How to create shared symbols

Human cognition and behavior are dominated by symbol use. This paper examines the social learning strategies that give rise to symbolic communication. Experiment 1 contrasts an individual-level account, based on observational learning and cognitive bias, with an inter-individual account, based on social coordinative learning. Participants played a referential communication game in which they tried to communicate a range of recurring meanings to a partner by drawing, but without using their conventional language. Individual-level learning, via observation and cognitive bias, was sufficient to produce signs that became increasingly effective, efficient, and shared over games. However, breaking a referential precedent eliminated these benefits. The most effective, most efficient, and most shared signs arose when participants could directly interact with their partner, indicating that social coordinative learning is important to the creation of shared symbols. Experiment 2 investigated the contribution of two distinct aspects of social interaction: behavior alignment and concurrent partner feedback. Each played a complementary role in the creation of shared symbols: Behavior alignment primarily drove communication effectiveness, and partner feedback primarily drove the efficiency of the evolved signs. In conclusion, inter-individual social coordinative learning is important to the evolution of effective, efficient, and shared symbols

Reply to Martens: Various factors may enable large populations to enhance cumulative cultural evolution, but more evidence is needed

Martens (1) suggests that including model-based bias (e.g., prestige) in our experiment would have enhanced cumulative cultural evolution (CCE) in the larger populations reported in our paper (2). This is a plausible hypothesis, but not one our experiment was designed to test. Given the controversy around the relationship between population size and CCE (3), our experiment was designed to isolate the basic effect of population size on CCE by excluding extraneous factors, including model-based bias. In our experiment increasing population size did not enhance CCE. We do not conclude that larger populations do not enhance CCE but that other factors may be necessary to see this benefit.Output Type: Lette

Increasing population size can inhibit cumulative cultural evolution

The extent to which larger populations enhance cumulative cultural evolution (CCE) is contentious. We report a large-scale experiment (n = 543) that investigates the CCE of technology (paper planes and their flight distances) using a transmission-chain design. Population size was manipulated such that participants could learn from the paper planes constructed by one, two, or four models from the prior generation. These social-learning conditions were compared with an asocial individual-learning condition in which individual participants made repeated attempts at constructing a paper plane, without having access to any planes produced by other participants. Larger populations generated greater variation in plane performance and gave participants access to better-adapted planes, but this did not enhance CCE. In fact, there was an inverse relationship between population size and CCE: plane flight distance did not improve over the experimental generations in the 2-Model and 4-Model conditions, but did improve over generations in the 1-Model social-learning condition. The incremental improvement in plane flight distance in the 1-Model social-learning condition was comparable to that in the Individual Learning condition, highlighting the importance of trial-and-error learning to artifact innovation and adaptation. An exploratory analysis indicated that the greater variation participants had access to in the larger populations may have overwhelmed their working memory and weakened their ability to selectively copy the best-adapted plane(s). We conclude that larger populations do not enhance artifact performance via CCE, and that it may be only under certain specific conditions that larger population sizes enhance CCE

Preference for male risk takers varies with relationship context and health status but not COVID risk

Risk taking is more commonly shown by males than females and has a signalling function, serving to advertise one’s intrinsic quality to prospective mates. Previous research has established that male risk takers are judged as more attractive for short-term flings than long-term relationships, but the environmental and socioeconomic context surrounding female preferences for male risk takers has been overlooked. Using a survey instrument, we examined female preferences for male risk takers across 1304 females from 47 countries. We found preferences for physical risk takers to be more pronounced in females with a bisexual orientation and females who scored high on risk proneness. Self-reported health was positively associated with preferences for high risk takers as short-term mates, but the effect was moderated by country-level health, i.e. the association was stronger in countries with poorer health. The security provided by better health and access to health care may allow females to capitalise on the genetic quality afforded by selecting a risk-prone male whilst concurrently buffering the potential costs associated with the risk taker’s lower paternal investment. The risk of contracting COVID-19 did not predict avoidance of risk takers, perhaps because this environmental cue is too novel to have moulded our behavioural preferences

Resistance to Oxidative Stress Is Associated with Metastasis in Mucocutaneous Leishmaniasis

Mucocutaneous leishmaniasis (MCL) in South and Central America is characterized by the dissemination (metastasis) of Leishmania Viannia subgenus parasites from a cutaneous lesion to nasopharyngeal tissues. Little is known about the pathogenesis of MCL, especially with regard to the virulence of the parasites and the process of metastatic dissemination. We previously examined the functional relationship between cytoplasmic peroxiredoxin and metastatic phenotype using highly, infrequently, and nonmetastatic clones isolated from an L. (V.) guyanensis strain previously shown to be highly metastatic in golden hamsters. Distinct forms of cytoplasmic peroxiredoxin were identified and found to be associated with the metastatic phenotype. We report here that peroxidase activity in the presence of hydrogen peroxide and infectivity differs between metastatic and nonmetastatic L. (V.) guyanensis clones. After hydrogen peroxide treatment or heat shock, peroxiredoxin was detected preferentially as dimers in metastatic L. (V.) guyanensis clones and in L. (V.) panamensis strains from patients with MCL, compared with nonmetastatic parasites. These data provide evidence that resistance to the first microbicidal response of the host cell by Leishmania promastigotes is linked to peroxiredoxin conformation and may be relevant to intracellular survival and persistence, which are prerequisites for the development of metastatic diseas