Space and rank: infants expect agents in higher position to be socially dominant.

Social hierarchies exist throughout the animal kingdom, including among humans. Our daily interactions inevitably reflect social dominance relationships between individuals. How do we mentally represent such concepts? Studies show that social dominance is represented as vertical space (i.e. high = dominant) by adults and preschool children, suggesting a space-dominance representational link in social cognition. However, little is known about its early development. Here, we present experimental evidence that 12- to 16-month-old infants expect agents presented in a higher spatial position to be more socially dominant than agents in a lower spatial position. After infants repeatedly watched the higher and lower agents being presented simultaneously, they looked longer at the screen when the lower agent subsequently outcompeted the higher agent in securing a reward object, suggesting that this outcome violated their higher-is-dominant expectation. We first manipulated agents' positions by presenting them on a podium (experiment 1). Then we presented the agents on a double-decker stand to make their spatial positions directly above or below each other (experiment 2), and we replicated the results (experiment 3). This research demonstrates that infants expect spatially higher-positioned agents to be socially dominant, suggesting deep roots of the space-dominance link in ontogeny.

The evolution of the shaman's cultural toolkit.

A complete picture of shamanism's cultural evolution requires an understanding of how the professionalization of shamanism affects the distribution of knowledge within societies. We suggest that limiting knowledge to fewer people could impede the accumulation of functional knowledge within shamanism. On this basis, we make further predictions about how the domain of shamanism could change and collapse.

Two distinct neural mechanisms underlying indirect reciprocity.

Cooperation is a hallmark of human society. Humans often cooperate with strangers even if they will not meet each other again. This so-called indirect reciprocity enables large-scale cooperation among nonkin and can occur based on a reputation mechanism or as a succession of pay-it-forward behavior. Here, we provide the functional and anatomical neural evidence for two distinct mechanisms governing the two types of indirect reciprocity. Cooperation occurring as reputation-based reciprocity specifically recruited the precuneus, a region associated with self-centered cognition. During such cooperative behavior, the precuneus was functionally connected with the caudate, a region linking rewards to behavior. Furthermore, the precuneus of a cooperative subject had a strong resting-state functional connectivity (rsFC) with the caudate and a large gray matter volume. In contrast, pay-it-forward reciprocity recruited the anterior insula (AI), a brain region associated with affective empathy. The AI was functionally connected with the caudate during cooperation occurring as pay-it-forward reciprocity, and its gray matter volume and rsFC with the caudate predicted the tendency of such cooperation. The revealed difference is consistent with the existing results of evolutionary game theory: although reputation-based indirect reciprocity robustly evolves as a self-interested behavior in theory, pay-it-forward indirect reciprocity does not on its own. The present study provides neural mechanisms underlying indirect reciprocity and suggests that pay-it-forward reciprocity may not occur as myopic profit maximization but elicit emotional rewards.

Exploring new technologies for the future generation: exploration-exploitation trade-off in an intergenerational framework.

Decision making on exploring or exploiting technology was studied by means of a laboratory experiment with a two-generation framework. In this framework, the design of a virtual tool is transmitted from the first to second generation, and hence, the former can help the latter by frequently exploring better tool designs but at the cost of reduced opportunities to exploit the existing tool to increase its own benefits. We set two experimental conditions ('repaid' and 'unrepaid') as well as a control condition (asocial), in which the second generation is absent. In the 'repaid' experimental condition, participants received an extra payment proportional to the score gained by the second generation, such that they were monetarily incentivized to help the second generation. Such an incentive was not given in the 'unrepaid' condition. An analysis of a formal model and computer simulations predicted that rational participants should increase investment in exploration only in the repaid condition when compared with the asocial control. The prediction was confirmed by the results of the experiment. These findings together suggest that humans may not have a propensity to invest in costly exploration of new technologies solely to help future generations.

Biogeographical |distributions of trickster animals.

Human language encompasses almost endless potential for meaning, and folklore can theoretically incorporate themes beyond time and space. However, actual distributions of the themes are not always universal and their constraints remain unclear. Here, we specifically focused on zoological folklore and aimed to reveal what restricts the distribution of trickster animals in folklore. We applied the biogeographical methodology to 16 taxonomic categories of trickster (455 data) and real (93 090 848 data) animals obtained from large databases. Our analysis revealed that the distribution of trickster animals was restricted by their presence in the vicinity and, more importantly, the presence of their corresponding real animals. Given that the distributions of real animals are restricted by the annual mean temperature and annual precipitation, these climatic conditions indirectly affect the distribution of trickster animals. Our study, applying biogeographical methods to culture, paves the way to a deeper understanding of the interactions between ecology and culture.

Children attribute higher social status to people who have extraordinary capabilities.

Throughout history, individuals believed to have extraordinary capabilities were generally highly ranked in their communities; this suggests a universal "extraordinary-dominant expectation" in human minds, which may play a key role in religious thought, even in modern societies. This study shows that 5-6-year-old children, who begin to understand real-world causalities regarding how the body and mind of human beings work, predict that individuals who exhibit extraordinary capabilities have higher social status in interactions with individuals who exhibit ordinary capabilities. In Experiment 1, we showed children two individuals achieving goals using either humanly possible or impossible methods, the latter involving simple forms of violation of intuitive psychology (knowing without seeing), physics (flying), or biology (fire breathing). The children clearly judged the latter as surprising and unusual. More importantly, the children predicted that individuals showing extraordinary capabilities will gain contested resources and play a dominant role in interactions with ordinary individuals, indicating a higher social status. Further investigations suggested that the children specifically linked extraordinary capacities to social status, as they did not attribute dominance to individuals who apply surprising/unusual but possible methods (Experiment 2), and that they did not indiscriminately attribute positive characteristics to extraordinary capabilities despite a strong extraordinary-dominant expectation being replicated (Experiment 3). These findings demonstrate that extraordinary-dominant expectations can be observed in childhood across different intuitive knowledge domains, helping understand the cognitive mechanisms of religious thought and the cognitive foundations of hierarchical social systems.

Negative observational learning might play a limited role in the cultural evolution of technology.

Theoretical and empirical studies of the cultural evolution in technology have often focused on positive observational learning, i.e., copying a successful individual. However, negative observational learning, i.e., avoiding negative or bad exemplar behavior, is ubiquitous in humans and other animals. In this paper, we experimentally investigate whether observing negative examples can assist in tool making in the virtual arrowhead task, which has been widely applied to test the theory of cultural evolution in the technological domain. We set three conditions that differ in the kinds of social learning available to participants: (1) positive observational learning, (2) negative observational learning, and (3) pure asocial learning. The results of the positive observational and pure asocial learning conditions replicated previous studies; i.e., participants in the positive observational learning condition outperformed those in the asocial learning condition. In contrast, opportunities to observe negative examples did not increase the performance compared to pure asocial learning. Computer simulations in the same setting showed that the presence of negative exemplars is in theory beneficial to participants, providing additional pieces of information on the relationship between arrowhead designs and their performance scores. These findings together suggest that negative observational learning might play only a limited role in the cultural evolution of technologies possibly due to a cognitive bias in humans toward copying.

Salivary Oxytocin Is Negatively Associated With Religious Faith in Japanese Non-Abrahamic People.

Spirituality and religiosity have a significant impact on one's well-being. Although previous studies have indicated that the neuropeptide hormone oxytocin is associated with spirituality/religiosity, existing findings remain inconsistent. Some studies have reported a positive relationship between oxytocin and spirituality/religiosity, while other studies have reported a negative association. Herein, we examined the association between endogenous oxytocin and spirituality/religiosity in 200 non-Abrahamic Japanese individuals (102 females, mean age ± standard deviation = 41.53 ± 10.46) by measuring the level of salivary oxytocin and spiritual/religious faith. We found that the level of salivary oxytocin was negatively associated with spiritual/religious faith. Individuals with higher levels of salivary oxytocin tend to have more negative spiritual/religious faith compared with those with low oxytocin levels (e.g., "Spirituality/religiosity makes people passive and clinging."). Moreover, this tendency was only significant in individuals who were not interested in a specific religion. The uniqueness of spirituality/religiosity in Japan could help interpret the current findings.

Preverbal infants expect agents exhibiting counterintuitive capacities to gain access to contested resources.

Claims to supernatural power have been used as a basis for authority in a wide range of societies, but little is known about developmental origins of the link between supernatural power and worldly authority. Here, we show that 12- to 16-month-old infants expect agents exhibiting counterintuitive capacities to win out in a two-way standoff over a contested resource. Infants watched two agents gain a reward using either physically intuitive or physically counterintuitive methods, the latter involving simple forms of levitation or teleportation. Infants looked longer, indicating surprise, when the physically intuitive agent subsequently outcompeted a physically counterintuitive agent in securing a reward. Control experiments indicated that infants' expectations were not simply motived by the efficiency of agents in pursuing their goals, but specifically the deployment of counterintuitive capacities. This suggests that the link between supernatural power and worldly authority has early origins in development.

Transient nature of cooperation by pay-it-forward reciprocity.

Humans often forward kindness received from others to strangers, a phenomenon called the upstream or pay-it-forward indirect reciprocity. Some field observations and laboratory experiments found evidence of pay-it-forward reciprocity in which chains of cooperative acts persist in social dilemma situations. Theoretically, however, cooperation based on pay-it-forward reciprocity is not sustainable. We carried out laboratory experiments of a pay-it-forward indirect reciprocity game (i.e., chained gift-giving game) on a large scale in terms of group size and time. We found that cooperation consistent with pay-it-forward reciprocity occurred only in a first few decisions per participant and that cooperation originated from inherent pro-sociality of individuals. In contrast, the same groups of participants showed persisting chains of cooperation in a different indirect reciprocity game in which participants earned reputation by cooperating. Our experimental results suggest that pay-it-forward reciprocity is transient and disappears when a person makes decisions repeatedly, whereas the reputation-based reciprocity is stable in the same situation.