Pub Date : 2025-11-18DOI: 10.1016/j.evolhumbehav.2025.106779
Terence Kealey
Human kissing appears to be part of a constellation of sexually- and socially-coevolved traits that include body hairlessness, art, continually-growing head hair, acne vulgaris and keloid scarring.
{"title":"The co-evolution in humans by sexual and social selection of kissing, body hairlessness, art, continually-growing head hair, acne vulgaris and keloid scarring","authors":"Terence Kealey","doi":"10.1016/j.evolhumbehav.2025.106779","DOIUrl":"10.1016/j.evolhumbehav.2025.106779","url":null,"abstract":"<div><div>Human kissing appears to be part of a constellation of sexually- and socially-coevolved traits that include body hairlessness, art, continually-growing head hair, acne vulgaris and keloid scarring.</div></div>","PeriodicalId":55159,"journal":{"name":"Evolution and Human Behavior","volume":"47 1","pages":"Article 106779"},"PeriodicalIF":3.2,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-11DOI: 10.1016/j.evolhumbehav.2025.106803
Tiffany S. Leung, Elizabeth A. Simpson
Lassitude—characterized by drooping eyelids, pale and slightly parted lips, and drooping corners of the mouth—is an emotional expression exhibited when people are sick. Here, we tested the hypothesis that there may be individual differences in the ability to recognize lassitude facial expressions. Adults from an undergraduate subject pool in the U.S. (N = 280) viewed images of healthy faces and the same people's faces when they were sick with a naturally occurring contagious illness, rating them on six dimensions theorized to index latent lassitude perception: safety, healthiness, approachability, alertness, social interest, and positivity. We found each dimension loaded positively onto latent lassitude perception, consistent with our hypothesis that these dimensions tap unique but related constructs. Participants' sex predicted their latent lassitude perception, with females showing higher accuracy than males. Our findings suggest there are sex differences in sick face perception, much like the perception of other nonverbal expressions. This is the first study, to our knowledge, to discover a female advantage in recognizing natural lassitude expressions. We discuss possible evolutionary mechanisms, such as the Primary Caretaker Hypothesis, and implications for public health.
{"title":"Individual differences in sick face sensitivity: females are more sensitive to lassitude facial expressions than males","authors":"Tiffany S. Leung, Elizabeth A. Simpson","doi":"10.1016/j.evolhumbehav.2025.106803","DOIUrl":"10.1016/j.evolhumbehav.2025.106803","url":null,"abstract":"<div><div>Lassitude—characterized by drooping eyelids, pale and slightly parted lips, and drooping corners of the mouth—is an emotional expression exhibited when people are sick. Here, we tested the hypothesis that there may be individual differences in the ability to recognize lassitude facial expressions. Adults from an undergraduate subject pool in the U.S. (<em>N</em> = 280) viewed images of healthy faces and the same people's faces when they were sick with a naturally occurring contagious illness, rating them on six dimensions theorized to index latent lassitude perception: safety, healthiness, approachability, alertness, social interest, and positivity. We found each dimension loaded positively onto latent lassitude perception, consistent with our hypothesis that these dimensions tap unique but related constructs. Participants' sex predicted their latent lassitude perception, with females showing higher accuracy than males. Our findings suggest there are sex differences in sick face perception, much like the perception of other nonverbal expressions. This is the first study, to our knowledge, to discover a female advantage in recognizing natural lassitude expressions. We discuss possible evolutionary mechanisms, such as the Primary Caretaker Hypothesis, and implications for public health.</div></div>","PeriodicalId":55159,"journal":{"name":"Evolution and Human Behavior","volume":"47 1","pages":"Article 106803"},"PeriodicalIF":3.2,"publicationDate":"2025-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145520361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-08DOI: 10.1016/j.evolhumbehav.2025.106783
Lisa M. Bohon, Sophia Sinclair, Raquel R. Medeiros-Tejomaya, Jessica Hamel, Alexandra H.B. Hock
The purpose of this study was to investigate childhood ecology before the age of 10 and adult psychosocial Life History (LH) traits as predictors of adult mating effort. College women (N = 875) volunteered in an online Qualtrics study. SEM analysis showed that faster life psychosocial traits explained 22.2 % of the relation between the childhood microsystem and mating effort. Women who experienced a disordered microsystem (childhood trauma, parental disengagement, parental cohabitation with an unrelated adult, and crime in their neighborhood) were more likely to exhibit adult faster LH personality traits such as psychopathy, impulsivity, resource control, tendencies, and neuroticism. These personality traits were also associated with a greater number of lifetime sexual partners, shorter-term mating orientation, and greater intention to engage in risky sexual behaviors. In addition, a disordered microsystem, and perceived resource insecurity related to having more lifetime sexual partners, shorter-term mating orientation, and greater endorsement of future risky sexual behaviors.
{"title":"Using SEM to test the associations among women's childhood ecology, adult psychosocial life history traits, and mating effort","authors":"Lisa M. Bohon, Sophia Sinclair, Raquel R. Medeiros-Tejomaya, Jessica Hamel, Alexandra H.B. Hock","doi":"10.1016/j.evolhumbehav.2025.106783","DOIUrl":"10.1016/j.evolhumbehav.2025.106783","url":null,"abstract":"<div><div>The purpose of this study was to investigate childhood ecology before the age of 10 and adult psychosocial Life History (LH) traits as predictors of adult mating effort. College women (<em>N</em> = 875) volunteered in an online Qualtrics study. SEM analysis showed that faster life psychosocial traits explained 22.2 % of the relation between the childhood microsystem and mating effort. Women who experienced a disordered microsystem (childhood trauma, parental disengagement, parental cohabitation with an unrelated adult, and crime in their neighborhood) were more likely to exhibit adult faster LH personality traits such as psychopathy, impulsivity, resource control, tendencies, and neuroticism. These personality traits were also associated with a greater number of lifetime sexual partners, shorter-term mating orientation, and greater intention to engage in risky sexual behaviors. In addition, a disordered microsystem, and perceived resource insecurity related to having more lifetime sexual partners, shorter-term mating orientation, and greater endorsement of future risky sexual behaviors.</div></div>","PeriodicalId":55159,"journal":{"name":"Evolution and Human Behavior","volume":"47 1","pages":"Article 106783"},"PeriodicalIF":3.2,"publicationDate":"2025-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145520362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-05DOI: 10.1016/j.evolhumbehav.2025.106750
Camille Rioux , Annie E. Wertz
Watching what others put in their mouths is a powerful way to learn what to eat. Yet human diets and eating behaviors are complicated, and not everything that goes into another person's mouth is food: The fusilli is edible, but the fork is not. Therefore, some selectivity is necessary to guide social learning processes about food. Here we examined 6-month-old infants' expectations about what kinds of entities are likely to be edible using a violation-of-expectation setup in which infants viewed an actor eating from two different items. We hypothesized that infants may have selective edibility expectations about plants, and in particular fruits, that stem from humans' long evolutionary history of foraging wild plant foods and specialization in higher caloric density plant parts. In Experiment 1 (N = 40), we found that infants expect plants, relative to feature-matched artifacts, to be edible, replicating a previous finding [Wertz & Wynn, 2014a]. In Experiments 2 (N = 40) and 3 (N = 39), we examined, for the first time, whether selective expectations about plant edibility are tied to particular plant parts. Our results showed that infants do not differentially expect leaves to be edible, but our results for fruits were inconclusive. Taken together, these findings suggest that infants differentially expect plants to be edible and that these expectations appear to be strongest for whole plants.
{"title":"Expectations about plant edibility in 6-month-old infants","authors":"Camille Rioux , Annie E. Wertz","doi":"10.1016/j.evolhumbehav.2025.106750","DOIUrl":"10.1016/j.evolhumbehav.2025.106750","url":null,"abstract":"<div><div>Watching what others put in their mouths is a powerful way to learn what to eat. Yet human diets and eating behaviors are complicated, and not everything that goes into another person's mouth is food: The fusilli is edible, but the fork is not. Therefore, some selectivity is necessary to guide social learning processes about food. Here we examined 6-month-old infants' expectations about what kinds of entities are likely to be edible using a violation-of-expectation setup in which infants viewed an actor eating from two different items. We hypothesized that infants may have selective edibility expectations about plants, and in particular fruits, that stem from humans' long evolutionary history of foraging wild plant foods and specialization in higher caloric density plant parts. In Experiment 1 (<em>N</em> = 40), we found that infants expect plants, relative to feature-matched artifacts, to be edible, replicating a previous finding [<span><span>Wertz & Wynn, <strong>2014a</strong></span></span>]. In Experiments 2 (<em>N</em> = 40) and 3 (<em>N</em> = 39), we examined, for the first time, whether selective expectations about plant edibility are tied to particular plant parts. Our results showed that infants do not differentially expect leaves to be edible, but our results for fruits were inconclusive. Taken together, these findings suggest that infants differentially expect plants to be edible and that these expectations appear to be strongest for whole plants.</div></div>","PeriodicalId":55159,"journal":{"name":"Evolution and Human Behavior","volume":"47 1","pages":"Article 106750"},"PeriodicalIF":3.2,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145467760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-05DOI: 10.1016/j.evolhumbehav.2025.106789
Kristen K. Knowles
{"title":"Zombie Theories and the Quest for Consilience: A Critical Review of Hertler et al.’s The Evolution of Political Ideology","authors":"Kristen K. Knowles","doi":"10.1016/j.evolhumbehav.2025.106789","DOIUrl":"10.1016/j.evolhumbehav.2025.106789","url":null,"abstract":"","PeriodicalId":55159,"journal":{"name":"Evolution and Human Behavior","volume":"47 1","pages":"Article 106789"},"PeriodicalIF":3.2,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145467783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-03DOI: 10.1016/j.evolhumbehav.2025.106800
Konrad Rudnicki , Olgierd Borowiecki , Karolien Poels , Bianca Beersma , Wei Peng , Ed Sleebos , Charlotte De Backer
Dark Triad traits – psychopathy, Machiavellianism, and narcissism – raise evolutionary questions about the mechanisms enabling social exploitation in individuals with lower empathy. While empathy likely evolved to sustain cooperation and social bonds, less effective cognitive empathy among individuals with Dark Triad traits may reflect trade-offs favoring self-serving strategies over prosocial engagement. One such trade-off may involve impairments in agency detection sensitivity, a cognitive process foundational to recognizing others as intentional agents with independent goals and emotions. These impairments could disrupt the ability to engage in perspective-taking, a critical component of cognitive empathy, thereby facilitating manipulative and exploitative behaviors.
A preregistered online study involving N = 604 participants recruited via the Prolific platform entailed assessing cognitive empathy performance (Multifaceted Empathy Test), dehumanization propensity, Dark Triad traits, and agency detection sensitivity using a specialized motion task. Results revealed that psychopathy was associated with lower cognitive empathy and greater dehumanization. However, variation in agency detection sensitivity did not explain this association directly. Instead, correlation between psychopathy and cognitive empathy grew even more negative in individuals with low levels of agency detection sensitivity.
These findings suggest that worse agency detection may accompany existing empathy attenuation in individuals high in psychopathy, which could be linked to even higher difficulty of engaging in prosocial behavior for them. This supports the notion of a deficit driven strategy, whereby those who score high on psychopathy might conserve cognitive resources by bypassing effortful moral reasoning and empathy, particularly when such engagement would be impeded by other, co-existing down-regulated cognitive processes.
{"title":"Cognitive empathy and dehumanization co-vary with dark triad traits and agency detection sensitivity","authors":"Konrad Rudnicki , Olgierd Borowiecki , Karolien Poels , Bianca Beersma , Wei Peng , Ed Sleebos , Charlotte De Backer","doi":"10.1016/j.evolhumbehav.2025.106800","DOIUrl":"10.1016/j.evolhumbehav.2025.106800","url":null,"abstract":"<div><div>Dark Triad traits – psychopathy, Machiavellianism, and narcissism – raise evolutionary questions about the mechanisms enabling social exploitation in individuals with lower empathy. While empathy likely evolved to sustain cooperation and social bonds, less effective cognitive empathy among individuals with Dark Triad traits may reflect trade-offs favoring self-serving strategies over prosocial engagement. One such trade-off may involve impairments in agency detection sensitivity, a cognitive process foundational to recognizing others as intentional agents with independent goals and emotions. These impairments could disrupt the ability to engage in perspective-taking, a critical component of cognitive empathy, thereby facilitating manipulative and exploitative behaviors.</div><div>A preregistered online study involving <em>N</em> = 604 participants recruited via the Prolific platform entailed assessing cognitive empathy performance (Multifaceted Empathy Test), dehumanization propensity, Dark Triad traits, and agency detection sensitivity using a specialized motion task. Results revealed that psychopathy was associated with lower cognitive empathy and greater dehumanization. However, variation in agency detection sensitivity did not explain this association directly. Instead, correlation between psychopathy and cognitive empathy grew even more negative in individuals with low levels of agency detection sensitivity.</div><div>These findings suggest that worse agency detection may accompany existing empathy attenuation in individuals high in psychopathy, which could be linked to even higher difficulty of engaging in prosocial behavior for them. This supports the notion of a deficit driven strategy, whereby those who score high on psychopathy might conserve cognitive resources by bypassing effortful moral reasoning and empathy, particularly when such engagement would be impeded by other, co-existing down-regulated cognitive processes.</div></div>","PeriodicalId":55159,"journal":{"name":"Evolution and Human Behavior","volume":"47 1","pages":"Article 106800"},"PeriodicalIF":3.2,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145467784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-31DOI: 10.1016/j.evolhumbehav.2025.106777
Remco Kort
The human microbiota —the collection of microorganisms living on and inside the body—plays a fundamental role in human health. While diet, genetics, and environment strongly shape microbiota composition, social interactions may also influence the microbial communities associated with the human body. Intimate kissing is a widespread human behaviour that involves close contact and exchange of saliva, providing an opportunity for direct microbial transmission between individuals. This article explores the hypothesis that intimate kissing can induce a reinforcing cycle – a positive feedback loop - that shapes and stabilizes the oral microbiota of partners over time. Neurobiological pathways, including the gut microbiota–brain axis, might reinforce this feedback loop. Current evidence is synthesized and a study design outlined to explore how kissing may lead to sustained microbial sharing and potential systemic effects.
{"title":"A sweet kiss with a bacterial touch: a potential positive feedback loop involved in shaping the oral microbiota","authors":"Remco Kort","doi":"10.1016/j.evolhumbehav.2025.106777","DOIUrl":"10.1016/j.evolhumbehav.2025.106777","url":null,"abstract":"<div><div>The human microbiota —the collection of microorganisms living on and inside the body—plays a fundamental role in human health. While diet, genetics, and environment strongly shape microbiota composition, social interactions may also influence the microbial communities associated with the human body. Intimate kissing is a widespread human behaviour that involves close contact and exchange of saliva, providing an opportunity for direct microbial transmission between individuals. This article explores the hypothesis that intimate kissing can induce a reinforcing cycle – a positive feedback loop - that shapes and stabilizes the oral microbiota of partners over time. Neurobiological pathways, including the gut microbiota–brain axis, might reinforce this feedback loop. Current evidence is synthesized and a study design outlined to explore how kissing may lead to sustained microbial sharing and potential systemic effects.</div></div>","PeriodicalId":55159,"journal":{"name":"Evolution and Human Behavior","volume":"47 1","pages":"Article 106777"},"PeriodicalIF":3.2,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145420291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-29DOI: 10.1016/j.evolhumbehav.2025.106790
Patrick K. Durkee , Peyton A. Graves , Nina N. Rodriguez
From an adaptationist perspective, personality constructs can be viewed as behavioral summaries reflecting interindividual variation in evolved psychological mechanisms. In this study, we investigate how differences in the functioning of competitor derogation mechanisms—specifically differences in accuracy of derogation tactic effectiveness estimates—relate to variation in personality constructs, including the Dark Triad, Big Five, and emotional intelligence. We first established criterion ratings for a large set of competitor derogation tactics (k = 445) using an online U.S. sample (n = 320). In a second online U.S. sample (N = 355), we then estimated associations between individual differences in competitor derogation accuracy and self-reported personality constructs using Bayesian multilevel models. We found that higher Dark Triad scores were associated with lower competitor derogation accuracy at the zero-order level, but unique variance in Machiavellianism predicted greater accuracy. Competitor derogation accuracy was also positively associated with emotional intelligence, conscientiousness, and agreeableness, and negatively associated with extraversion. These findings illustrate one way an adaptationist framework can help link personality variation to evolved psychological mechanisms.
{"title":"Toward a mechanistic account of personality: A case study of competitor derogation accuracy and the dark triad","authors":"Patrick K. Durkee , Peyton A. Graves , Nina N. Rodriguez","doi":"10.1016/j.evolhumbehav.2025.106790","DOIUrl":"10.1016/j.evolhumbehav.2025.106790","url":null,"abstract":"<div><div>From an adaptationist perspective, personality constructs can be viewed as behavioral summaries reflecting interindividual variation in evolved psychological mechanisms. In this study, we investigate how differences in the functioning of competitor derogation mechanisms—specifically differences in accuracy of derogation tactic effectiveness estimates—relate to variation in personality constructs, including the Dark Triad, Big Five, and emotional intelligence. We first established criterion ratings for a large set of competitor derogation tactics (<em>k</em> = 445) using an online U.S. sample (<em>n</em> = 320). In a second online U.S. sample (<em>N</em> = 355), we then estimated associations between individual differences in competitor derogation accuracy and self-reported personality constructs using Bayesian multilevel models. We found that higher Dark Triad scores were associated with lower competitor derogation accuracy at the zero-order level, but unique variance in Machiavellianism predicted greater accuracy. Competitor derogation accuracy was also positively associated with emotional intelligence, conscientiousness, and agreeableness, and negatively associated with extraversion. These findings illustrate one way an adaptationist framework can help link personality variation to evolved psychological mechanisms.</div></div>","PeriodicalId":55159,"journal":{"name":"Evolution and Human Behavior","volume":"47 1","pages":"Article 106790"},"PeriodicalIF":3.2,"publicationDate":"2025-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145420290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-27DOI: 10.1016/j.evolhumbehav.2025.106786
Martina Francesconi , Alice Galotti , Yannick Jadoul , Federico Giovannini , Andrea Ravignani , Elisabetta Palagi
Nonverbal communication plays a central role in human sexual interactions, enhancing sexual satisfaction and perceived partner connectedness. Here, we investigate the potential evolutionary roots of visual communication by examining the role of facial displays in sexual interactions in bonobos (Pan paniscus), a species in which - unlike many others - sexuality serves both reproductive and social functions. Using high-resolution temporal analyses, we tested whether variations in the rate of the oscillatory movements during sex (a proxy for sexual stimulation intensity) are associated with the exchange of facial expressions, specifically silent bared-teeth (SBT) displays and rapid facial mimicry (RFM). Analyses of sexual sessions free from interference by third-parties revealed that the offset of unilateral SBTs was not followed by a significant decrease in the oscillatory movement rates, whereas the termination of RFM consistently triggered a decline in sexual stimulation. Restricted temporal windows surrounding RFM cessation further confirmed that disruption of facial mimicry by even one partner suffices to decrease stimulation intensity. These results indicate that RFM, rather than passive observation of a partner's expression, marks the peak of sexual stimulation and reflects fine-grained socio-emotional coordination between partners. Our findings suggest that rapid facial exchanges during sexual interactions in bonobos may represent an evolutionarily conserved mechanism linking nonverbal communication and coordination in social actions. This work provides comparative insights into the communicative functions of facial expressions, highlighting parallels between humans and one of our closest phylogenetic relatives.
{"title":"SEX in bonobos: The intensity of sexual stimulation sharply drops after facial mimicry","authors":"Martina Francesconi , Alice Galotti , Yannick Jadoul , Federico Giovannini , Andrea Ravignani , Elisabetta Palagi","doi":"10.1016/j.evolhumbehav.2025.106786","DOIUrl":"10.1016/j.evolhumbehav.2025.106786","url":null,"abstract":"<div><div>Nonverbal communication plays a central role in human sexual interactions, enhancing sexual satisfaction and perceived partner connectedness. Here, we investigate the potential evolutionary roots of visual communication by examining the role of facial displays in sexual interactions in bonobos (<em>Pan paniscus</em>), a species in which - unlike many others - sexuality serves both reproductive and social functions. Using high-resolution temporal analyses, we tested whether variations in the rate of the oscillatory movements during sex (a proxy for sexual stimulation intensity) are associated with the exchange of facial expressions, specifically silent bared-teeth (SBT) displays and rapid facial mimicry (RFM). Analyses of sexual sessions free from interference by third-parties revealed that the offset of unilateral SBTs was not followed by a significant decrease in the oscillatory movement rates, whereas the termination of RFM consistently triggered a decline in sexual stimulation. Restricted temporal windows surrounding RFM cessation further confirmed that disruption of facial mimicry by even one partner suffices to decrease stimulation intensity. These results indicate that RFM, rather than passive observation of a partner's expression, marks the peak of sexual stimulation and reflects fine-grained socio-emotional coordination between partners. Our findings suggest that rapid facial exchanges during sexual interactions in bonobos may represent an evolutionarily conserved mechanism linking nonverbal communication and coordination in social actions. This work provides comparative insights into the communicative functions of facial expressions, highlighting parallels between humans and one of our closest phylogenetic relatives.</div></div>","PeriodicalId":55159,"journal":{"name":"Evolution and Human Behavior","volume":"47 1","pages":"Article 106786"},"PeriodicalIF":3.2,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145369816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-24DOI: 10.1016/j.evolhumbehav.2025.106785
Kai Wen Zhou , Adam Baimel , Cindel J.M. White
Punishment and the threat thereof can help enforce social norms, but enacting punishment is often costly. To avoid these costs, individuals may prefer to offload the responsibility of punishment to others or to cultural institutions. We propose that shared beliefs about supernatural punishment contribute to minimizing the costs of interpersonal punishment by allowing people to offload punishment to supernatural entities. In a Third Party Punishment Game, we specifically test in a pre-registered experiment (N = 1603 Americans and Singaporeans adults, recruited through Qualtrics' online panels) whether thinking about karma (a supernatural force that punishes misdeeds) reduces punishment. Results confirm that being prompted to consider karma reduces inclinations to punish selfishness in a Third Party Punishment Game. A second pre-registered study using a subtler prime of karma replicated this effect. These findings suggest that karma beliefs may have played a role in the cultural evolution of human cooperation by reducing the costs of human norm enforcement while maintaining incentives for prosocial behaviour through the threat of supernatural punishment.
{"title":"Offloading punishment to karma: Thinking about karma reduces the punishment of transgressors","authors":"Kai Wen Zhou , Adam Baimel , Cindel J.M. White","doi":"10.1016/j.evolhumbehav.2025.106785","DOIUrl":"10.1016/j.evolhumbehav.2025.106785","url":null,"abstract":"<div><div>Punishment and the threat thereof can help enforce social norms, but enacting punishment is often costly. To avoid these costs, individuals may prefer to offload the responsibility of punishment to others or to cultural institutions. We propose that shared beliefs about supernatural punishment contribute to minimizing the costs of interpersonal punishment by allowing people to offload punishment to supernatural entities. In a Third Party Punishment Game, we specifically test in a pre-registered experiment (<em>N</em> = 1603 Americans and Singaporeans adults, recruited through Qualtrics' online panels) whether thinking about karma (a supernatural force that punishes misdeeds) reduces punishment. Results confirm that being prompted to consider karma reduces inclinations to punish selfishness in a Third Party Punishment Game. A second pre-registered study using a subtler prime of karma replicated this effect. These findings suggest that karma beliefs may have played a role in the cultural evolution of human cooperation by reducing the costs of human norm enforcement while maintaining incentives for prosocial behaviour through the threat of supernatural punishment.</div></div>","PeriodicalId":55159,"journal":{"name":"Evolution and Human Behavior","volume":"46 6","pages":"Article 106785"},"PeriodicalIF":3.2,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145361885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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