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

Équipe expérimentale : Étude des processus infectieux en confinement A1à A3 sur les animaux de rente, de laboratoire, de loisir et de la faune sauvage

Présentation du poster en 180 sec de l'activité des équipes expérimentation / élevage de la PFIENational audienc

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

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

Are non-verbal facial cues of altruism cross-culturally readable?

International audienceAlthough both dynamic (i.e., facial expressions) and static facial traits are used as cues of altruism, only static facial traits have been shown to be cross-culturally readable with respect to altruism detection skills. To investigate whether dynamic facial cues of altruism are also cross-cultural, we asked French subjects to estimate the altruism of Japanese individuals on the basis of silent video clips. These video clips were taken from a previous experiment, which found that Japanese raters were able to accurately estimate the altruism of a videotaped Japanese individual. By using the same design and stimuli in France, we found that French raters were unable to assess the altruism of a Japanese individual. Hence, our results suggest that dynamic facial cues of altruistic intent are culturally specific rather than universally readable

Sexual Selection of Human Cooperative Behaviour: An Experimental Study in Rural Senegal

<div><p>Human cooperation in large groups and between non-kin individuals remains a Darwinian puzzle. Investigations into whether and how sexual selection is involved in the evolution of cooperation represent a new and important research direction. Here, 69 groups of four men or four women recruited from a rural population in Senegal played a sequential public-good game in the presence of out-group observers, either of the same sex or of the opposite sex. At the end of the game, participants could donate part of their gain to the village school in the presence of the same observers. Both contributions to the public good and donations to the school, which reflect different components of cooperativeness, were influenced by the sex of the observers. The results suggest that in this non-Western population, sexual selection acts mainly on men’s cooperative behaviour with non-kin, whereas women’s cooperativeness is mainly influenced by nonsexual social selection.</p> </div

The influence of the categories of observers on generosity towards school children.

<p>Generosity was measured as the probability of donating among (a) male and (b) female participants, and as the amount donated by (c) male and (d) female participants who made a non-zero donation (raw data). Logistic regression models showed that men’s propensity to make a donation in the presence of young female observers was significantly higher than in the presence of male observers, but not significantly different from their probability of making a donation in the presence of old female observers. For the female participants, logistic regression models showed that they were more likely to donate in the presence of female observers than in the presence of male observers. Among the participants who made a non-zero donation, linear mixed models showed that men were more generous in the presence of young female observers than in the presence of old female observers, but not significantly more than in the presence of male observers. No significant difference was found in the amounts donated by women.</p

Caractérisation de laits de juments comtoises. Aptitude à la coagulation enzymatique et à la filtration membranaire . Fabrications de produits fromagers

Comtoise mare milk produced in three different breeds from Franche-Comté were assessed for their physico-chemical, biochemical and microbiological content along the lactation 2008. Exploratory trials were conducted also to determine the behaviour of the milk when submitted to fitlration, enzymatic coagulation and cheese manufacture. Le lait de jument Comtoise produit dans 3 élevages de Franche-Comté a fait l'objet d'une caractérisation physico-chimique, biochimique et microbiologique au cours de la saison de production 2008. Des essais technologiques exploratoires incluant l'aptitude à la filtration membranaire et à la coagulation enzymatique, ainsi que la fabrication de fromages selon 2 types de technologie ont été réalisés