The pandemic exposes human nature: 10 evolutionary insights.

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.

There are no beautiful surfaces without a terrible depth.

Fitouchi et al. persuasively argue against popular disgust-based accounts of puritanical morality. However, they do not consider alternative account of moral condemnation that is also based on the psychology of disgust. We argue that these other disgust-based accounts are more promising than those dismissed in the target article.

Evaluating Benefits, Costs, and Social Value as Predictors of Gratitude.

Although much is known about cooperation, the internal decision rules that regulate motivations to initiate and maintain cooperative relationships have not been thoroughly explored. Here, we focus on how acts of benefit delivery and perceptions of social value inform gratitude, an emotion that promotes cooperation. We evaluated alternate information-processing models to determine which inputs and internal representations best account for the intensity with which people report experiencing gratitude. Across two experiments (Ns = 257 and 208), we tested 10 models that consider multiple variables: the magnitude of benefits conferred on beneficiaries, the magnitude of costs incurred by benefactors, beneficiaries' perception of how much benefactors value their welfare, and beneficiaries' value for the welfare of their benefactors. Across both studies, only beneficiaries' change in social valuation for their benefactors consistently predicted gratitude. Results point to the need for further research and contribute to the growing literature linking cooperation, social emotions, and social valuation.

If it quacks like a duck: The by-product account of music still stands.

Discerning adaptations from by-products is a defining feature of evolutionary science. Mehr, Krasnow, Bryant, and Hagen posit that music is an adaptation that evolved to function as a credible signal. We counter this claim, as we are not convinced they have dispelled the possibility that music is an elaboration of extant features of language.

Considerations of the proximate mechanisms and ultimate functions of disgust will improve our understanding of cleansing effects.

To understand the consequences of cleansing, Lee and Schwarz favor a grounded procedures perspective over recently developed disgust theory. We believe that this position stems from three errors: (1) interpreting cleansing effects as broader than they are; (2) not detailing the proximate mechanisms underlying disgust; and (3) not detailing adaptive function versus system byproducts when developing the grounded procedures perspective.

Behavioral Immune Trade-Offs: Interpersonal Value Relaxes Social Pathogen Avoidance.

Behavioral-immune-system research has illuminated how people detect and avoid signs of infectious disease. But how do we regulate exposure to pathogens that produce no symptoms in their hosts? This research tested the proposition that estimates of interpersonal value are used for this task. The results of three studies (N = 1,694), each conducted using U.S. samples, are consistent with this proposition: People are less averse to engaging in infection-risky acts not only with friends relative to foes but also with honest and agreeable strangers relative to dishonest and disagreeable ones. Further, a continuous measure of how much a person values a target covaries with comfort with infection-risky acts with that target, even within relationship categories. Findings indicate that social prophylactic motivations arise not only from cues to infectiousness but also from interpersonal value. Consequently, pathogen transmission within social networks might be exacerbated by relaxed contamination aversions with highly valued social partners.

The architecture of human kin detection.

Evolved mechanisms for assessing genetic relatedness have been found in many species, but their existence in humans has been a matter of controversy. Here we report three converging lines of evidence, drawn from siblings, that support the hypothesis that kin detection mechanisms exist in humans. These operate by computing, for each familiar individual, a unitary regulatory variable (the kinship index) that corresponds to a pairwise estimate of genetic relatedness between self and other. The cues that the system uses were identified by quantitatively matching individual exposure to potential cues of relatedness to variation in three outputs relevant to the system's evolved functions: sibling altruism, aversion to personally engaging in sibling incest, and moral opposition to third party sibling incest. As predicted, the kin detection system uses two distinct, ancestrally valid cues to compute relatedness: the familiar other's perinatal association with the individual's biological mother, and duration of sibling coresidence.

The power of play: Innovations in Getting Active Summit 2011: a science panel proceedings report from the American Heart Association.

BACKGROUND: To examine the influence active-play video gaming (also referred to as exergaming, exertainment, and active gaming) might have on improving health-related skills, enhancing self-esteem and self-efficacy, promoting social support, and ultimately motivating positive changes in health behaviors, the American Heart Association convened The Power of Play: Innovations in Getting Active Summit. The summit, as well as a follow-up science panel, was hosted by the American Heart Association and Nintendo of America. METHODS AND RESULTS: The science panel discussed the current state of research on active-play video gaming and its potential to serve as a gateway experience that might motivate players to increase the amount and intensity of physical activity in their daily lives. The panel identified the need for continued research on the gateway concept and on other behavioral health outcomes that could result from active-play video games and considered how these games could potentially affect disparate populations. CONCLUSIONS: The summit represented an exciting first step in convening healthcare providers, behavioral researchers, and professionals from the active-play video game industry to discuss the potential health benefits of active-play video games. Research is needed to improve understanding of processes of behavior change with active games. Future games and technologies may be designed with the goal to optimize physical activity participation, increase energy expenditure, and effectively address the abilities and interests of diverse and targeted populations. The summit helped the participants gain an understanding of what is known, identified gaps in current research, and supported a dialogue for continued collaboration.

Kin affiliation across the ovulatory cycle: females avoid fathers when fertile.

A commonplace observation in humans is that close genetic relatives tend to avoid one another as sexual partners. Despite the growing psychological research on how antierotic attitudes develop toward relatives, few studies have focused on actual behavior. One prediction, stemming from parental investment theory, is that women should be more vigilant of reproduction-compromising behaviors, such as inbreeding, during times of peak fertility than during times of low fertility. Indeed, females of other species avoid interactions with male kin when fertile-but the corollary behavior in humans has yet to be explored. Here we fill this gap. Using duration and frequency of cell-phone calls, an objective behavioral measure that reflects motivations to interact socially, we show that women selectively avoid interactions with their fathers during peak fertility. Avoidance specifically targeted fathers, which rules out alternative explanations. These data suggest that psychological mechanisms underlying mating psychology regulate sexual avoidance behaviors, and in women they fluctuate according to fertility status.

A feel for disgust: tactile cues to pathogen presence.

One function of disgust is to act as a pathogen-avoidance system preventing contact with substances harbouring disease-causing organisms. Avoiding pathogens, however, requires systems for their detection. Whereas previous research on disgust has focused on visual and olfactory detection cues, one largely overlooked modality is touch. Here we examine whether tactile cues play a role in pathogen detection and activate the disgust response. Participants briefly touched and then rated stimuli varying along dimensions predicted to correlate with pathogen presence: moisture, temperature, and consistency. Results show that participants rated wet stimuli and stimuli resembling biological consistencies as more disgusting than dry stimuli and stimuli resembling inanimate consistencies, respectively. No main effect for temperature was found. We report on predicted interactions, the relationship between disgust ratings and perceived infection risk, and individual differences. Taken together, these data suggest that touch is an important modality providing information for disgust-related processes.

Experimental evidence that apologies promote forgiveness by communicating relationship value.

Robust evidence supports the importance of apologies for promoting forgiveness. Yet less is known about how apologies exert their effects. Here, we focus on their potential to promote forgiveness by way of increasing perceptions of relationship value. We used a method for directly testing these causal claims by manipulating both the independent variable and the proposed mediator. Namely, we use a 2 (Apology: yes vs. no) × 2 (Value: high vs. low) concurrent double-randomization design to test whether apologies cause forgiveness by affecting the same causal pathway as relationship value. In addition to supporting this causal claim, we also find that apologies had weaker effects on forgiveness when received from high-value transgressors, suggesting that the forgiveness-relevant information provided by apologies is redundant with relationship value. Taken together, these findings from a rigorous methodological paradigm help us parse out how apologies promote relationship repair.

The evolution of disgust for pathogen detection and avoidance.

The behavioral immune system posits that disgust functions to protect animals from pathogen exposure. Therefore, cues of pathogen risk should be a primary driver influencing variation in disgust. Yet, to our knowledge, neither the relationship between current pathogen risk and disgust, nor the correlation between objective and perceived pathogen risk have been addressed using ecologically valid measures in a global sample. The current article reports two studies addressing these gaps. In Study 1, we include a global sample (n = 361) and tested the influence of both perceived pathogen exposure and an objective measure of pathogen risk-local communicable infectious disease mortality rates-on individual differences in pathogen and sexual disgust sensitivities. In Study 2, we first replicate Study 1's analyses in another large sample (n = 821), targeting four countries (US, Italy, Brazil, and India); we then replaced objective and perceived pathogen risk with variables specific to the SARS-CoV-2 pandemic. In Study 1, both local infection mortality rates and perceived infection exposure predicted unique variance in pathogen and sexual disgust. In Study 2, we found that perceived infection exposure positively predicted sexual disgust, as predicted. When substituting perceived and objective SARS-CoV-2 risk in our models, perceived risk of contracting SARS-CoV-2 positively predicted pathogen and sexual disgust, and state case rates negatively predicted pathogen disgust. Further, in both studies, objective measures of risk (i.e., local infection mortality and SARS-CoV-2 rates) positively correlated with subjective measures of risk (i.e., perceived infection exposure and perceived SARS-CoV-2 risk). Ultimately, these results provide two pieces of foundational evidence for the behavioral immune system: 1) perceptions of pathogen risk accurately assay local, objective mortality risk across countries, and 2) both perceived and objective pathogen risk explain variance in disgust levels.

Forgiveness takes place on an attitudinal continuum from hostility to friendliness: Toward a closer union of forgiveness theory and measurement.

Researchers commonly conceptualize forgiveness as a rich complex of psychological changes involving attitudes, emotions, and behaviors. Psychometric work with the measures developed to capture this conceptual richness, however, often points to a simpler picture of the psychological dimensions in which forgiveness takes place. In an effort to better unite forgiveness theory and measurement, we evaluate several psychometric models for common measures of forgiveness. In doing so, we study people from the United States and Japan to understand forgiveness in both nonclose and close relationships. In addition, we assess the predictive utility of these models for several behavioral outcomes that traditionally have been linked to forgiveness motives. Finally, we use the methods of item response theory, which place person abilities and item responses on the same metric and, thus, help us draw psychological inferences from the ordering of item difficulties. Our results highlight models based on correlated factors models and bifactor (S-1) models. The bifactor (S-1) model evinced particular utility: Its general factor consistently predicts variation in relevant criterion measures, including 4 different experimental economic games (when played with a transgressor), and also suffuses a second self-report measure of forgiveness. Moreover, the general factor of the bifactor (S-1) model identifies a single psychological dimension that runs from hostility to friendliness while also pointing to other sources of variance that may be conceived of as method factors. Taken together, these results suggest that forgiveness can be usefully conceptualized as prosocial change along a single attitudinal continuum that ranges from hostility to friendliness. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Microbes, mating, and morality: individual differences in three functional domains of disgust.

What is the function of disgust? Whereas traditional models have suggested that disgust serves to protect the self or neutralize reminders of our animal nature, an evolutionary perspective suggests that disgust functions to solve 3 qualitatively different adaptive problems related to pathogen avoidance, mate choice, and social interaction. The authors investigated this 3-domain model of disgust across 4 studies and examined how sensitivity to these functional domains relates to individual differences in other psychological constructs. Consistent with their predictions, factor analyses demonstrated that disgust sensitivity partitions into domains related to pathogens, sexuality, and morality. Further, sensitivity to the 3 domains showed predictable differentiation based on sex, perceived vulnerability to disease, psychopathic tendencies, and Big 5 personality traits. In exploring these 3 domains of disgust, the authors introduce a new measure of disgust sensitivity. Appreciation of the functional heterogeneity of disgust has important implications for research on individual differences in disgust sensitivity, emotion, clinical impairments, and neuroscience.

What evidence is required to determine whether infants infer the kinship of third parties? A commentary on Spokes and Spelke (2017).

Research into the cognitive capacities of infants has revealed a rich assortment of competencies that help to structure inferences across multiple content domains. Despite these advances, researchers have paid relatively little attention to a domain crucial to social life: kinship. One recent exception is a set of studies by Spokes and Spelke (2017), who report evidence that 15 to 18-month-old infants expect social affiliation between two babies receiving care from the same adult. The experiments reported by Spokes and Spelke raise the key question of whether infants harbor intuitions regarding kinship-and provide tantalizing hints that they do. But determining whether the infant inferences found in these experiments in fact do implicate a kin-specific psychology is not straightforward, as kinship and social group membership overlap. Researchers need a set of criteria for ascertaining whether individuals (preverbal infants in particular but also children and adults alike) infer kinship-the likely genetic relatedness-between agents based on interactions with a common 3rd party and then use this information to guide expectations of behavior. Here, we consider the nature of evidence that would be needed to establish in principle that infants make inferences specific to kinship. In doing so, we link the developmental literature on infant social cognition to adult kin detection research, which has previously grappled with the question of what evidentiary standards reasonably establish the presence of kin-specific inferences. In light of prior empirical and theoretical work, we advance four criteria for establishing the presence of tacit knowledge of kinship, assess the extent to which the studies presented by S&S meet these criteria, and use the criteria to inform and spark directions for future research.

Sexual Disgust Trumps Pathogen Disgust in Predicting Voter Behavior During the 2016 U.S. Presidential Election.

Why is disgust sensitivity associated with socially conservative political views? Is it because socially conservative ideologies mitigate the risks of infectious disease, whether by promoting out-group avoidance or by reinforcing norms that sustain antipathogenic practices? Or might it be because socially conservative ideologies promote moral standards that advance a long-term, as opposed to a short-term, sexual strategy? Recent attempts to test these two explanations have yielded differing results and conflicting interpretations. Here, we contribute to the literature by examining the relationship between disgust sensitivity and political orientation, political party affiliation, and an often overlooked outcome-actual voter behavior. We focus on voter behavior and affiliation for the 2016 U.S. presidential election to determine whether pathogen or sexual disgust better predicts socially conservative ideology. Although many prominent aspects of Donald Trump's campaign-particularly his anti-foreign message-align with the pathogen-avoidance model of conservatism, we found that pathogen-related disgust sensitivity exerted no influence on political ideology, political party affiliation, or voter behavior, after controlling for sexual disgust sensitivity. In contrast, sexual disgust sensitivity was associated with increased odds of voting for Donald Trump versus each other major presidential candidate, as well as with increased odds of affiliating with the Republican versus the Democratic or Libertarian parties. In fact, for every unit increase in sexual disgust sensitivity, the odds of a participant voting for Trump versus Clinton increased by approximately 30%. It seems, then, that sexual disgust trumps pathogen disgust in predicting socially conservative voting behavior.

Consumption, contact and copulation: how pathogens have shaped human psychological adaptations.

Disgust is an emotion intimately linked to pathogen avoidance. Building on prior work, we suggest disgust is an output of programmes that evolved to address three separate adaptive problems: what to eat, what to touch and with whom to have sex. We briefly discuss the architecture of these programmes, specifying their perceptual inputs and the contextual factors that enable them to generate adaptive and flexible behaviour. We propose that our sense of disgust is the result of these programmes and occurs when information-processing circuitries assess low expected values of consumption, low expected values of contact or low expected sexual values. This conception of disgust differs from prior models in that it dissects pathogen-related selection pressures into adaptive problems related to consumption and contact rather than assuming just one pathogen disgust system, and it excludes moral disgust from the domain of disgust proper. Instead, we illustrate how low expected values of consumption and contact as well as low expected sexual values can be used by our moral psychology to provide multiple causal links between disgust and morality.This article is part of the Theo Murphy meeting issue 'Evolution of pathogen and parasite avoidance behaviours'.

Opposition to Inbreeding Between Close Kin Reflects Inclusive Fitness Costs.

Due to the intense selection pressure against inbreeding, humans are expected to possess psychological adaptations that regulate mate choice and avoid inbreeding. From a gene's-eye perspective, there is little difference in the evolutionary costs between situations where an individual him/herself is participating in inbreeding and inbreeding among other close relatives. The difference is merely quantitative, as fitness can be compromised via both routes. The question is whether humans are sensitive to the direct as well as indirect costs of inbreeding. Using responses from a large population-based sample (27,364 responses from 2,353 participants), we found that human motivations to avoid inbreeding closely track the theoretical costs of inbreeding as predicted by inclusive fitness theory. Participants were asked to select in a forced choice paradigm, which of two acts of inbreeding with actual family members they would want to avoid most. We found that the estimated fitness costs explained 83.6% of participant choices. Importantly, fitness costs explained choices also when the self was not involved. We conclude that humans intuit the indirect fitness costs of mating decisions made by close family members and that psychological inbreeding avoidance mechanisms extend beyond self-regulation.

Coresidence duration and cues of maternal investment regulate sibling altruism across cultures.

Genetic relatedness is a fundamental determinant of social behavior across species. Over the last few decades, researchers have been investigating the proximate psychological mechanisms that enable humans to assess their genetic relatedness to others. Much of this work has focused on identifying cues that predicted relatedness in ancestral environments and examining how they regulate kin-directed behaviors. Despite progress, many basic questions remain unanswered. Here we address three of these questions. First, we examine the replicability of the effect of two association-based cues to relatedness-maternal perinatal association (MPA) and coresidence duration-on sibling-directed altruism. MPA, the observation of a newborn being cared for by one's mother, strongly signals relatedness, but is only available to the older sibling in a sib-pair. Younger siblings, to whom the MPA cue is not available, appear to fall back on the duration of their coresidence with an older sibling. Second, we determine whether the effects of MPA and coresidence duration on sibling-directed altruism obtain across cultures. Last, we explore whether paternal perinatal association (PPA) informs sibship. Data from six studies conducted in California, Hawaii, Dominica, Belgium, and Argentina support past findings regarding the role of MPA and coresidence duration as cues to siblingship. By contrast, PPA had no effect on altruism. We report on levels of altruism toward full, half, and step siblings, and discuss the role alternate cues might play in discriminating among these types of siblings. (PsycINFO Database Record