Olfactory cues of naturally occurring systemic inflammation: A pilot study of seasonal allergy

Introduction: In an attempt to avoid contact with infectious individuals, humans likely respond to generalised rather than specific markers of disease. Humans may thus perceive a non-infectious individual as socially less attractive if they look (e.g., have facial discoloration), move (e.g., have a slower walking pace), or sound (e.g., sneeze) sick. This pilot study tested whether humans are averse to the body odour of non-infectious individuals with a low-grade systemic inflammation. Methods: We collected the axillary body odour of individuals with severe seasonal allergy (N = 14) and healthy controls (N = 10) during and outside the allergy season and measured serum levels of two inflammatory cytokines (tumor necrosis factor-α, interleukin-5). Independent participants (N = 67) then sampled and rated these odours on intensity and pleasantness. Results: While individuals with seasonal allergy had nominally more unpleasant and intense body odours during the allergy season - relative to outside of the allergy season and to healthy controls - these effects were not significant. When examining immune markers, the change in perceived pleasantness of an individual’s body odour (from out- to inside pollen season), was significantly related to the change in their interleukin-5 levels but not to tumor necrosis factor-α. Discussion: Our findings tentatively suggest that the human olfactory system could be sensitive to inflammation as present in a non-communicable condition. Larger replications are required to determine the role of olfaction in the perception of infectious and non-infectious (e.g., chronic diseases) conditions.publishedVersio

Sexual selection and the evolution of cooperative behaviour in humans and the mound-building mouse

Au cours des 150 dernières années, l'évolution de la coopération n'a cessé d'intriguer les biologistes de l'évolution. Les comportements coopératifs, qui procurent un avantage direct au bénéficiaire, ne peuvent être sélectionnés que si, pour le coopérateur, les bénéfices directs et/ou indirects dépassent le coût. De nombreuses observations chez l'Homme et chez d'autres espèces animales suggèrent que les comportements coopératifs pourraient être maintenus par la sélection sexuelle. Pourtant, ce champ de recherche est quasiment inexploré, que ce soit chez l'Homme ou chez les autres espèces sociales. Afin d'examiner le rôle potentiel de la sélection sexuelle sur les comportements coopératifs, deux modèles biologiques ont été utilisés : l'Homme et la Souris glaneuse (Mus spicilegus). Chez l'Homme, la propension à coopérer a été quantifiée dans deux populations humaines (française et sénégalaise) principalement par des méthodes empruntées à l'économie expérimentale (jeu du bien public). Chez la souris glaneuse, l'investissement individuel dans la construction collective d'un tumulus pour l'hivernage a été mesuré en captivité. Les résultats soutiennent partiellement nos prédictions, à savoir : (i) que les individus coopèrent davantage en présence de partenaires sexuels potentiels, (ii) que les coopérateurs sont préférés comme partenaires sexuels, et que (iii) ces préférences conduisent à un appariement selon la coopérativité. De plus, ils suggèrent que des traits physiques (visuels, olfactifs, ou acoustiques) puissent être utilisés pour détecter la coopérativité d'un individu. Chez l'Homme, en particulier, des traits statiques du visage, dont au moins certains sont lisibles inter-culturellement, semblent impliqués. Enfin, une éventuelle association entre les comportements coopératifs et une hormone sexuelle, la testostérone, a été examinée. Pris dans leur ensemble, nos résultats suggèrent que la sélection sexuelle pourrait être impliquée dans l'évolution et le maintien de la coopération et ouvrent donc la voie à de nouvelles recherches, examinant son influence dans diverses populations humaines, ainsi que dans de nombreuses autres espèces sociales. Mots clés : Coopération, Altruisme, Générosité, Investissement parental, Attractivité, Jeu du bien public, Choix de partenaire, Homogamie, signal de coopérativité et détection, Régulation hormonale, Testostérone.Over the past 150 years, the evolution of cooperation has challenged evolutionary biologists. Cooperative behaviour provide a benefit to the recipient and can only be selected for if it also provides direct and/or indirect benefits to the actor that accepted the costs of the cooperative action. Many observations in humans and other animal species suggest that cooperative behaviour could be maintained by sexual selection. However, the hypothesis that sexual selection could be involved in the evolution of cooperation has not received much attention in the recent literature. In order to examine the potential role of sexual selection in cooperative behaviour, two biological models were used: humans and the Mound-building mouse (Mus spicilegus). In two human populations (French and Senegalese populations), cooperativeness was quantitatively measured, mainly by an economic game (the public good game). The spontaneous cooperativeness exhibited during collective mound-building for overwintering was assessed in captivity for Mus spicilegus. The results partly support our predictions: (i) individuals cooperativeness increase in the presence of potential sexual partners, (ii) cooperators are preferred as sexual partners, (iii) these preferences lead to assortative mating based on cooperativeness. Moreover, they suggest that physical traits (visual, olfactory, or acoustic) could be used to detect individual cooperativeness. In humans, static facial traits seem to be involved, and some of them appear to be inter-culturally readable. Finally, a potential association between cooperative behaviour and testosterone levels, a sex hormone, was examined. Together, these results suggest that sexual selection could be involved in the evolution and the maintenance of cooperation. Furthers studies are needed, in different human populations and in different social species, to further investigate the role of sexual selection in cooperative behaviour. Keywords: Cooperation, Altruism, Generosity, Parental investment, Attractiveness, Public Good Game, Mate choice, Homogamy, Detection, Signaling, Hormonal regulation, Testosterone

Does the presence of a physically disabled person in the group increase cooperation? An experimental test of the empathyaltruism hypothesis: Cooperation between individuals with and without disabilities

The empathy-altruism hypothesis postulates that the awareness of others’ need, pain, or distress increases empathetic feelings, which in turn triggers cooperative behaviour. Although some evidence supports this hypothesis, previous studies were prone to the ‘experimenter demand effects’ raising concerns about the interpretation of the results. To avoid this issue, we designed a laboratory experiment where we examined whether the presence of individuals with a genuine physical disability would increase group cooperation in a public goods game. By manipulating the group composition during a social dilemma, we created a more ecologically valid environment closer to real-life interactions. Our results showed that the presence of physically disabled individuals did not affect group cooperation. Specifically, their presence did not affect the contributions of their physically abled partners. The lack of a surge in cooperative behaviour questions the interpretation of previous studies and suggests that they may be explained by an experimenter demand effect. Alternatively, our results may also suggest that in the context of a social dilemma with real stakes, people with physical disabilities are not perceived as being in need or do not induce enough empathy to overweight the cost of cooperation and trigger cooperative behaviours

Mieux comprendre le don de sang. La piste des mécanismes biologiques et cognitifs. Enjeux et défis

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Female mound-building mice prefer males that invest more in building behavior, even when this behavior is not observed

International audienceFemale mound-building mice prefer males that invest more in building behavior, even when this 1 behavior is not observed 2 Abstract 9 Through behavioral correlations, mate choice could influence the evolution of traits that are not 10 directly selected for, or even observed. We addressed whether mound building, a unique collective 11 behavior observed in Mus spicilegus, could be favored by female mate choice, irrespective of whether 12 females were able to observe the behavior. First, we introduced mixed sex groups of wild-born mice in 13 large terraria with building materials, and assessed male variation in building investment. Second, we 14 presented females with a choice between males that invested the most versus the least in building. 15 Females were either able to observe the males during building or not. Third, because overwintering 16 juveniles rely on mound protection, we hypothesized that building could be a form of paternal care, 17 and assessed whether males that invested more in building also invested more in direct offspring care. 18 We showed that females were more attracted to males that invested the most in building, even when 19 these behaviors were not observed. In addition, direct offspring care was negatively correlated with 20 males' investment in building, suggesting that two alternative paternal care strategies (mound building 21 versus direct offspring care) may exist. Our study supports the hypothesis that building could be 22 detectable by phenotypic cues that differ from building behavior per se and that mate choice may 23 influence the evolution and maintenance of mound building that several authors describe as a common 24 good. 25 2

Men increase contributions to a public good when under sexual competition

International audienceWhy humans cooperate in large groups and with non-kin remains a puzzle for researchers across the natural and social sciences. Investigating whether cooperation is sexually selected could contribute to an understanding of the evolution of human cooperation. Competition for access to mates could indeed select for cooperation. Using controlled laboratory experiments, we analyse whether and how the sex composition of a social environment, testosterone level, and relationship status affect contributions to a public good. The results show that variation in sex composition alters the amount of money that single men (but not men in a couple or women) contribute to a public good. Notably, in line with the competitive helping hypothesis, awareness of the presence of a woman leads to larger contributions by single men, most likely by triggering their competitiveness to be the most cooperative man in the group. However, we find no link between basal testosterone level and cooperativeness. We argue that men, notably single men, adopt cooperative behaviours as a signalling strategy in the context of mate choice and hence that cooperation is partly sexually selected. Our findings highlight the need to consider sexual selection as an additional mechanism for cooperation. The evolution of cooperation between unrelated individuals remains a challenging issue for evolutionary biologists 1. The puzzle is that cooperative behaviour is beneficial to recipients but is costly to the actor. Theory suggests that cooperative acts can only be selected if the costs of cooperation are compensated by fitness benefits 2. Some theoretical 3–5 and experimental studies 6,7 have shown that sexual benefits could maintain cooperation in a group. Investigations into whether cooperation is sexually selected could thus contribute to our understanding of the evolution of cooperation. Based on controlled and incentivized laboratory experiments, we show that variation in the sex composition of a group of four individuals alters the amount of money that single men (but not men in a couple or women) contribute to a public good, when the sex composition is common knowledge. Notably, in line with the competitive helping hypothesis, awareness of the presence of a woman in the group likely increases single men's competitiveness in their willingness to appear as the most cooperative individual, leading to larger contributions by those men. We also investigate the potential influence of basal testosterone as a proximate mechanism of this behaviour. However, no association between male testosterone level and contribution to a public good is detected. Despite the absence of testosterone influence on cooperation, we argue that men, especially single men, adopt cooperative behaviours as a signalling strategy in the context of mate choice, and hence that cooperation is – at least partly-sexually selected in humans. Observations in non-human animal species suggest that sexual selection could be implicated in the evolution of cooperation. Male Lance-tailed Manakins (Chiroxiphia lanceolata) perform cooperative efforts, such as singing duets and dancing with other males, which increases their chances of mating with females 8. In chimpanzees (Pan troglodytes), males exchange political support from the dominant male for mating opportunities 9 : dominant males, in turn, tolerate males who support them most frequently in conflicts, with the result that supporters copulate more often than other males. In humans, there is also evidence that cooperative behaviour toward non-kin could be sexually selected. For example, several studies suggest that cooperative traits are implicated in mate choice 10–12 and that women are more sensitive to those traits in sexual partners than men are 10

Does he sound cooperative? Acoustic correlates of cooperativeness

The sound of the voice has several acoustic features that influence the perception of how cooperative the speaker is. It remains unknown, however, whether these acoustic features are associated with actual cooperative behaviour. This issue is crucial to disentangle whether inferences of traits from voices are based on stereotypes, or facilitate the detection of cooperative partners. The latter is likely due to the pleiotropic effect that testosterone has on both cooperative behaviours and acoustic features. In the present study, we quantified the cooperativeness of native French‐speaking men in a one‐shot public good game. We also measured mean fundamental frequency, pitch variations, roughness, and breathiness from spontaneous speech recordings of the same men and collected saliva samples to measure their testosterone levels. Our results showed that men with lower‐pitched voices and greater pitch variations were more cooperative. However, testosterone did not influence cooperative behaviours or acoustic features. Our finding provides the first evidence of the acoustic correlates of cooperative behaviour. When considered in combination with the literature on the detection of cooperativeness from faces, the results imply that assessment of cooperative behaviour would be improved by simultaneous consideration of visual and auditory cues

Assessing sickness behavior in the French: Validation of the French translation of the sickness questionnaire (SicknessQ) in a non-clinical French population

The Sickness Questionnaire (SicknessQ) is a questionnaire developed to assess symptoms of sickness behavior, including somatic, behavioral, and affective dimensions. To promote cross-cultural assessments of sickness behavior, we aim to expand the use of this questionnaire to other populations and languages. The aim of the present study was to evaluate the French translation of SicknessQ in a French-speaking general population during the COVID-19 pandemic. One hundred and thirty-nine individuals completed the SicknessQ online, along with the construct criteria measures of self-rated health, state anxiety (STAI-S), and depressive symptoms (PHQ-9). The principal component analyses revealed two components: the first component included seven items concerning mood, motivation and experiences of fatigue and pain; the second component included three items concerning somatic sickness symptoms. Higher scores on the total scale and the two component subscales were associated with poorer self-rated health and higher STAI-S and PHQ-9 scores. Since the associations with construct criteria variables were relatively similar between the single- and the two-dimensional solutions, both the total scale and the subscales of the two components of the French SicknessQ can be used in future studies to measure sickness behavior in French-speaking populations

Speech Acoustic Features: A Comparison of Gay Men, Heterosexual Men, and Heterosexual Women

International audiencePotential differences between homosexual and heterosexual men have been studied on a diverse set of social and biological traits. Regarding acoustic features of speech, researchers have hypothesized a feminization of such characteristics in homosexual men, but previous investigations have so far produced mixed results. Moreover, most studies have been conducted with English-speaking populations, which calls for further cross-linguistic examinations. Lastly, no studies investigated so far the potential role of testosterone in the association between sexual orientation and speech acoustic features. To fill these gaps, we explored potential differences in acoustic features of speech between homosexual and heterosexual native French men and investigated whether the former showed a trend toward feminization by comparing theirs to that of heterosexual native French women. Lastly, we examined whether testosterone levels mediated the association between speech acoustic features and sexual orientation. We studied four sexually dimorphic acoustic features relevant for the qualification of feminine versus masculine voices: the fundamental frequency, its modulation, and two understudied acoustic features of speech, the harmonics-to-noise ratio (a proxy of vocal breathiness) and the jitter (a proxy of vocal roughness). Results showed that homosexual men displayed significantly higher pitch modulation patterns and less breathy voices compared to heterosexual men, with values shifted toward those of heterosexual women. Lastly, testosterone levels did not influence any of the investigated acoustic features. Combined with the literature conducted in other languages, our findings bring new support for the feminization hypothesis and suggest that the feminization of some acoustic features could be shared across languages