Cultural diffusion dynamics depend on behavioural production rules

Culture is an outcome of the acquisition of knowledge about behaviour through social transmission, and its subsequent production. Transmission and production are often discussed interchangeably or modeled separately, yet to date, no study has accounted for both processes and explored their interaction. We present a generative model that integrates the two in order to explore how variation in either might shape cultural diffusion dynamics. Agents make behavioural choices that change as they learn from their behavioural productions. Their repertoires also change over time, and the social transmission of behaviours depends on their frequency. We diffuse a novel behaviour through social networks across a large parameter space to demonstrate how accounting for both transmission and production reveals dependencies between individual-level behavioural production rules and population-level diffusion dynamics. We then investigate how such dependencies might affect the performance of two commonly used inferential models for social learning; Network-based Diffusion Analysis (NBDA), and Experienced Weighted Attraction models (EWA). By clarifying the distinction between acquisition and usage, we illuminate often-overlooked theoretical differences between social learning and social influence. These distinctions yield consequences and new considerations for how inferential methods are applied to empirical studies of culture.

Honey bee genetics shape the strain-level structure of gut microbiota in social transmission

Background Honey bee gut microbiota transmitted via social interactions are beneficial to the host health. Although the microbial community is relatively stable, individual variations and high strain-level diversity have been detected across honey bees. Although the bee gut microbiota structure is influenced by environmental factors, the heritability of the gut members and the contribution of the host genetics remains elusive. Considering bees within a colony are not readily genetically identical due to the polyandry of the queen, we hypothesize that the microbiota structure can be shaped by host genetics. Results We used shotgun metagenomics to simultaneously profile the microbiota and host genotypes of bees from hives of four different subspecies. Gut composition is more distant between genetically different bees at both phylotype- and “sequence-discrete population” levels. We then performed a successive passaging experiment within colonies of hybrid bees generated by artificial insemination, which revealed that the microbial composition dramatically shifts across batches of bees during the social transmission. Specifically, different strains from the phylotype of Snodgrassella alvi are preferentially selected by genetically varied hosts, and strains from different hosts show a remarkably biased distribution of single-nucleotide polymorphism in the Type IV pili loci. Genome-wide association analysis identified that the relative abundance of a cluster of Bifidobacterium strains is associated with the host glutamate receptor gene specifically expressed in the bee brain. Finally, mono-colonization of Bifidobacterium with a specific polysaccharide utilization locus impacts the alternative splicing of the gluR-B gene, which is associated with an increased GABA level in the brain. Conclusions Our results indicated that host genetics influence the bee gut composition and suggest a gut-brain connection implicated in the gut bacterial strain preference. Honey bees have been used extensively as a model organism for social behaviors, genetics, and the gut microbiome. Further identification of host genetic function as a shaping force of microbial structure will advance our understanding of the host-microbe interactions.

Effects of verbal instruction vs. modelling on imitation and overimitation

Human culture is the result of a unique cumulative evolutionary process. Despite the importance of culture for our species the social transmission mechanisms underlying this process are still not fully understood. In particular, the role of language—another unique human behaviour—in social transmission is under-explored. In this first direct, systematic comparison of demonstration vs. language-based social learning, we ran transmission chains of participants (6- to 8-year-old children and adults from Cyprus) who attempted to extract a reward from a puzzle box after either watching a model demonstrate an action sequence or after listening to verbal instructions describing the action sequence. The initial seeded sequences included causally relevant and irrelevant actions allowing us to measure transmission fidelity and the accumulation of beneficial modifications through the lens of a subtractive ratchet effect. Overall, we found that, compared to demonstration, verbal instruction specifically enhanced the faithful transmission of causally irrelevant actions (overimitation) in children, but not in adults. Cumulative cultural evolution requires the faithful transmission of sophisticated, complex behaviour whose function may not be obvious. This indicates that, by supporting the retention of actions that appear to lack a causal function specifically by children, language may play a supportive role in cumulative cultural evolution.

The military as a neglected pathogen transmitter and its implications for COVID-19: A systematic review

Background: The risk of outbreaks escalating into pandemics has soared with globalization. Therefore, understanding transmission mechanisms of infectious diseases has become critical to formulating global public health policy. This systematic review assessed the evidence for the military as a disease vector, an historically relevant one, yet overlooked in times of COVID-19. Methods: We searched 3 electronic databases without temporal restrictions. We identified 2010 of 6477 studies spanning over two centuries (1810 – 2020) that met our inclusion criteria and provided evidence for the military as a pathogen transmitter, within itself or between it and civilians. Two researchers independently extracted study data using a standardized form. Through team discussions, studies were grouped according to their type of transmission mechanism and direct quotes were extracted to generate themes and sub–themes. A content analysis was later performed and frequency distributions for each theme were generated. Results: Biological mechanisms driving transmission included person–to–person transmission, contaminated food and water, vector–borne, and airborne routes. Social mechanisms facilitating transmission included crowded living spaces, unhygienic conditions, strenuous working, training conditions, absent or inadequate vaccination programs, pressure from military leadership, poor compliance with public health advice, contractor mismanagement, high–risk behaviours, and occupation–specific freedom of movement. Contaminated food and/or water was the most common biological transmission route. Living conditions were the most common social transmission mechanism, with young, low ranking military personnel repeatedly reported as the most affected group. Certain social mechanisms, such as employment–related freedom of movement, were unique to the military as a social institution. While few studies explicitly studied civilian populations, considerably more contained information that implied that civilians were likely impacted by outbreaks described in the military. Conclusions: Features of the military identified in this study pose a significant public health threat, especially to countries with substantial military presence or underdeveloped health systems. Many social transmission mechanisms, unlike biological ones, were unique to the military, facilitating large–spreader events and affecting civilian health. As an increasingly interconnected world faces the challenges of COVID–19 and future infectious diseases, the identified features of the military may exacerbate current and similar challenges and impair attempts to implement successful and equitable pandemic policies.

Oxytocin regulation of social transmission of fear in zebrafish reveals its evolutionary conserved role in emotional contagion

Emotional contagion is the most ancestral form of empathy that relies on simple perception-action mechanisms, on top of which more complex forms of empathic behaviors, such as consolation and helping, have evolved. Here we tested to what extent the proximate mechanisms of emotional contagion are evolutionary conserved by assessing the role of oxytocin, known to regulate empathic behaviors in mammals, in social fear contagion in zebrafish, which represents an evolutionary divergent line to that of tetrapods, within vertebrates. Using mutants for the ligand of the fish oxytocin nonapeptide and both of its receptors in zebrafish we showed that oxytocin is necessary for observer zebrafish to copy the distressed behavior of conspecific demonstrators. Exogeneous administration of oxytocin to the ligand mutant rescued the ability of observers to express social fear transmission, indicating that oxytocin is not only necessary but also sufficient for emotional contagion. The brain regions in the ventral telencephalon that are associated with emotional contagion in zebrafish are homologous to those known to be involved in the same process in rodents (e.g. striatum, lateral septum), and receive direct projections from oxytocinergic neurons located in the preoptic area. Finally, we ruled out the hypothesis that social transmission of fear in zebrafish merely relies on behavior contagion by motor imitation, and we showed that it rather relies on emotion discrimination. Together our results support an evolutionary conserved role for oxytocin as a key regulator of basic empathic behaviors across vertebrates.

Oxytocin neurons enable social transmission of maternal behaviour

Maternal care, including by non-biological parents, is important for offspring survival1–8. Oxytocin1,2,9–15, which is released by the hypothalamic paraventricular nucleus (PVN), is a critical maternal hormone. In mice, oxytocin enables neuroplasticity in the auditory cortex for maternal recognition of pup distress15. However, it is unclear how initial parental experience promotes hypothalamic signalling and cortical plasticity for reliable maternal care. Here we continuously monitored the behaviour of female virgin mice co-housed with an experienced mother and litter. This documentary approach was synchronized with neural recordings from the virgin PVN, including oxytocin neurons. These cells were activated as virgins were enlisted in maternal care by experienced mothers, who shepherded virgins into the nest and demonstrated pup retrieval. Virgins visually observed maternal retrieval, which activated PVN oxytocin neurons and promoted alloparenting. Thus rodents can acquire maternal behaviour by social transmission, providing a mechanism for adapting the brains of adult caregivers to infant needs via endogenous oxytocin.

Investigating the factors that contributes most to the virality of a social media video advertisement

YouTube has emerged as a very popular advertising medium in the past few years. Many marketers use this platform as a launch pad for their branding campaign. However, success is not always guaranteed with some advertisements gaining major traction whilst others’ effectiveness becomes questionable with poor traction. Thus, we are aware that social transmission is frequent and important but researchers are not yet clear about why certain content is more viral than others (Berger and Milkman 2011). In this research, we attempt to sift out the factors that contribute most to the ‘virality’ of any advertisement. We define virality as the average of likes, comments, dislikes, shares and hits for the advertisement. Our research builds up further on other research such as Berger and Milkman (2011) and Godes and Mayzlin (2009) within the Indian context by initially identifying 18 themes that were most commonly found in the advertisements here. The sample for identifying the themes was obtained from Youtube and was marked by 20 respondents on a scale of 1 to 7 based upon the degree of presence of the themes identified. Regression, factor analysis and a confirmatory factor analysis were conducted to finally arrive at a list of 7 factors. Though the adjusted R-square value was on the lower side as is the case in most such studies, our exploratory research is one of the first few such studies conducted within the Indian context and adds to our knowledge on virality in online advertising.

Social transmission in the wild can reduce predation pressure on novel prey signals

Social transmission of information is taxonomically widespread and could have profound effects on the ecological and evolutionary dynamics of animal communities. Demonstrating this in the wild, however, has been challenging. Here we show by field experiment that social transmission among predators can shape how selection acts on prey defences. Using artificial prey and a novel approach in statistical analyses of social networks, we find that blue tit (Cyanistes caeruleus) and great tit (Parus major) predators learn about prey defences by watching others. This shifts population preferences rapidly to match changes in prey profitability, and reduces predation pressure from naïve predators. Our results may help resolve how costly prey defences are maintained despite influxes of naïve juvenile predators, and suggest that accounting for social transmission is essential if we are to understand coevolutionary processes.