Leaders-cheaters in male group cooperation: differences in nonverbal communication and genetic factors

Here we report on the results of an experimental study investigating "who?" emerges as a leader in the context of male group cooperation and "how?" they do that. The study was designed based on the iterated Public Goods Game, played face-to-face in groups composed of four male strangers. The game involved interactions both with and without communication to allow the assessment of individual cooperative strategies, leadership potential, and individual features of positive nonverbal expressiveness during interactions. Along with the individual behavioural characteristics we have addressed personality traits (the Big Five) and an oxytocin receptor gene polymorphism (OXTR: SNP rs53576; A/G) as putative markers of individual sociability. Our results revealed that emergent leaders most often employed the strategy of unconditional cooperation ("altruism") and were characterized by enhanced positive facial expressiveness and extraversion compared to non-leaders. However, a fraction of emergent leaders (25%) turned out to be occasional free-riders ("cheaters"). Their distinctive features were the highest scores on extraversion, exaggerated activity in negotiations, and over-expression of positive nonverbal elements. Given the high efficiency of leaders-cheaters' behaviour, we consider this result as the evidence for supernormal stimuli functioning in humans. Moreover, leaders-cheaters were characterized by a specific allelic frequency of OXTR rs53576 (heterozygosity: AG). The homozygous GG variant of this SNP is argued to be associated with prosociality, and the AA, on the contrary, with poor sociability. The heterozygous variant (AG) probably is a compromise that enables its carriers to successfully combine high social skills with anti-social behavior (free-riding). This finding supports existing evidence on the role of OXTR rs53576 in human social behaviour

Maasai Identify Male Altruists by Facial Appearance

In this experimental study, we continue investigating an association between facial morphology and individual psychological characteristics. The study was conducted in the population of Maasai (Ngorongoro, Tanzania) in two stages during field trips in 2016 and 2021. At the first stage, we collected anthropological photo portraits from 305 individuals (123 women and 182 men) and interviewed them to identify the propensity to help others. Six generalized morphed portraits of Maasai (men and women) were created based on individual propensity to help. At the second stage of the study, portraits were presented to 200 Maasai, men and women from the same population. The portraits were evaluated according to the degree of expression of four qualities: physical strength, proneness to help others, a "good friend", and self-confidence. The results of the study revealed that representatives of the same population are able to distinguish altruistic men by their facial shape. Men who were prone to provide assistance to others were perceived as physically stronger. No such association was found for female portraits. The results are interpreted from the standpoint of evolutionary psychology.</p

Individual variation in body odor

Humans produce numerous volatile compounds from different areas of the body, either as a direct result of metabolic processes or indirectly via metabolismof resident microflora. Body odors vary between individuals, partly due to genetic differences, but odors of the same individual also vary across time due to environmental influences. We discuss how at least part of the genetic influence appears to be related to certain personality characteristics and to sexual orientation. We then review the current state of the art in terms of intraindividual variation, including effects of intrinsic factors, such as hormonal influences on body odor and environmental factors, namely effects of diet and certain diseases. Some of these changes can be perceived by other individuals and might therefore provide social cues of current motivational, nutritional, and health status. Finally, we discuss how specific odor profiles associated with certain infectious diseases and metabolic disorders can be used as a cheap and efficient medical screening tool