Both face and body images were rated as being more attractive when presented in groups than when presented in isolation, demonstrating that the cheerleader effect is not restricted to faces

The ‘cheerleader effect’ in facial and bodily attractiveness: A result of memory bias and not perceptual encoding. Jean Y J Hsieh et al. Quarterly Journal of Experimental Psychology, November 11, 2020. https://doi.org/10.1177/1747021820976087

Rolf Degen's take: https://twitter.com/DegenRolf/status/1326778715255304192

Abstract: Individual faces are rated as more attractive when presented in a group compared to when presented individually; a finding dubbed the ‘cheerleader effect’. As a relatively recent discovery, the conditions necessary to observe the effect are not clearly understood. We sought to better define these conditions by examining two parameters associated with the effect. Our first aim was to determine whether the effect is specific to faces or occurs also for human bodies. Both face and body images were rated as being more attractive when presented in groups than when presented in isolation, demonstrating that the cheerleader effect is not restricted to faces. Further, the effect was significantly larger for bodies than faces. Our second aim was to determine whether the cheerleader effect originates from a bias in memory or occurs during perceptual encoding. Participants in the ‘memory’ condition provided attractiveness ratings after images had been removed from the testing screen, whereas participants in the ‘perceptual’ condition provided ratings while the images remained visible, thereby eliminating the memory components of the paradigm. Significant cheerleader effects were only observed in the memory condition. We conclude that the cheerleader effect for faces and bodies is due to a bias in memory and does not occur at an initial stage of perceptual encoding.

Keywords: body perception, cheerleader effect, memory bias, attractiveness, perceptual encoding

Not only is there a smell of fear, but this also renders fear “contagious”: People who smelled armpit fear became physiologically aroused (increased galvanic skin response)

A Path to Identifying the Smell of Fear. Shiri Karagach et al. Chemical Senses, 2020, Vol 45, 699–804, The Eighteenth International Symposium on Olfaction and Taste (ISOT XVIII) and the Fifty-First Association for Chemoreception Sciences Annual Meeting (AChemS LI), Aug 2020, doi:10.1093/chemse/bjaa061

Rolf Degen's take: https://twitter.com/DegenRolf/status/1326592651186085889

Abstract: Several studies found that body odor collected from human participants in a state of fear has pronounced behavioral and physiological effects on conspecifics. Body-odor can arise from sweat emitted primarily from two types of glands: eccrine and apocrine. The relative contribution of these sources to human social chemosignaling remains unclear. The importance of understanding this is not only the basic building blocks of social chemosignaling behavior, but it is a critical methodological step towards the holy grail of social chemosignaling research, namely identifying the molecules at play. To identify social chemosignals, from where should we collect emissions? From eccrine or apocrine regions? To address these questions, we collected eccrine (lower back)and apocrine (armpit) sweat from ~750 individuals in two states: Fear - first-time military parachuting, and Control - physical exercise. We then exposed ~25 experimental participants to these sources. We found that relative to control, fear sweat was perceived as more intense, less pleasant and rated as more fearful. Measurement of the galvanic skin response (GSR), a robust measure of autonomic arousal, implied pronounced GSR responses to armpit but not lower-back fearsweat. In other words, not only is there a smell of fear, but this also renders fear “contagious”: People who smelled armpit fear became physiologically aroused. Given that armpit sweat is a potential meaningful source for chemosignaling, further chemical analysis was facilitated with gas-chromatography mass-spectrometry (GC-MS). Principal-component analysis (PCA) uncovered clear separation between armpit fear and control sweat. This allowed us to identify a limited bouquet of chemicals evident in fear but not control sweat.

Paternity uncertainty profoundly shapes human relationships, reducing not only the investment contributed by paternal versus maternal kin, but also forms of prosocial behavior between individuals

Bressan, Paola, and Peter Kramer. 2020. “Human Kin Detection.” PsyArXiv. November 11. doi:10.1002/wcs.1347

Rolf Degen's take: https://twitter.com/DegenRolf/status/1326494109268373504

Abstract: Natural selection has favored the evolution of behaviors that benefit not only one's genes, but also their copies in genetically related individuals. These behaviors include optimal outbreeding (choosing a mate that is neither too closely related, nor too distant), nepotism (helping kin), and spite (hurting non-kin at a personal cost), and all require some form of kin detection or kin recognition. Yet, kinship cannot be assessed directly; human kin detection relies on heuristic cues that take into account individuals' context (whether they were reared by our mother, or grew up in our home, or were given birth by our spouse), appearance (whether they smell or look like us), and ability to arouse certain feelings (whether we feel emotionally close to them). The uncertainties of kin detection, along with its dependence on social information, create ample opportunities for the evolution of deception and self-deception. For example, babies carry no unequivocal stamp of their biological father, but across cultures they are passionately claimed to resemble their mother's spouse; to the same effect, 'neutral' observers are greatly influenced by belief in relatedness when judging resemblance between strangers. Still, paternity uncertainty profoundly shapes human relationships, reducing not only the investment contributed by paternal versus maternal kin, but also prosocial behavior between individuals who are related through one or more males rather than females alone. Because of its relevance to racial discrimination and political preferences, the evolutionary pressure to prefer kin to non-kin has a manifold influence on society at large.