence: Power of Data in the IPV Geospatial Dashboard. UN Population Fund, Feb 2021. https://asiapacific.unfpa.org/sites/default/files/pub-pdf/ipvdataanalysisreport_final.pdf

Afghanistan

In Afghanistan, where national 12-month IPV prevalence was 46.1 per cent according to the 2015  Afghanistan DHS, rates vary widely across the country. They range from 4.5 per cent in Helmand  Province to 90.3 per cent in Ghor (figure 2).

Tanzania

Similarly, the 2015–2016 Tanzania Demographic  Health Survey estimated that prevalence of intimate partner violence varied from 4.6 per cent in Pemba South to 56.8 per cent in Mara province (figure 3) while the national estimate was 29.6 per cent.

Nigeria

According to the 2018 Nigeria DHS, the national 12-month IPV prevalence rate measured 13.8 per cent and ranged from 2.6 per cent in Sokoto State to 35.6 per cent in Gombe State (figure 4). The 2017-2018 Jordan DHS estimated that nationally 13.8 per cent of ever-partnered women had experienced physical and/or sexual violence by a current or former partner in the previous 12 months, a figure that ranges from 3.0 per cent in Karak, to a high of 24.3 per cent in the Balqa Governorate (figure 5).

Ethiopia-Kenya border regions

Subnational data contributes to the identification of similar patterns in IPV prevalence across borders. For instance, the border of Ethiopia and Kenya shows similar levels of IPV between the Kenyan North-Eastern province (5.8 per cent) and the Ethiopian Somali province (5.8 per cent), as well as between the Kenyan Eastern province (25.1 per cent) and the Ethiopian Oromia province (25.3 per cent) (figure 6).

Mozambique-Zimbabwe border regions

The Manica province (22.5 per cent) and the Gaza province (21.9 per cent) in Mozambique also show similar rates of IPV prevalence with the bordering Manicaland province (23.6 per cent) and the Masvingo province (20.8 per cent) in Zimbabwe (figure 7).

Kenya — evolution

In Kenya, DHS data shows that in the North-Eastern province there was a substantial decrease in reported IPV prevalence, from 21.5 per cent in 2003 to 5.8 per cent in 2014. Conversely, reported IPV prevalence increased in Nairobi from 21.2 per cent in 2003 to 34.5 per cent in 2014 (figure 8).

Zimbabwe — evolution

In Zimbabwe, DHS data also indicate a substantial decrease in IPV prevalence in the Midlands, Mashonaland Central and Mashonaland Eastern provinces, from 38.9, 31.3 and 34.6 per cent respectively in 2006 to 17.9, 19.3 and 20.2 per cent in 2015 (figure 9)

India — evolution

In India, over the 10 years between 2006 and 2016, DHS data reveals reported increases in IPV in Tamil Nadu (21.0 to 35.2 per cent), Chhattisgarh (16.5 to 27.5 per cent) Andhra Pradesh (24.9 to 34.8 per cent), and Manipur (27.2 to 33.7 per cent). While decreases have been observed in Rajasthan (27.2 to 19 per cent), Uttaranchal (16.4 to 8.6 per cent), Kerala (10.9 to 9.5 per cent), Assam (26 to 17.3 per cent), Arunachal Pradesh (31.9 to 23.3 per cent) and Tripura (30.7 to 22.3 per cent). Finally, while IPV prevalence decreased only slightly in Bihar (44.1 to 37.5 per cent), it remains the State with the highest prevalence of IPV (figure 10).

In this document there are also chapters on education, wealth, rural-city environments.

2 Older data, source: Sexual violence in Papua New Guinea. Wikipedia, accessed Aug 29 2021. https://en.wikipedia.org/wiki/Sexual_violence_in_Papua_New_Guinea

2.1  Types

2.1.1  Violence against women

An estimated 67% of wives have been beaten by their husbands with close to 100% in the Highlands Region according to a 1992 survey by the PNG Law Reform Commission.[3][4] In urban areas, one in six women interviewed needed treatment for injuries caused by their husbands.[3] The most common forms of violence include kicking, punching, burning and cutting with knives, accounting for 80% to 90% of the injuries treated by health workers.[5]

An estimated 55% of women have experienced forced sex, in most cases by men known to them, according to a 1993 Survey by the PNG Medical Research Institute.[3][4][5] Abortion in Papua New Guinea is illegal unless it is necessary to save the woman's life, so those who experience pregnancy from rape have no legal recourse.

2.1.2  Violence against infants, children and adolescents

UNICEF describes the children in Papua New Guinea as some of the most vulnerable in the world.[6] According to UNICEF, nearly half of reported rape victims are under 15 years of age and 13% are under seven,[7] while a report by ChildFund Australia citing former Parliamentarian Dame Carol Kidu claimed 50% of those seeking medical help after rape are under 16, 25% are under 12 and 10% are under eight.[8]

Up to 50 percent of girls are at risk of becoming involved in sex work, or being internally trafficked.[6] Many are forced into marriage from 12 years of age under customary law.[6] One in three sex workers are under 20 years of age.[6]

2.1.3  Violence against men

A 2013 study found that 7.7% of men have sexually assaulted another male.[9]

2.1  Perpetrators

2.2.1  Statistics

A 2013 study by Rachel Jewkes and colleagues, on behalf of the United Nations Multi-country Cross-sectional Study on Men and Violence research team, found that 41% of men on Bougainville Island admit to coercing a non-partner into sex,[9] and 59% admit to having sex with their partner when she was unwilling.[10] According to this study, about 14.1% of men have committed multiple perpetrator rape.[9] In a survey in 1994 by the PNG Institute of Medical Research, approximately 60% of men interviewed reported to have participated in gang rape (known as lainap) at least once.[3]

2.2.2  Urban gangs

See also: Raskol gangs https://en.wikipedia.org/wiki/Raskol_gangs

In urban areas, particularly slum areas, Raskol gangs often require raping women for initiation reasons.[11] Peter Moses, one of the leaders of the "Dirty Dons 585" Raskol gang, stated that raping women was a “must” for the young members of the gang.[11] In rural areas, when a boy wants to become a man, he may go to an enemy village and kill a pig to be accepted as an adult, while in the cities "women have replaced pigs".[11] Moses, who claimed to have raped more than 30 women himself, said, “And it is better if a boy kills her afterwards, there will be less problems with the police”.[11]

3  Sobering data in a single cartogram (map with lots of associated data). Source: 2020 map of violence against women prevalence in Asia-Pacific region. UN Population Fund, July 2020. https://asiapacific.unfpa.org/en/resources/violence-against-women-regional-snapshot-2020-knowvawdata

Humans are social animals, but not everyone will be mindful of others to the same extent: Social mindfulness and prosociality vary across the globe (study of 31 nations and regions)

Social mindfulness and prosociality vary across the globe. Niels J. Van Doesum. Proceedings of the National Academy of Sciences, August 31, 2021 118 (35) e2023846118; https://doi.org/10.1073/pnas.2023846118

Significance: Cooperation is key to well-functioning groups and societies. Rather than addressing high-cost cooperation involving giving money or time and effort, we examine social mindfulness—a form of interpersonal benevolence that requires basic perspective-taking and is aimed at leaving choice for others. Do societies differ in social mindfulness, and if so, does it matter? Here, we find not only considerable variation across 31 nations and regions but also an association between social mindfulness and countries’ performance on environmental protection. We conclude that something as small and concrete as interpersonal benevolence can be entwined with current and future issues of global importance.

Abstract: Humans are social animals, but not everyone will be mindful of others to the same extent. Individual differences have been found, but would social mindfulness also be shaped by one’s location in the world? Expecting cross-national differences to exist, we examined if and how social mindfulness differs across countries. At little to no material cost, social mindfulness typically entails small acts of attention or kindness. Even though fairly common, such low-cost cooperation has received little empirical attention. Measuring social mindfulness across 31 samples from industrialized countries and regions (n = 8,354), we found considerable variation. Among selected country-level variables, greater social mindfulness was most strongly associated with countries’ better general performance on environmental protection. Together, our findings contribute to the literature on prosociality by targeting the kind of everyday cooperation that is more focused on communicating benevolence than on providing material benefits.

Keywords: social mindfulnesscross-national differenceslow-cost cooperation

Discussion

Large-scale, industrialized societies differ in low-cost cooperation as operationalized using SoMi; in this broad overview, we found strong support for substantial cross-national variation (Fig. 1). This confirms that research on cooperation should look at nation-level differences (cf. ref. 28). Across three broad themes, SoMi was associated with individual trust and SVO and some societal and economic indices (religiosity, power distance, GDP, and Gini) but most strongly with the level of EPI within the targeted countries. We also found limited associations with demographic variables (parental education and SES). Ranking and pattern of associations for SoMi and SVO overlapped meaningfully but not substantially, confirming that low-cost cooperation should be investigated independently from costly cooperation.

Our primary aim was to provide an overview of cross-national differences in SoMi. The proportion of socially mindful decisions differed considerably across the samples in our study. Scores ranged from 46.2 (Indonesia) to 72.0% (Japan), with a gradual incline between the lowest and highest values (see Fig. 1). This pattern indicates that low-cost cooperation varies across nation-based populations and should be further investigated. Other than costly cooperation measured using tasks with monetary consequences, there is little research on nonmonetary, low-cost cooperation, even though “social life also involves low-cost cooperation, such as information sharing, showing respect, and conveying appreciation such as gratitude and compliments” [(36), p. 503].

Exploring potential mechanisms in a second step, we organized selected variables in three broader themes. Within the first theme, trusting others was associated with SoMi at individual level but not at country level. A common factor in research on costly cooperation (26, 30, 37), this finding could suggest that functional trust in low-cost cooperation is different from how trust operates in costly cooperation; however, scale reliability was low, and conclusions should be treated with caution. Looking at social preferences, we did find the expected positive association with SVO, which was moderate at individual level and larger at country level (4). Fig. 1 illustrates this correlation but at the same time shows clear differences of where countries are on the list. This distinction is corroborated by a fully different pattern of associations in step two of the analyses across all three themes. Only level of education seems to provide common ground, but even there it concerns parental (SoMi) versus individual (SVO) education. Together these findings provide evidence for the unique place of low-cost cooperation in general and SoMi in particular within the broader concept of human cooperation.

The second theme, investigations of selected societal variables and economic indices at country level, showed higher levels of SoMi for countries with lower levels of religiosity. This brings to mind that the common positive association between religiosity and subjective well-being strongly depends on societal factors; difficult life circumstances predict higher religiosity and thus greater well-being (38). SoMi seems associated with easier life circumstances, as indicated by associations with GDP, GNI, and Gini. We did not measure individual level religiosity, however, which makes it unclear if and how religiosity and SoMi are connected at the personal level. The simple relation between religiosity and cooperation in the literature (e.g., ref. 39) would suggest a positive association (but see refs. 26 and 40), and the community aspect of many religions could well promote SoMi, at least within one’s own community (2, 5). Additionally, the democratically installed and maintained rule of law showed a positive association with SoMi. The negative association with power distance (Hofstede dimensions) points in the same direction: SoMi—low-cost cooperation—is not driven by obeying those in power but by truly interpersonal relations in which others are seen and acknowledged as equals living under the same norms (3).

Following the third theme, SoMi was not correlated at individual level with most of the demographic variables we investigated. Although several correlations were statistically significant, effect sizes were generally too small to be meaningful. At country level, we found that SoMi was positively associated with parental education but negatively with SES. Seemingly contradictory, both parental education and SES are used as operationalizations of social class. One explanation for the divergent pattern is that parental education reflects what often is described as cultural capital, or class background (41), whereas the social ladder as a measure of subjective social class is based on one’s actual economic assessment, or class foreground (42, 43). Foreground and background complement each other but do not automatically overlap. That SoMi is positively related with background cultural capital but negatively with foreground economic hierarchy once more underlines that SoMi skips the economic costs. It also shows that social class is and remains a complex and multifaceted phenomenon to define (6).

Among all potential mechanisms we investigated, one solid effect needs to be highlighted. The country-level association between SoMi and EPI that washed out all other relations in our final model suggests that prosocial tendencies may not only be revealed in people’s orientation toward individual strangers but also toward a collective of strangers with a broader concern for environmental sustainability. This broader concern specifically combines protection of environmental health with the protection of ecosystems (44). The positive association connects with growing research on the social aspects of biodiversity conservation and sustainability initiatives that suggests that greater social capital is accompanied by greater and more successful environmental protection (45, 46), possibly a form of collective action (47). In terms of the SoMi paradigm, SoMi may not only reflect how people leave others choice at a micro level but also how they may want to leave the broader community of others a reasonably healthy earth to live on at a macro level. SoMi, then, is shaped by a socially interconnected environment in which the awareness of a “we,” “us,” and “our future” may all be equally accessible units of thought and action. Among other things, this may promote a social and political climate that helps recognize, address, and reduce climate change.

In the end, what best explains the general picture? Considering all findings, we suggest that SoMi may be conceptualized as a specific and effective expression of social capital (47⇓⇓–50), a comprehensive perspective on society with important implications for its development and functioning (30). Following one of the definitions, the economic function of social capital is to diminish the costs of formal coordination tasks by using informal social communication channels (51). From a relational perspective, such capital materializes through social interactions that include low-cost cooperation. Requiring no monetary or otherwise effortful investments to acknowledge, confirm, and promote high-trust social relationships, SoMi would be specifically set up to do so; the socially mindful person signals benevolence and trustworthiness (2, 3, 21). A promising connection with social capital is also suggested in the ranking of our locations: Japan, highest on the SoMi list, is traditionally known for stressing the value of social capital (52), and ranks 12th (of 180) on the Global Sustainable Competiveness Index social capital world index (53), while Indonesia, lowest on the SoMi list, ranks 70. A simple bivariate correlation without corrections learns that SoMi and social capital scores are associated at r (30) = 0.56, P = 0.002. Although quantifying social capital is difficult, this is corroborated by the relations we found between SoMi and the ensemble of variables lead by EPI and followed by economic indices (GDP, GNI, and Gini), rule of law, power distance, individual and generalized trust, and civic cooperation (tendency only), which all in their own way have been connected to presence and development of social capital (45⇓–47, 51). Future research could develop this.

Limitations and Future Research.

It should be noted that our findings specifically pertain to low-cost cooperation as measured using SoMi and that different results may be obtained when material costs of cooperation become high(er). Higher costs could make self-related thoughts more salient and thus may move people away from a “we mode” of thinking that is more natural for low-cost cooperation. Moreover, our explanation of SoMi as low-cost prosociality is mainly theoretical. To complete our tests, future research could compare SoMi with specific other forms of low-cost (e.g., helping that does not require time or effort) and costly cooperation (e.g., dictator or ultimatum games) in terms of important background psychological variables like personal values, personality (4, 54, 55), trust, intra- and intergroup dynamics, generalized reciprocity, and identification with the collective (56). One suggestion would be that low-cost cooperation is more common and even more intuitive than high-cost cooperation (57, 58). Numerous daily situations lend themselves to simple decisions that reflect regard for others—see our wine choice example—and have more important outcomes at the relational level than with regards to resource allocation. This makes it likely that for many individuals, kind behaviors are a matter of habit without much deliberation, but only when it does not cost them.

Importantly, the current data provide preliminary evidence; confirmatory research is certainly needed. Our findings are based on a cross-national investigation among mostly young, college-aged individuals, mainly in cities with reasonable access to universities or other institutions of higher education. As much as this constrains generalizability, however, the strength of this approach is that it provided much-needed experimental control and comparability between samples in this initial research. For a next step, more general samples could be targeted. Moreover, the mechanisms we examined were derived from three common theoretical frameworks but, given the novelty of the construct to cross-national comparisons, remain largely exploratory. For example, there may be factors we have not included that could shed more light on why SoMi varies across nations and regions. Hence, we strongly recommend follow-up research to include different samples that are representative of other parts of the population and use complementary experimental designs.

From 2003...The Second Law of Thermodynamics Is the First Law of Psychology: Evolutionary Developmental Psychology and the Theory Of Tandem, Coordinated Inheritances

From 2003... Tooby, J., Cosmides, L., & Barrett, H. C. (2003). The Second Law of Thermodynamics Is the First Law of Psychology: Evolutionary Developmental Psychology and the Theory Of Tandem, Coordinated Inheritances: Comment on Lickliter and Honeycutt (2003). Psychological Bulletin, 129(6), 858–865. https://doi.org/10.1037/0033-2909.129.6.858

Abstract: Organisms inherit a set of environmental regularities as well as genes, and these two inheritances repeatedly encounter each other across generations. This repetition drives natural selection to coordinate the interplay of stably replicated genes with stably persisting environmental regularities, so that this web of interactions produces the reliable development of a functionally organized design. Selection is the only known counterweight to the tendency of physical systems to lose rather than grow functional organization. This means that the individually unique and unpredictable factors in the web of developmental interactions are a disordering threat to normal development. Selection built anti-entropic mechanisms into organisms to orchestrate transactions with environments so that they have some chance of being organization-building and reproduction-enhancing rather than disordering.

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As evolutionary psychologists, we believe in design reincarnation based on two inheritances, not genetic preformationism based on one.

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Lessons for Psychology From Thermodynamics and Darwinism

The most basic lesson is that natural selection is the only known natural process that pushes populations of organisms thermodynamically uphill into higher degrees of functional order, or even offsets the inevitable increase in disorder that would otherwise take place. Therefore, all functional organization in undomesticated organisms that is greater than could be expected by chance (which is nearly all functional organization) is ultimately the result of the operation of natural selection and hence must be explained in terms of it (if it is to be explained at all). This is why understanding natural selection is enormously beneficial to any theoretically principled psychology. In effect, natural selection defines the design criteria to which organisms were built to conform. This is why knowledge of ancestral natural selection combined with knowledge of ancestral environments provides a principled theoretical framework for deriving predictions about the reliably developing design of the human mind. Natural selection is (a) the set of enduring, nonrandom, cause-and-effect relationships in the world that (b) interact with the reliably developing features of organisms (c) in such a way that they consistently cause some design variants to reproduce their designs more frequently than others because of their design differences. Hence, those traits that do not reliably develop across generations cannot be systematically interacted with by selection and thus will not be organized by the long-term operation of selection. Reciprocally, if a property of the world does not stably endure across generations, then it will not last long enough to cause some design features to supplant others in large populations, and its effects will not show up in the species-typical designs of organisms. Selection brings about a functional coordination between the stable, long-term properties of environments and the stable, cross-generationally recurrent, reliably developing (and hence predictable or prespecifiable) properties of organisms. In contrast, there is no process that guarantees that unique, novel interactions between environments and organisms will be functional. Hence, natural selection predicts and explains the extraordinarily nonrandom, functionally organized relationships that interpenetrate the species-wide designs of all organisms, including humans. Whenever one sees functional order, one is seeing the downstream contrivances of natural selection.

The outcomes of over 5 million chess games were analyzed; controlling for differences in chess skills, there was an enhanced performance among players who were competing outside of their home countries; advantage is approx 2%

The performance advantage of traveling. Uri Zak. Journal of Economic Psychology, August 28 2021, 102431. https://doi.org/10.1016/j.joep.2021.102431

Abstract: Many individuals travel between countries as part of their professional routines. How do they perform during those short trips abroad? To begin to answer this question, I analyzed the outcomes of over 5 million chess games played around the world. Importantly, tournament chess provides a clean setting in which location-dependent factors are mostly irrelevant; the audiences are quiet and the referees make hardly any judgments. Controlling for differences in chess skills, I found enhanced performance among players who were competing outside of their home countries. This finding was robust to additional controls such as age, sex, and skill momentum or game practice, and to the inclusion of individual or country fixed effects. This advantage, an approximately 2% increase in game outcome, suggests that traveling has a positive effect on performance.

Keywords: Home advantageChessCognitive performanceTravelSports

Similarities and differences in concepts of mental life among adults and children in five cultures (US, Ghana, Thailand, China, & Vanuatu)

Similarities and differences in concepts of mental life among adults and children in five cultures. Kara Weisman, Cristine H. Legare, Rachel E. Smith, Vivian A. Dzokoto, Felicity Aulino, Emily Ng, John C. Dulin, Nicole Ross-Zehnder, Joshua D. Brahinsky & Tanya Marie Luhrmann. Nature Human Behaviour, Aug 26 2021. https://www.nature.com/articles/s41562-021-01184-8

Abstract: How do concepts of mental life vary across cultures? By asking simple questions about humans, animals and other entities – for example, ‘Do beetles get hungry? Remember things? Feel love?’ – we reconstructed concepts of mental life from the bottom up among adults (N = 711) and children (ages 6–12 years, N = 693) in the USA, Ghana, Thailand, China and Vanuatu. This revealed a cross-cultural and developmental continuity: in all sites, among both adults and children, cognitive abilities travelled separately from bodily sensations, suggesting that a mind–body distinction is common across diverse cultures and present by middle childhood. Yet there were substantial cultural and developmental differences in the status of social–emotional abilities – as part of the body, part of the mind or a third category unto themselves. Such differences may have far-reaching social consequences, whereas the similarities identify aspects of human understanding that may be universal.

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We asked simple questions (Do beetles remember things? Do ghosts get hungry? Do chickens feel love?), and used people's answers to reconstruct concepts of mental life from the bottom up among adults and 6-12yo children in the US, Ghana, Thailand, China, & Vanuatu

Multivariate analysis of 1.5 million people identifies 579 genome-wide significant loci associated with a liability toward externalizing outcomes (problems of self-regulation and addiction)

Multivariate analysis of 1.5 million people identifies genetic associations with traits related to self-regulation and addiction. Richard Karlsson Linnér et al. Nature Neuroscience, Aug 26 2021. https://www.nature.com/articles/s41593-021-00908-3

Abstract: Behaviors and disorders related to self-regulation, such as substance use, antisocial behavior and attention-deficit/hyperactivity disorder, are collectively referred to as externalizing and have shared genetic liability. We applied a multivariate approach that leverages genetic correlations among externalizing traits for genome-wide association analyses. By pooling data from ~1.5 million people, our approach is statistically more powerful than single-trait analyses and identifies more than 500 genetic loci. The loci were enriched for genes expressed in the brain and related to nervous system development. A polygenic score constructed from our results predicts a range of behavioral and medical outcomes that were not part of genome-wide analyses, including traits that until now lacked well-performing polygenic scores, such as opioid use disorder, suicide, HIV infections, criminal convictions and unemployment. Our findings are consistent with the idea that persistent difficulties in self-regulation can be conceptualized as a neurodevelopmental trait with complex and far-reaching social and health correlates.

This chapter argues that the conventional theories and processes at the core of the discipline of political communication are rooted in assumptions that no longer hold and contexts that no longer exist

Young, Dannagal G., & Joanne Miller 2021. “Young and Miller, Political Communication in Oxford Handbook of Poli Psych 3rd Ed.” OSF Preprints. August 27. doi:10.31219/osf.io/mwdtu

Abstract: This chapter argues that the conventional theories and processes at the core of the discipline of political communication are rooted in assumptions that no longer hold and contexts that no longer exist. Today’s media users experience decentralized, interpersonal, horizontal, networked politically relevant communication every day. And they experience this socially-contextualized messaging within a system predicated on the economics and logics of micro-segmentation. We assert that these are qualitative shifts that necessitate a fundamental reconsideration and reimagining of the field of political communication. Specifically, we focus on how the shift away from traditional mass media models to networked, decentralized media systems through digital technologies has crucial implications for: a) the scope of what constitutes political communication and b) the integration of political psychology into the study of political communication.

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Echo Chambers. Another implication of the increasingly interpersonal nature of media experiences and the micro-segmentation of audiences is the potential formation of echo chambers and filter bubbles. As media choice increases, individuals can increasingly “opt in” or “out” of media experiences, facilitating selective exposure to and avoidance of ideologicallyconsonant – or even politically-relevant (Prior, 2007) – media content. In their paradigmchallenging essay, Bennett and Iyengar (2008) suggested that selectivity behaviors would be so great in this new media landscape, that media persuasion effects would all but disappear, even as other effects like agenda setting or priming might continue. “As media audiences devolve into smaller, like-minded subsets of the electorate,” they wrote, “it becomes less likely that media messages will do anything other than reinforce prior predispositions. Most media users will rarely find themselves in the path of attitude-discrepant information.” (p. 724).

Such “echo chambers” or “filter bubbles” became a growing concern among political scientists and political communication scholars from 2000 - 2010s (Sunstein, 2001), as empirical examinations pointed to a public engaging in selective exposure and avoidance of politicallydissonant mediated information in ways that could fuel political polarization (Stroud, 2011; see below). Yet, while echo chambers and filter bubbles are certainly made possible through media fragmentation, research has failed to produce substantial evidence to support the notion that most people restrict themselves to only like-minded media content (see Guess et al, 2018; Guess, 2021). Although selective exposure to like-minded content does occur, and moral-emotional content from elites spreads efficiently within their ideological social networks (especially on the 27 right) (Brady et al., 2019), evidence of selective-avoidance of belief-disconfirming information is scarce (Garrett, 2009). Barbera et al, (2015) conclude that “homophilic tendencies in online interaction do not imply that information about current events is necessarily constrained by the walls of an echo chamber” (p. 1539). Users tend to have diverse media diets and vary in the extent to which they pay attention to political or current events information (Guess, 2018), and those users who do pay attention to like-minded political content, pay more, not less attention to belief-dissonant programming (Garrett, Carnahan, & Lynch, 2011, Nelson & Webster, 2017). Even on social media, where algorithms and users themselves increase the ideological homogeneity of their newsfeeds (Bakshy, Messing, and Adamic 2015), users are still exposed to some belief-disconfirming information. In fact, in the most fragmented context of all, the internet, selective exposure and avoidance is complicated by social networks, where social media posts of friends and family can serve as heuristics that guide ideologically diverse information consumption (Masip, SuauMartinez, & Ruiz-Caballero, 2017; Messing and Westwood, 2014; Flaxman, Goel, & Rao, 2016; Zuiderveen et al., 2016), even trumping partisan selective exposure (Anspach, 2017). These results are supported by Dylko et al (2018) who find that although customized media experiences increase selective exposure dynamics in ways that increase political polarization, this effect is limited to customization processes that are automatically embedded within a technology. When users have the ability to customize media experiences, these relationships shrink, again highlighting how user agency often diversifies – rather than homogenizes – media diets. Such findings certainly call into question Bennett and Iyengar’s (2008) pronouncement of the “demise of the inadvertent audience” (p. 717). Whereas media fragmentation facilitates selective exposure and avoidance, the interpersonal networked nature of the social media experience does not. Yet attending to and being receptive to belief-disconfirming content are two different things that may be motivated by different goals. Knobloch-Westerwick and Klienman (2012), for example, find that people engage in less selective avoidance of belief-disconfirming information when they expect their side is going to lose, pointing to anticipated “informational utility” as individuals anticipate that exposure to belief-disconfirming content “can aid individuals in making future decisions” (p. 171). Valentino et al.’s (2009) work is consistent with this explanatory mechanism, with individuals seeking out belief-disconfirming content as a way of monitoring their information environments. In this work, anxiety was found to fuel information seeking behaviors, thereby increasing exposure to belief-disconfirming content, illustrating that these consumption behaviors are shaped by emotional needs of the audience. Finally, calls to relax the fears of echo chambers and filter bubbles are focused on the modal cases – the most likely outcomes for most people. This raises questions about whether we should be more concerned about the outcomes of users at the margins - culturally and politically. Boutyline and Willer (2017) for example, found that social networks (on Twitter) were most homogenous among those users with the most extreme political views. Evidence about the moderating role of political engagement is mixed; Guess (20121 finds a positive relationship between political engagement and media diet homogeneity, whereas Dubois and Blank (2018) find the reverse (see also Eady et al. 2019). Emotions such as anger may fuel the kind of dynamics that lead to concerning echo-chambers, while fear and anxiety may mitigate them (Wollebaek et al., 2019). Recent work by Stier et al. (2020) indicates that populist attitudes interact with contextual factors to fuel selective exposure patterns, with populist attitudes 29 contributing to lower (but not zero) exposure to traditional news and greater exposure to hyperpartisan outlets.

Investors who are male, or above the age of 45, or married, or have more dependents, or who self-identify as having excellent investment experience or knowledge tend to freak out with greater frequency

Elkind, Daniel and Kaminski, Kathryn and Lo, Andrew W. and Siah, Kien Wei and Wong, Chi Heem, When Do Investors Freak Out?: Machine Learning Predictions of Panic Selling (August 4, 2021). SSRN: http://dx.doi.org/10.2139/ssrn.3898940

Abstract: Despite standard investment advice to the contrary, individuals often engage in panic selling, liquidating significant portions of their risky assets in response to large losses. Using a novel dataset of 653,455 individual brokerage accounts belonging to 298,556 households, we document the frequency, timing, and duration of panic sales, which we define as a decline of 90% of a household account’s equity assets over the course of one month, of which 50% or more is due to trades. We find that a disproportionate number of households make panic sales when there are sharp market downturns, a phenomenon we call ‘freaking out’. We show that panic selling and freak outs are predictable and fundamentally different from other well-known behavioral patterns such as over trading or the disposition effect. Investors who are male, or above the age of 45, or married, or have more dependents, or who self-identify as having excellent investment experience or knowledge tend to freak out with greater frequency. We use a five-layer neural network model to predict freak out events one month in advance, given recent market conditions and an investor’s demographic attributes and financial history, which exhibited true negative and positive accuracy rates of 81.5% and 69.5%, respectively, in an out-of-sample test set. We measure the opportunity of cost of panic sales and find that, while freaking out does protect investors during a crisis, such investors often wait too long to reinvest, causing them to miss out on significant profits when markets rebound.

Keywords: Panic Selling; Stop-Loss; Tactical Asset Allocation; Freaking Out; Deep Learning; Behavioral Finance

JEL Classification: G11, G01, G02, D14, D91

Given the overwhelming whiteness of BDSM in both research and practice, we need to build inclusive BDSM communities that continue to naturalize this whiteness

Overwhelming whiteness of BDSM: A critical discourse analysis of racialization in BDSM. Katherine Martinez. Sexualities, July 17, 2020. https://doi.org/10.1177/1363460720932389

Abstract: Ahmed’s (2007) theory of the phenomenology of whiteness serves as a theoretical tool for assessing how whiteness presents itself within bondage, discipline, dominance/submission, and sadomasochism (BDSM) play. Given the “overwhelming whiteness” of BDSM in both research and practice, this study serves as a theory-building exercise for analyzing the relationship between what researchers have described as inclusive BDSM communities that continue to naturalize the whiteness of BDSM spaces. Through critical discourse analysis of interviews and blog submissions from BDSM participants, this study reflects on the whiteness of BDSM. Analyses suggest that the differences between white and racialized BDSM participants in their explanations for the whiteness of BDSM continue to support and privilege the white experience in white BDSM spaces.

Keywords: Critical discourse analysis, racialization, sadomasochism, whiteness

Consecration in American Sociology, 1980–2020: The number of awards & honorable mentions has grown dramatically despite the number of American Sociology Asssociation sections being constant & membership having declined

Visualizing the Expanding Space of Consecration in American Sociology, 1980–2020. Nicholas Hoover Wilson, Damon Mayrl. Socius: Sociological Research for a Dynamic World, August 26, 2021. https://doi.org/10.1177/23780231211038366

Abstract: This visualization explores changes in the scope and dynamics of consecration within American sociology by examining awards granted to members of the American Sociological Association’s (ASA) constituent sections. Consecration is important because it signals quality to nonspecialists, boosts intellectual careers, and can be a crucial vector introducing various forms of inequality. We show that with ASA sections, the number of awards, multiple award winners, and honorable mentions has grown dramatically, especially since 2010, and that this has occurred even as the number of ASA sections has remained constant and overall ASA membership has declined.

Keywords: knowledge, science, consecration, awards, academic disciplines

Capuchin monkeys: Cognitive performance was impaired by negative experiences; contrary to predictions, positive experiences did not have a facilitative effect on cognitive performance

Webster, M. F., & Brosnan, S. F. (2021). The effects of positive and negative experiences on subsequent behavior and cognitive performance in capuchin monkeys (Sapajus [Cebus] apella). Journal of Comparative Psychology, Aug 2021. https://doi.org/10.1037/com0000277

Abstract: Our understanding of animals’ affective processing is notably limited compared to the wealth of research on humans, largely due to difficulties in measurement. Moreover, despite a recent increase in the understanding of the interaction between affect and cognition in animals, most research has focused on negative affect, with the result that we continue to know little about the effects of positive affect. In this study, we tested 15 adult capuchin monkeys (Sapajus [Cebus] apella) using a novel methodology that took advantage of capuchins’ species-typical behavior to engineer both a positive and negative experience, using the same apparatus to minimize extraneous impacts. Following a positive or negative experience (that presumably induced positive and negative affect, respectively), or a control with no manipulation, we assessed subjects’ performance on a cognitive task, a computerized delayed match-to-sample. As predicted, behavior following the negative condition suggested a negative affective state, with increased rates of scratching (commonly used as an indicator of stress in nonhuman primates) compared to both the positive and control conditions. Cognitive performance was also impaired in the negative condition compared to the other two. Contrary to predictions, however, the positive condition did not have a facilitative effect on cognitive performance, but behavioral results indicate that we may not have induced a truly positive affective state. Although we add to evidence that a negative experience can influence subsequent behavior and cognitive performance in nonhuman primates, our work highlights our lack of knowledge about the impact of positive affect, if any, on behavior and cognition.

Jealousy was 29% heritable, and non-shared environmental influences explained the remaining variance (71%); no transmission of relationship models from parents to children

Why are some people more jealous than others? Genetic and environmental factors. Tom R. Kupfer et al. Evolution and Human Behavior, August 27 2021. https://doi.org/10.1016/j.evolhumbehav.2021.08.002

Abstract: Research on romantic jealousy has traditionally focused on sex differences. We investigated why individuals vary in romantic jealousy, even within the sexes, using a genetically informed design of ~7700 Finnish twins and their siblings. First, we estimated genetic, shared environmental and nonshared environmental influences on jealousy, Second, we examined relations between jealousy and several variables that have been hypothesized to relate to jealousy because they increase the risk (e.g., mate-value discrepancy) or costs (e.g., restricted sociosexuality) of infidelity. Jealousy was 29% heritable, and non-shared environmental influences explained the remaining variance. The magnitude and sources of genetic influences did not differ between the sexes. Jealousy was associated with: having a lower mate value relative to one's partner; having less trust in one's current partner; having been cheated by a previous or current partner; and having more restricted sociosexual attitude and desire. Within monozygotic twin pairs, the twin with more restricted sociosexual desire and less trust in their partner than his or her co-twin experienced significantly more jealousy, showing that these associations were not merely due to the same genes or family environment giving rise to both sociosexual desire or trust and jealousy. The association between sociosexual attitude and jealousy was predominantly explained by genetic factors (74%), whereas all other associations with jealousy were mostly influenced by nonshared environmental (non-familial) factors (estimates >71%). Overall, our findings provide some of the most robust support to date on the importance of variables predicted by mate-guarding accounts to explain why people vary in jealousy.

Keywords: JealousyTwinsMate value discrepancyTrustInfidelitySociosexualityIndividual differencesGenetics

4. Discussion

The current research aimed to shed light on why people differ in romantic jealousy. Our findings suggest that people differ in jealousy partly because of genetic influences, but mostly because of nonshared environmental influences. We did not detect an influence of the shared environment on jealousy. We also examined associations between jealousy and specific variables that have been hypothesized by mate-guarding accounts to influence jealousy proneness. Our findings provide some of the most robust evidence to date that mate value discrepancy, trustworthiness of a mate, and sociosexuality are associated with romantic jealousy.

Overall, 29% of variation in jealousy was attributable to genetic factors, with the remainder attributable to the nonshared environment. This genetic contribution to variation is on the low side compared to other psychological traits, including measurements of personality and emotions, for which the heritability is typically closer to 50% (Polderman, Benyamin, de Leeuw, et al., 2015). However, our finding is in line with those of Walum, Larsson, Westberg, Lichtenstein, and Magnusson (2013), who reported that sexual and emotional jealousy were 32% and 26% heritable, respectively. Also in line with Wallum et al., we found no evidence for sex differences in the magnitude of genetic and environmental influences on jealousy, or for different genetic or non-shared environmental influences operating in men or women. In other words, even though women reported higher jealousy than men, individual variation in jealousy within the sexes was influenced similarly by genetic and environmental factors.

The finding that familial environmental influences did not influence jealousy has theoretical implications. According to influential accounts of attachment theory, mental models of relationship expectations are transmitted from parents to children, through learning during infancy (Fonagy & Target, 2005; Van IJzendoorn, 1995; Verhage et al., 2016; c.f., Barbaro et al., 2017), and these mental models later determine emotion reactions, including jealousy, towards perceived relationship threats in adulthood (Mikulincer & Shaver, 2005; Sharpsteen & Kirkpatrick, 1997). Our finding that variation in jealousy is not influenced by familial environmental factors, which includes parenting, is inconsistent with these accounts. An implication is that research that seeks to understand variation in – and the development of – jealousy should attend more to genetic and nonshared environmental influences than to shared environmental factors such as parenting behavior. However, one caveat is that a limitation of twin studies is that they do not control for genetic and environmental interplay (for example, parental genes shaping the twin's family environment) which can confound the estimate of the influence of the family environment (Keller, Medland, & Duncan, 2010). Therefore, it is safest to say that we found no influence of the family environment ‘independent of genetic factors’ (Turkheimer, D'Onofrio, Maes, & Eaves, 2005).

In contrast to attachment theory's parental transmission account, mate-guarding perspectives hypothesize that jealousy should be primarily influenced by factors that increase the risk of infidelity by one's mate (Buss, 2013). These will often be socio-ecological variables (e.g., the attractiveness of one's mate, or the number of rivals in one's environment) which presumably derive more from the nonshared environment than the shared environment. Our finding of a substantial nonshared environmental influence on variation in jealousy is therefore consistent with mate-guarding accounts (though not uniquely consistent with those accounts). Note, however, that the estimate of the nonshared environment also includes measurement error.

The second aim of our study was to examine three of the variables predicted by mate-guarding accounts to influence jealousy: mate value discrepancy, cues to a mate's likelihood of infidelity (namely trust and actual experiences of infidelity), and sociosexuality. The strongest predictors of jealousy were more restricted sociosexual attitude and desire. Further, these relations were stronger for people in a relationship and for women. More sociosexually-restricted individuals may be more invested in fewer relationships and more motivated to protect them and, hence, experience more jealousy in response to cues to infidelity threats (Brase et al., 2014; Buss, 2013; Russell & Harton, 2005). Previous studies have most often not detected associations between jealousy and sociosexual orientation (Harris, 2003; Peters et al., 2014; Russell & Harton, 2005), but our findings were based on a much larger sample of individuals (N > 7000) than previous studies. The current finding was further strengthened by the discordant-twin design analysis within monozygotic twin pairs, which also detected a negative association between sociosexual desire and jealousy. This approach suggests that the association does not arise merely because sociosexual desire and jealousy emerge from the same genetic or family environmental sources. Results from the bivariate twin analyses were in accordance because they showed that nonshared environmental factors instead of familial factors explained the majority of the association (71%). Although it is therefore possible that restricted sociosexual desire causes higher jealousy, co-twin-control analyses cannot guarantee causal relationships or rule out reverse causation (McGue et al., 2010). Reverse causation (or bi-directional causation) is plausible, if, for example, individuals with higher jealousy pursue more exclusive relationships to reduce the possibility of infidelity by their mate.

Consistent with previous findings, people who reported being cheated on in the past, and those cheated on in their current relationship, also reported greater jealousy (Bendixen et al., 2015; Burchell & Ward, 2011; Edlund et al., 2006; Murphy et al., 2006; Sagarin et al., 2003). Additionally, having lower trust in one's partner was associated with higher jealousy (both on individual level and when we compared monozygotic co-twins discordant on trust in their partner). Therefore, findings suggest that variables assessing cues to a mate's likelihood of infidelity (trust and actual experiences of infidelity) relate to jealousy.

Also consistent with previous studies (Buss & Shackelford, 1997; Sidelinger & Booth-Butterfield, 2007), individuals who reported having a lower mate value than their partner reported higher jealousy. When examining associations within monozygotic twins only, those associations were non-significant (unlike associations between jealousy and sociosexual desire and mate trustworthiness), so the possibility that the association is due to similar genes influencing both mate value discrepancy and jealousy cannot be ruled out. However, the regression betas in the discordant twin design did not decrease in size, suggesting that the sample size of monozygotic twins may have been underpowered to detect an association. Moreover, the bivariate analyses did not detect familial influences on the association between jealousy and mate value discrepancy, indicating that the association between mate value discrepancy and jealousy is unlikely to be explained by similar genes or shared familial influences.

The study has some limitations. First, all measurements were based on self-reports. While the use of self-report questionnaires is common in psychology research (including most of the jealousy literature), they can be prone to measurement bias due to factors such as social desirability, which could, for example, have contributed to the low prevalence of cheating reported in our sample. Nonetheless, our self-report jealousy scale, which used 11 items describing jealousy-eliciting situations of varying severity, was likely to be a more sensitive measure of jealousy than measures commonly used. Many previous studies (e.g., Walum et al., 2013) have assessed jealousy with only two items asking participants how upset they would be in response to their partner's sexual infidelity and their partner's emotional infidelity. Another limitation was that the sample of discordant twin pairs contributing to the discordant-twin design analyses was much smaller than the sample in the overall regression analyses. Therefore, non-significant effects of sociosexual attitude, being cheated on in the past, and mate value discrepancy on jealousy within monozygotic twins could be due to lower power in these analyses. There are other potentially influential environmental variables that we were not able to assess in the current research. For example, perceived number and quality of rivals has been hypothesized to increase jealousy by increasing risks of cuckoldry or mate poaching (Buss, 2013; Pollet & Saxton, 2020), and perspectives other than the mate-guarding account propose that variables such as self-esteem are associated with jealousy (DeSteno, Valdesolo, & Bartlett, 2006). Future research on these factors using genetically informed studies would be valuable. Additionally, future research would benefit from using children-of-twins or nuclear twin designs that allow for the estimation of interplay between sources of variance that are impossible to disentangle using classical twin designs and might bias estimation of shared environmental influences (Keller et al., 2010).

In summary, this study confirms that people differ in jealousy partly because of genetic influences, but mostly because of nonshared environmental influences. Our findings provide some of the most robust evidence in support of several factors that have been hypothesized by mate-guarding accounts to influence jealousy proneness, and show that these factors similarly influence both men and women. Discerning the causes of variation in jealousy is an important step towards tackling the socially harmful consequences of jealousy, such as domestic violence and homicide.