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

Methodological issues when using face prototypes: A case study on the Faceaurus dataset

Prototype faces, created by averaging faces from several individuals sharing a common characteristic (for example a certain personality trait), can be used for highly informative experimental designs in face research. Although the facial prototype method is both ingenious and useful, we argue that its implementation is associated with three major issues: lack of external validity and non-independence of the units of information, both aggravated by a lack of transparency regarding the methods used and their limitations. Here, we describe these limitations and illustrate our claims with a systematic review of studies creating facial stimuli using the prototypes dataset “Faceaurus” (Holtzman, 2011). We then propose some solutions that can eliminate or reduce these problems. We provide recommendations for future research employing this method on how to produce more generalisable and replicable results

Methodological issues when using face prototypes: A case study on the Faceaurus dataset

Prototype faces, created by averaging faces from several individuals sharing a common characteristic (for example a certain personality trait), can be used for highly informative experimental designs in face research. Although the facial prototype method is both ingenious and useful, we argue that its implementation is associated with three major issues: lack of external validity and non-independence of the units of information, both aggravated by a lack of transparency regarding the methods used and their limitations. Here, we describe these limitations and illustrate our claims with a systematic review of studies creating facial stimuli using the prototypes dataset “Faceaurus” (Holtzman, 2011). We then propose some solutions that can eliminate or reduce these problems. We provide recommendations for future research employing this method on how to produce more generalisable and replicable results

Is cooperativeness readable in static facial features? An inter-cultural approach

International audienceThere is evidence in the literature that non-verbal physical features are used as cues for a propensity to cooperate. However, further studies of the human ability to visually detect cooperativeness are required. In particular, the existence of static facial cues of altruism remains questionable. Moreover, an investigation of both sex differences and cross-cultural applicability with respect to altruism detection skills is crucial in the context of the evolution of human cooperation. In this study, we used both a public good game and a charitable contribution to assess the cooperativeness of 156 men and 172 women in rural Senegal and took facial photographs of these individuals. The second portion of the study was conducted in France. In total, 194 men and 171 women were asked to distinguish the most and least selfish individual from a series of 80 pairs of Senegalese facial photographs, each pair consisting of the highest and the lowest contributor from a group in the public good game. Using mixed modeling techniques, we controlled for facial masculinity, age and socio-economic status. For male pairs, both male and female French raters were able to identify more often than by chance which individual made the smallest contribution to the public good in each group; however, detection was not successful with female faces. These results suggest that sex-specific traits are involved and that only male facial traits indicating cooperative skills are, at least inter-culturally, readable. The specific facial traits involved are investigated. However, the charitable contribution was not correlated with the contribution to the public good, and further work is necessary to identify which specific altruistic traits are detectable and to assess the generality of these results

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