Social Partners Research Articles

Infants' Expectations for Helping in Imitators.

Human infants seem to make positive social inferences about individuals who imitate others. In three preregistered experiments we test if these inferences include an expectation that imitators will be helpful, and also ask if the inferences infants make are about imitators' dispositions or primarily about their relationships. In each experiment 8- to 9-month-old infants saw one individual imitate, and another individual not imitate, the same target social partner. When the imitator and non-imitator had the opportunity to help the target individual they had previously interacted with, infants looked longer when the non-imitator helped than when the imitator helped. However, when the potential recipient of help was a new social partner, infants' looking did not differ when the imitator or non-imitator helped. Overall, these results support the hypothesis that infants perceive imitation as prosocial or affiliative and thus expect imitators to be helpful. However, these expectations are limited to inferences about a specific prosocial relationship between the imitator and their target.

Children's social preference for teachers versus peers in autism inclusion classrooms: An objective perspective.

In inclusive preschools, children with autism spectrum disorder (ASD) and other developmental disabilities (DD) are less socially engaged with peers than are typically developing (TD) children. However, there is limited objective information describing how children with ASD engage with teachers, or how teacher engagement compares to engagement with peers. We tracked over 750 hours' worth of children's (N = 77; NASD = 24, NDD = 23, NTD = 30; Mage = 43.98 months) and teachers' (N = 12) locations and orientations across eight inclusion preschool classrooms to quantify child-teacher and child-peer social preference. Social approach velocity and time in social contact were computed for each child and compared across social partners to index children's preference for teachers over peers. Children with ASD approached teachers--but not peers-more quickly than children with TD, and children with ASD were approached more quickly by teachers and more slowly by peers than children with TD. Children with ASD spent less time in social contact with peers and did not differ from children with TD in their time in social contact with teachers. Overall, children with ASD showed a greater preference for approaching, being approached by, and being in social contact with teachers (relative to peers) than children with TD. No significant differences emerged between children with DD and children with TD. In conclusion, children with ASD exhibited a stronger preference for engaging with teachers over peers, re-emphasizing the need for classroom-based interventions that support the peer interactions of children with ASD.

Moral, conventional, personal: reasons for action as dimensions of normativity

ABSTRACT Human life is infused with different kinds of normativity (e.g. instrumental, epistemic, conventional, moral). Different theorists have proposed vastly differing views on how to conceptualize the different kinds of normativity. Whereas social domain theorists have asserted that moral, conventional, and personal kinds of normativity constitute distinct thematic domains and are viewed as such even by young children, other theorists have denied that moral and nonmoral kinds of normativity are thematically distinguishable. The current paper proposes a third approach that may show a way out of the controversy. Instead of viewing normative issues as belonging to one or more distinct thematic domains, it would be more accurate, both philosophically and psychologically speaking, to recognize that any given action may be grounded in multiple, non-exclusive reasons for action. Moral, conventional, and personal reasons for action may be defined in terms of what one believes one can respectively justify to all rational interlocutors, particular social partners, and oneself. The three kinds of reasons for action may accordingly be visualized as dimensions of normativity that together comprise a three-dimensional coordinate “space of reasons.” To illustrate the dimensions approach, 16 examples are given of actions whose values vary independently on each of the three dimensions.

I can’t feel your face: callous-unemotional traits, social anxiety, and approach-avoidance behaviour in conduct disorder

Background and objectivesConduct disorders are associated with deficits in interpersonal behaviour. Both, callous-unemotional traits and social anxiety are often elevated in patients with conduct disorder and are associated with aggressive approach or disproportional avoidance. Previous studies have focused mainly on questionnaire reports of interpersonal behaviour, whereas direct explicit and implicit interpersonal behaviour in social contexts has not been considered sufficiently. Therefore, explicit and implicit interpersonal behaviour were investigated in children and adolescents with conduct disorder in the current study.MethodsForty male adolescent inpatients with conduct disorder and 30 typically developing controls (Mage = 12.5, SD = 1.39) took part in a virtual reality task in which they approached virtual agemates, displaying different facial expressions under the pretext of a cover story while interpersonal distance and walking speed were assessed (indirect condition). In addition, they were asked to move to a comfortable distance for conversation toward the agent (direct condition). Callous-unemotional traits and social anxiety were assessed via questionnaires.ResultsIn the indirect condition, no differences between the groups emerged. In the direct condition, typically developing children adjusted their interpersonal distance to the respective expression that the virtual classmate displayed. They showed significantly greater interpersonal distances to angry classmates than to happy classmates. In contrast, conduct disorder patients’ interpersonal distance, did not differ between emotions. Interpersonal distance preferences were also associated with social anxiety and callous-unemotional traits.ConclusionThe findings suggest that conduct disorder patients fail to adjust their interpersonal behaviour to the facial expression of social interaction partners and that this is associated with social anxiety and callous-unemotional traits. A lack of adjustment to social cues might contribute to and maintain problems with peers in individuals with conduct disorder.

Social risk coding by amygdala activity and connectivity with dorsal anterior cingulate cortex.

Risk is a fundamental factor affecting individual and social economic decisions, but its neural correlates are largely unexplored in the social domain. The amygdala, together with the dorsal anterior cingulate cortex (dACC), is thought to play a central role in risk taking. Here, we investigated in human volunteers (n=20; 11 females) how risk (defined as variance of reward probability distributions) in a social situation affects decisions and concomitant neural activity as measured with fMRI. We found separate variance-risk signals for social and non-social outcomes in the amygdala. Specifically, amygdala activity increased parametrically with social reward variance of presented choice options and on separate trials with non-social reward variance. Behaviorally, 75% of participants were averse to social risk as estimated in a Becker-DeGroot-Marschak auction-like procedure. The stronger this aversion, the more negative was the coupling between risk-related amygdala regions and dACC. This negative relation was significant for social risk attitude but not for the attitude towards variance-risk in juice outcomes. Our results indicate that the amygdala and its coupling with dACC process objective and subjectively evaluated social risk. Moreover, while social risk can be captured with a framework originally established by finance theory for non-social risk, the amygdala appears to processes social risk largely separately from non-social risk.Significance statement Risk-the uncertainty of outcomes-has profound effects on decision-making and behavior. In social situations, uncertainty about others' behavior ('social risk') similarly guides our decisions and can contribute to social anxiety. Surprisingly little is known about the neural mechanisms processing social risk. Here we investigated neural activity when humans evaluated social risk derived from the uncertainty of personal compliments received from social partners. Activity in the amygdala, a brain structure implicated in emotion and social behavior, reflected social risk levels. Amygdala functional connectivity to the anterior cingulate cortex reflected individuals' aversion to social risk. Our findings extend risk evaluation into the social domain and pave the way for investigating social risk attitude in mental-health impairments, including social anxiety.

You say it‘s not me: the influence of offering external explanations of rejection and acceptance behavior on the perception of benevolence in borderline personality disorder

BackgroundInterpersonal impairments in patients diagnosed with borderline personality disorder (BPD) are characterized by the fear of being rejected and high levels of loneliness. Potential underlying factors are alterations in the processing of social interactions and the associated perceptions of social partners. In this regard, BPD patients tend to attribute the cause of negative rather than positive events to their own person and to perceive others as less trustworthy than healthy controls (HCs). To date, no study has investigated whether the effect of experimentally influenced causal attributions of social interactions on the perception of a social partner differs between BPD patients and HCs.MethodsA new virtual reality paradigm was developed to investigate the perception of benevolence following the induction of social rejection and acceptance, while experimentally manipulating whether an external cause for this behavior was provided. The data of 62 participants (32 HCs, 30 BPD patients) were analyzed using linear mixed-effects models. Associations of benevolence ratings with attributional style, rejection sensitivity, self-esteem, childhood trauma, and loneliness were investigated via correlational and multiple linear regression analyses.ResultsAcross both groups, a social partner was rated as less benevolent following rejection than following acceptance. An external explanation mitigated this negative effect of rejection. Overall, benevolence ratings were lower in BPD patients than in HCs. This group difference was stronger following acceptance than following rejection. Independent of acceptance and rejection, an external explanation was associated with a higher level of benevolence only in the HC group. No associations of the effects of the experimental conditions with attributional style, childhood trauma, rejection sensitivity, self-esteem, or loneliness were found.ConclusionOur findings indicate that acceptance and provided external explanations for rejection have a less positive impact on the perception of a social partner’s attitude toward oneself in BPD patients than in HCs. More research is needed to identify predictors of benevolence perception and which steps of social information processing are altered. The therapeutic implications include the importance of strengthening the perception and enjoyment of being accepted as well as improving the mentalizing ability of BPD patients.

Age of tobacco, nicotine and cannabis use initiation in Switzerland: a sequence analysis among adolescents and young adults.

To explore at what age youth start using tobacco and/or nicotine products, which product is used first, product initiation sequences, and whether some socio-demographic characteristics are associated with substance use initiation. Data were collected from an online questionnaire disseminated through social media and professional partners, targeting youth aged 14-25 in French-speaking Switzerland in August 2022. The final sample included 1362 participants. Respondents were asked whether they had already used cigarettes, e-cigarettes, hookah, snus, or cannabis at least once in their life (yes/no) and the age of the first time was asked for each substance when the answer was positive. Additionally, participants were asked about their substance use in the past 30 days. Respondents were classified according to age at onset of each tobacco/nicotine and cannabis product, and comparisons were made based on sociodemographic variables, including gender (cisgender female/cisgender male/transgender), perceived socioeconomic status (below average/average/above average), and age. Overall, in addition to those who reported no consumption, four distinct initiation profiles emerged from the classification. Cigarettes remain the most commonly used first product with an average age of 15.7 years. While cigarettes and hookah are present in all profiles, the order of first consumption varies from one profile to another, with cigarettes coming first in two profiles, hookah in one and e-cigarettes in the last. Furthermore, while the most common profile contains experimental consumption of the five products considered, some profiles do not contain cannabis, e-cigarettes and/or snus, for example. When divided by age groups, both 14-17-year-olds and 18-21-year-olds reported cigarette as their first product of initiation. Across the separate age groups (14-17, 18-21, 22-25), cigarettes consistently emerge as the primary used on average. Cigarettes remain the first product to be used, but the younger the respondents, the earlier they start using e-cigarettes, and very close to cigarettes. Regarding current consumption patterns, e-cigarettes are becoming increasingly prominent.

It is time to address fear of cancer recurrence in family caregivers: protocol for the feasibility and acceptability of a randomized pilot study of the online version of the Family Caregiver–Fear Of Recurrence Therapy (FC-FORT)

BackgroundFear of cancer recurrence (FCR) is common, persistent, and is associated with lower quality of life, impaired functioning, and psychological distress in cancer patients. Studies suggest that family caregivers of cancer patients experience equal or greater levels of FCR than patients themselves. In the past 5 years, several interventions have demonstrated their ability to reduce FCR among cancer patients and in patient-caregiver dyads. However, to date, no intervention exists to individually target family caregiver’s FCR. The aims of the proposed pilot study are to (1) assess the feasibility and acceptability of the newly adapted Family Caregiver–Fear Of Recurrence Therapy (FC-FORT) intervention to inform a larger randomized control trial study, and (2) estimate the clinical significance of FC-FORT. Initial evaluation of FC-FORT revealed high user satisfaction and usability.MethodsA parallel, two-group, pilot randomized controlled trial comparing FC-FORT to a waitlist control (care as usual) will be conducted. Participant inclusion criteria are (a) women family caregivers taking care of adult cancer patients (no recurrence), (b) experiencing clinical levels of FCR, (c) access to a computer/internet connection, and (d) living in Canada. Participants (n = 36) will be recruited at Ottawa and Toronto hospitals, previous study participant pools, through social media and community partners across Canada. Participants in the intervention group will complete the FC-FORT intervention (7 consecutive weeks of virtual group therapy and homework). Participants in the control group will be offered the intervention after their participation in the study. All participants will be asked to complete questionnaire packages at baseline (T0), immediately post-intervention (7 weeks; T1) and at 3-months post-intervention (T2). Feasibility (e.g., recruitment, allocation, fidelity), acceptability (e.g., dropout, completion, satisfaction) and clinical significance of secondary outcomes will be evaluated (i.e., FCR illness uncertainty). Participants in the intervention group will be asked to complete measures of group cohesion and therapeutic alliance and take part in a semi-structured exit interview exploring their overall experience with FC-FORT.DiscussionThis project will evaluate the acceptability and feasibility of the newly adapted FC-FORT to inform a larger trial.Trial registrationNCT, NCT05441384. Registered July 1st, 2022, https://classic.clinicaltrials.gov/ct2/show/NCT05441384

What Explains Differences in Minimum Wage Growth Between EU Member States?

Abstract There are considerable differences in minimum wage growth between EU member states with national minimum wages. Potential sources for these differences are discrepancies in economic fundamentals and institutional differences in how minimum wages are adjusted. Using a novel dataset based on macroeconomic data, institutional information on minimum wage setting and data on economic policy orientation and elections, the article tests whether growth differences in the minimum wage of 21 EU member states during the time period 2000 to 2020 can be explained by a catch-up dynamic in new EU member states, by different growth models of EU member states or by differences in the actors that are responsible for the adjustment of minimum wages. The results show that across the entire sample and irrespective of actors, minimum wage growth follows consumer price inflation and wage growth most closely. Higher than average minimum wage growth rates in EU member states stem from overshooting inflation during the period of EU accession, reducing wage inequality and increasing the Kaitz index. Actors also mattered for minimum wage growth. Adjustments by social partner consensus led to higher minimum wage growth than the benchmark of indexed minimum wages, introducing a distributive element to minimum wage adjustments.

Shared environments complicate the use of strain-resolved metagenomics to infer microbiome transmission.

In humans and other social animals, social partners have more similar microbiomes than expected by chance, suggesting that social contact transfers microorganisms. Yet, social microbiome transmission can be difficult to identify based on compositional data alone. To overcome this challenge, recent studies have used information about microbial strain sharing (i.e., the shared presence of highly similar microbial sequences) to infer transmission. However, the degree to which strain sharing is influenced by shared traits and environments among social partners, rather than transmission per se , is not well understood. Here, we first use a fecal microbiota transplant dataset to show that strain sharing can recapitulate true transmission networks under ideal settings when donor-recipient pairs are unambiguous and recipients are sampled shortly after transmission. In contrast, in gut metagenomes from a wild baboon population, we find that demographic and environmental factors can override signals of strain sharing among social partners. We conclude that strain-level analyses provide useful information about microbiome similarity, but other facets of study design, especially longitudinal sampling and careful consideration of host characteristics, are essential for inferring the underlying mechanisms.

Survivor Health Connection Project: Understanding Experiences of Accessing Health Care Among Those Affected by Intimate Partner Violence During the COVID-19 Pandemic.

Intimate partner violence (IPV) has short- and long-term health effects, including physical injuries and traumatic brain injury, as well as sexual, reproductive, and mental health issues. However, accessing necessary health care is often challenging for IPV survivors and became even more difficult during the COVID-19 pandemic. We examined access to health care among those affected by IPV during the COVID-19 pandemic to better connect survivors to health and social support services. The Health Resources and Services Administration's Office of Women's Health partnered with its Bureau of Primary Health Care, the Administration for Children and Families' Office of Family Violence Prevention and Services, and the National Domestic Violence Hotline (Hotline) on the 2-year Survivor Health Connection Project. The Hotline administered 2 surveys to its contacts: a 2-question postinteraction survey from March 29, 2021, through September 30, 2022, and a longer focused survey in 2021 and 2022 that measured barriers and restrictions to accessing health care, telehealth safety, and interactions with health care providers. Of 9918 respondents to the postinteraction survey, 6173 (62.2%) reported current health needs related to their abusive experience. Nearly half of 242 respondents to the 2021 survey (n = 106, 43.8%) indicated that the frequency or intensity of abuse increased during the COVID-19 pandemic, and 157 of 338 respondents to the 2022 survey (46.4%) reported that their partner had controlled and/or restricted their access to health care. Participants described barriers to accessing health care, including finances, health insurance coverage, and transportation. Findings illuminate opportunities to further support the health and social needs of those experiencing IPV, including continued coordination of efforts across health care and social service delivery partners.

And Baby Makes Three: Postpartum Changes in Male-Female Affiliative Interactions in White-Faced Capuchins.

In group-living primates, male investment in infants is highly variable. Previous research on polygynandrous primates found that male care of infants, whether direct or indirect, may be a means to increase offspring survival, increase social status, invest in future mating opportunities, and/or invest in future social or coalition partners, any of which may increase fitness outcomes. Relationships between male white-faced capuchins (Cebus imitator) and infants are highly variable, ranging from neutral to highly affiliative during periods of group stability to lethal during times of instability. We used genetic paternity analysis and behavioral observations to investigate the impact of paternity status, female dominance rank, male dominance rank, and infant sex on changes in rates of affiliation (contact and proximity) between capuchin males and females following the birth of an infant (n = 92 dyads). We used generalized linear mixed models and an information theory approach to select models for averaging. We found that overall rates of male-female affiliation increased following the birth of an infant (contact change: +1.09 ± 2.55%; proximity change: +1.16 ± 3.08%). Infant sex was the only significant explanatory variable; dyads that included males and females who gave birth to male infants experienced a significant increase in their time in contact and proximity in comparison to dyads with females who gave birth to female infants (contact change: p < 0.05 in 2/3 models; proximity change: p < 0.001 in 3/3 models). These findings add to previous data indicating that male capuchins do not recognize their offspring or have the motivation to preferentially invest in their care. We suggest that the observed sex bias may be a form of sex-specific socialization connected to the importance of forming long-term cooperative male bonds that are maintained via male parallel dispersal in this species.

Orangutans and chimpanzees produce morphologically varied laugh faces in response to the age and sex of their social partners

Laugh faces of humans play a key role in everyday social interactions as a pervasive tool of communication across contexts. Humans often vary the degree of mouth opening and teeth exposure when producing these facial expressions, which may depend on who their social partner is (e.g., their gender and age as well as their social relationship), serving this way different functions. Although it was found that laugh faces show evolutionary continuity across humans and non-human great apes according to the Principle of Maximum Parsimony, little is known about the function of laugh face variations from an evolutionary perspective. Hence, the present work examined the morphology of laugh faces in orangutan and chimpanzee dyadic play to test if they are modified with dependence on the playmate’s characteristics (sex, age and social relationship). In total, we analysed over 600 facial expressions of 14 orangutans and 17 chimpanzees by coding the specific muscle activations (Action Units, i.e. AUs) contributing to these expressions, using OrangFACS and ChimpFACS, respectively. Our results suggest that age difference and, to a lesser extent, playmate sex influence laugh face morphology in both taxa, but in opposite ways. While the orangutans of our study seem to expose their upper teeth (with AU10) and to pull the mouth corners (with AU12) more towards weaker partners (younger and female), possibly to communicate non-hostility, the chimpanzees showed both upper and lower teeth exposure (with AU10 and AU16) more often when interacting with the stronger partners (older individuals), possibly to communicate submissiveness. These findings suggest that the ability of humans to modify laugh faces with dependence on social partner characteristics has most likely evolved from pre-existing traits, going back at least to the last common ancestor of today’s great apes, including humans.

Burnout: a comprehensive review

Burnout has been the focus of extensive scientific research. The World Health Organization officially recognized burnout as an occupational phenomenon, defined as a syndrome resulting from chronic workplace stress that remains unmanaged and characterized by three dimensions: exhaustion, cynicism, and inefficacy. Existing literature highlights limitations in current measurement instruments for diagnostic purposes. These tools often yield scores that overlap with other conditions such as fatigue, anxiety, and depression. Chronic exposure to high job demands and low job resources emerges as the primary trigger for burnout. While individual characteristics (such as neuroticism) may increase susceptibility, specific personality traits associated with higher risk remain unclear. Burnout has adverse effects on both individuals and organizations. Typical interventions focus on stress relief and coping strategies to manage high job demands, but their effectiveness diminishes over time. Evidence from organizational interventions suggests that improving employees’ working conditions can reduce burnout risk. Combined interventions offer promise by creating a healthy work environment while empowering employees to handle occasional stress. Social partners should advocate for support in researching burnout, aiming for a clear diagnosis, effective treatment, and preventive measures to mitigate psychosocial risks in the workplace.Practical Relevance: The findings of this article highlight the importance of addressing both job demands and job resources to mitigate burnout in organizational settings. Implementing interventions that improve working conditions and provide adequate support can significantly reduce burnout risk and enhance employee well-being. Organizations should prioritize creating a healthy work environment and empowering employees with the necessary resources to manage workload effectively.

Ecology and Evolution of the Social Microbiome

Animals with close social relationships often have similar microbiomes. These socially structured microbiomes can arise through multiple mechanisms that are often difficult to disentangle, including transmission between social partners or via socially structured, shared environments. Here, we review evidence for socially structured microbiomes and propose methods to differentiate the mechanisms that give rise to them. We discuss the evolutionary implications of these mechanisms for both hosts and their microbiomes, including the possibility that social transmission selects for host-specialized microbiomes. We conclude by identifying outstanding questions related to social microbiomes and their implications for social evolution. We identify new or underutilized approaches like longitudinal study designs, strain-sharing analysis, and culture-based characterization to address these outstanding questions.

Policy utilisation of occupational safety and health research: results from a tripartite unicameral parliamentary system in Denmark

Background: Use of research evidence in policy decisions is under-researched. Especially, there is a need for more research in countries with different forms of government than bicameral legislatures. Aims and objectives: This article examines the impact of occupational safety and health (OSH) research on decision-makers in a tripartite unicameral parliamentary system (legislature and agreements). More specifically, we identify and discuss information acquisition and types of research use in policy decisions. Methods: Using both semi-structured and structured questions, we conducted 30 interviews distributed evenly within three groups of elite political actors: elected members of parliament; top-level public administrators; and social partner politicians. Analysis and reporting were subject to investigator triangulation. Findings: The three groups of elite political actors acquire information about OSH issues from different sources. The most important are: interest groups, networks and internal specialists. Findings show that elite actors generally use research knowledge conceptually and instrumentally, and to a lesser degree strategically and tactically. Many types of information influence politicians. They mostly perceive themselves as initiators of new research. The social partners primarily perceive themselves as users of new research results to initiate change and influence political decisions. Discussion and conclusion: How and when research knowledge is used differs between the three groups. It is important for researchers to tailor research communication to the particular needs of different stakeholders and interact directly with the elite actors and indirectly through lower level specialists from stakeholder organisations, and gain exposure through external sources such as the press and social media.

Self-efficacy and social support enable women to protect their pelvic floor health: A nonrandomized controlled trial in rural Nepal.

Carrying heavy loads increases the risk of pelvic organ disorders, particularly in low-income countries. Low self-efficacy hampers adoption of pelvic-floor-protective behaviors. The enabling hypothesis suggests that social support may strengthen women's behavioral self-efficacy. A three-arm parallel non-randomized controlled trial with 300 women and their social partners experimentally examined whether self-efficacy and social support can enable women's pelvic-floor-protective behaviors in rural Nepal. Three villages received (1) self-efficacy (2) self-efficacy and social support promotion, or (3) information only control. The co-primary outcomes were reduced weight carried and using protective lifting techniques at 2-month follow-up. Self-efficacy promotion increased the use of protective lifting techniques 9% more than information only (d = 0.28). Weight was reduced by 3 kg more when additionally promoting social support compared to self-efficacy alone (d = 0.39). Self-efficacy and social support promotion enable women to better protect their pelvic floor health and may complement educational approaches to health behavior change in low-resource populations.

The Impact of Social Media Use Among Millennial Couples

Social media use (SMU) among millennials (i.e., persons born between 1981 and 1996) is considered a hallmark behavior, with nearly 79% of individuals in this age bracket reportedly using social media multiple times a day. Despite the potential benefits of social media access, this communication method impedes forming deep connections, posing detrimental consequences to enduring romantic relationships among millennials. In recent years, SMU among millennials has skyrocketed, potentially contributing to the increased relational ruptures during this time, such as increased conflict and infidelity rates. With social media providing an outlet for individuals to text, share thoughts, photos, and intimate messages—all with the possibility of evading being caught, the millennial culture is shifting the dynamics of romantic relationships. As a result, therapists are seeing an increased number of couples from the millennial culture with heightened relational dysfunction due to social media and the digital world. Now more than ever, clinicians must be equipped with the necessary skills and competencies to assist millennial romantic relationships impacted by SMU. An in-depth literature review will provide a landscape to examine the role of social media, online dating, partner selection, and issues surrounding infidelity over the last decade. This article will conclude with a case study and recommendations for best practices to help facilitate healing among millennial relationships affected by negative SMU.

Population age structure shapes selection on social behaviour in a long-lived insect.

Social traits are expected to experience highly context-dependent selection, but we know little about the contextual factors that shape selection on social behaviours. We hypothesized that the fitness consequences of social interactions will depend on the age of social partners, and therefore that population age structure will shape evolutionary pressures on sociality. Here, we investigate the consequences of age variation at multiple levels of social organization for both individual fitness and sexual selection on social network traits. We experimentally manipulated the age composition of populations of the forked fungus beetle Bolitotherus cornutus, creating 12 replicate populations with either young or old age structures. We found that fitness is associated with variance in age at three different levels of organization: the individual, interacting social partners, and the population. Older individuals have higher reproductive success, males pay a fitness cost when they interact with old males and females achieve lower fitness in older populations. In addition to influencing fitness, population age structure also altered the selection acting on social network position in females. Female sociality is under positive selection only in old populations. Our results highlight age structure as an understudied demographic variable shaping the landscape of selection on social behaviour.This article is part of the discussion meeting issue 'Understanding age and society using natural populations'.

Social ageing can protect against infectious disease in a group-living primate.

The benefits of social living are well established, but sociality also comes with costs, including infectious disease risk. This cost-benefit ratio of sociality is expected to change across individuals' lifespans, which may drive changes in social behaviour with age. To explore this idea, we combine data from a group-living primate for which social ageing has been described with epidemiological models to show that having lower social connectedness when older can protect against the costs of a hypothetical, directly transmitted endemic pathogen. Assuming no age differences in epidemiological characteristics (susceptibility to, severity and duration of infection), older individuals suffered lower infection costs, which was explained largely because they were less connected in their social networks than younger individuals. This benefit of 'social ageing' depended on epidemiological characteristics and was greatest when infection severity increased with age. When infection duration increased with age, social ageing was beneficial only when pathogen transmissibility was low. Older individuals benefited most from having a lower frequency of interactions (strength) and network embeddedness (closeness) and benefited less from having fewer social partners (degree). Our study provides a first examination of the epidemiology of social ageing, demonstrating the potential for pathogens to influence the evolutionary dynamics of social ageing in natural populations.This article is part of the discussion meeting issue 'Understanding age and society using natural populations'.