Over the last ten years, Oosterhof and Todorov's valence-dominance model has emerged as the most prominent account of how people evaluate faces on social dimensions. In this model, two dimensions (valence and dominance) underpin social judgments of faces. Because this model has primarily been developed and tested in Western regions, it is unclear whether these findings apply to other regions. We addressed this question by replicating Oosterhof and Todorov's methodology across 11 world regions, 41 countries, and 11,570 participants. When we used Oosterhof and Todorov's original analysis strategy, the valence-dominance model generalized across regions. When we used an alternative methodology to allow for correlated dimensions we observed much less generalization. Collectively, these results suggest that, while the valence-dominance model generalizes very well across regions when dimensions are forced to be orthogonal, regional differences are revealed when we use different extraction methods, correlate and rotate the dimension reduction solution.

There is considerable variation in health and reproductive behaviours within and across human populations. Drawing on principles from Life History Theory, psychosocial acceleration theory predicts that individuals developing in harsh environments decrease their level of somatic investment and accelerate their reproductive schedule. Although there is consistent empirical support for this general prediction, most studies have focused on a few isolated life history traits and few have investigated the way in which individuals apply life strategies across reproductive and somatic domains to produce coordinated behavioural responses to their environment. In our study, we thus investigate the impact of childhood environmental harshness on both reproductive strategies and somatic investment by applying structural equation modeling (SEM) to cross-sectional survey data obtained in a representative sample of the French population (n = 1015, age: 19-87 years old, both genders). This data allowed us to demonstrate that (i) inter-individual variation in somatic investment (e.g. effort in looking after health) and reproductive timing (e.g. age at first birth) can be captured by a latent fast-slow continuum, and (ii) faster strategies along this continuum are predicted by higher childhood harshness. Overall, our results support the existence of a fast-slow continuum and highlight the relevance of the life history approach for understanding variations in reproductive and health related behaviours.

We offer three recommendations to increase COVID-19 vaccination rates. First, use communication campaigns leveraging evidence-based levers and argumentation tools with experts. Second, use behavioral insights to make vaccination more accessible. Third, help early adopters communicate about their decision to be vaccinated to accelerate the emergence of pro-vaccination norms.

A safe and effective COVID-19 vaccine is our only hope to decisively stop the spread of the SARS-CoV-2. But a vaccine will only be fully effective if a significant share of the population agrees to get it. Five consecutive surveys of a large, nationally representative sample (N = 1000 for each wave) surveyed attitudes towards a future COVID-19 vaccine in France from May 2020 to October 2020. We found that COVID-19 vaccine refusal has steadily increased, reaching an all-time high with only 23% of participants willing to probably or certainly take a future COVID-19 vaccine in September 2020. Vaccine hesitant individuals are more likely to be women, young, less educated, to vote at the political extremes, to be dissatisfied with the government’s response to the COVID-19 crisis, and to feel less at risk of COVID-19. The reasons why French people would refuse to take the COVID-19 vaccine are similar to those offered for other vaccines, and these reasons are strikingly stable across gender, age and educational level. Finally, most French people declare they would not take the vaccine as soon as possible but would instead rather wait or not take it at all.

The Coronavirus disease; COVID-19 vaccines will not end the pandemic if they stay in freezers. In many countries, such as France, COVID-19 vaccines hesitancy is high. It is crucial that governments make it as easy as possible for people who want to be vaccinated to do so, but also that they devise communication strategies to address the concerns of vaccine hesitant individuals. We introduce and test on 701 French participants a novel messaging strategy: A chatbot that answers people's questions about COVID-19 vaccines. We find that interacting with this chatbot for a few minutes significantly increases people's intentions to get vaccinated (ß = 0.12) and has a positive impact on their attitudes toward COVID-19 vaccination (ß = 0.23). Our results suggest that a properly scripted and regularly updated chatbot could offer a powerful resource to help fight hesitancy toward COVID-19 vaccines. Public Significance StatementInteracting a few minutes with a chatbot answering the most common questions about COVID-19 vaccines increased people's intention to get vaccinated and had a positive impact on their attitudes toward the vaccines. Chatbots could be a powerful resource to fight COVID-19 vaccines hesitancy.

Social trust is linked to a host of positive societal outcomes, including improved economic performance, lower crime rates and more inclusive institutions. Yet, the origins of trust remain elusive, partly because social trust is difficult to document in time. Building on recent advances in social cognition, we design an algorithm to automatically generate trustworthiness evaluations for the facial action units (smile, eye brows, etc.) of European portraits in large historical databases. Our results show that trustworthiness in portraits increased over the period 1500–2000 paralleling the decline of interpersonal violence and the rise of democratic values observed in Western Europe. Further analyses suggest that this rise of trustworthiness displays is associated with increased living standards.

Public health communication play an important role in the fight against COVID-19. We used five well-established psychological levers to improve on the efficacy of two posters used by the French authorities (one on protective behaviors and one on proper handwashing). The five levers were: simplification (streamlining the posters), sunk costs (emphasizing the costs already paid to fight the pandemic), morality (emphasizing the duty to help others), self-protection (emphasizing the personal risks), and disgust (pointing out and illustrating that not following the protective behaviors or proper handwashing had consequences that should trigger disgust). We tested on a large (N = 3000) nationally representative French sample whether versions of the posters using these levers, compared to a control condition, were clearer, better recalled, and increased people’s intention to follow the posters’ recommendations. On the whole, there were no effects of the manipulations on any of the measures. The only consistent pattern was that the control protective behavior poster was better recalled than the alternatives (except for the simplified version), possibly because it contained one fewer message. The lack of effect on behavioral intentions might be attributed to the potential saturation in terms of health communication at the time of the experiment. Our results--mostly null and potentially negative--confirm the importance of testing interventions before using them in a public health campaign, even if they are grounded in successful past interventions.

Why do moral religions exist? An influential psychological explanation is that religious beliefs in supernatural punishment is cultural group adaptation enhancing prosocial attitudes and thereby large-scale cooperation. An alternative explanation is that religiosity is an individual strategy that results from high level of mistrust and the need for individuals to control others’ behaviors through moralizing. Existing evidence is mixed but most works are limited by sample size and generalizability issues. The present study overcomes these limitations by applying k-fold cross-validation on multivariate modeling of data from >295,000 individuals in 108 countries of the World Values Surveys and the European Value Study. First, this methodology reveals no evidence that European and non-European religious people invest more in collective actions and are more trustful of unrelated conspecifics. Instead, the individuals’ level of religiosity is found to be weakly but positively associated with social mistrust and negatively associated with the production of behaviors, which benefit unrelated members of the large-scale community. Second, our models show that individual variation in religiosity is well explained by the interaction of increased levels of social mistrust and increased needs to moralize other people’s sexual behaviors. Finally, stratified k-fold cross-validation demonstrates that the structures of these association patterns are robust to sampling variability and reliable enough to generalize to out-of-sample data.