Historical narratives about the COVID-19 pandemic are motivationally biased.

How people recall the SARS-CoV-2 pandemic is likely to prove crucial in future societal debates on pandemic preparedness and appropriate political action. Beyond simple forgetting, previous research suggests that recall may be distorted by strong motivations and anchoring perceptions on the current situation1-6. Here, using 4 studies across 11 countries (total n = 10,776), we show that recall of perceived risk, trust in institutions and protective behaviours depended strongly on current evaluations. Although both vaccinated and unvaccinated individuals were affected by this bias, people who identified strongly with their vaccination status-whether vaccinated or unvaccinated-tended to exhibit greater and, notably, opposite distortions of recall. Biased recall was not reduced by providing information about common recall errors or small monetary incentives for accurate recall, but was partially reduced by high incentives. Thus, it seems that motivation and identity influence the direction in which the recall of the past is distorted. Biased recall was further related to the evaluation of past political action and future behavioural intent, including adhering to regulations during a future pandemic or punishing politicians and scientists. Together, the findings indicate that historical narratives about the COVID-19 pandemic are motivationally biased, sustain societal polarization and affect preparation for future pandemics. Consequently, future measures must look beyond immediate public-health implications to the longer-term consequences for societal cohesion and trust.

Heterogeneity in effect size estimates.

A typical empirical study involves choosing a sample, a research design, and an analysis path. Variation in such choices across studies leads to heterogeneity in results that introduce an additional layer of uncertainty, limiting the generalizability of published scientific findings. We provide a framework for studying heterogeneity in the social sciences and divide heterogeneity into population, design, and analytical heterogeneity. Our framework suggests that after accounting for heterogeneity, the probability that the tested hypothesis is true for the average population, design, and analysis path can be much lower than implied by nominal error rates of statistically significant individual studies. We estimate each type's heterogeneity from 70 multilab replication studies, 11 prospective meta-analyses of studies employing different experimental designs, and 5 multianalyst studies. In our data, population heterogeneity tends to be relatively small, whereas design and analytical heterogeneity are large. Our results should, however, be interpreted cautiously due to the limited number of studies and the large uncertainty in the heterogeneity estimates. We discuss several ways to parse and account for heterogeneity in the context of different methodologies.

Social mindfulness and prosociality vary across the globe.

Humans are social animals, but not everyone will be mindful of others to the same extent. Individual differences have been found, but would social mindfulness also be shaped by one's location in the world? Expecting cross-national differences to exist, we examined if and how social mindfulness differs across countries. At little to no material cost, social mindfulness typically entails small acts of attention or kindness. Even though fairly common, such low-cost cooperation has received little empirical attention. Measuring social mindfulness across 31 samples from industrialized countries and regions (n = 8,354), we found considerable variation. Among selected country-level variables, greater social mindfulness was most strongly associated with countries' better general performance on environmental protection. Together, our findings contribute to the literature on prosociality by targeting the kind of everyday cooperation that is more focused on communicating benevolence than on providing material benefits.

Economic games for the study of peace.

Economic games provide models of real-world contexts in which researchers can probe dispositional and structural determinants of intergroup relations. Most intergroup games focus on determinants of aggression between groups and constrain the possibilities for peace. However, paradigms such as the intergroup parochial and universal cooperation game allow for peaceful intergroup relations and can be adapted for the study of peace.

Voluntary restrictions on self-reliance increase cooperation and mitigate wealth inequality.

Humans are considered a highly cooperative species. Through cooperation, we can tackle shared problems like climate change or pandemics and cater for shared needs like shelter, mobility, or healthcare. However, cooperation invites free-riding and can easily break down. Maybe because of this reason, societies also enable individuals to solve shared problems individually, like in the case of private healthcare plans or private retirement planning. Such "self-reliance" allows individuals to avoid problems related to public goods provision, like free-riding or underprovision, and decreases social interdependence. However, not everyone can equally afford to be self-reliant, and amid shared problems, self-reliance may lead to conflicts within groups on how to solve shared problems. In two preregistered studies, we investigate how the ability of self-reliance influences collective action and cooperation. We show that self-reliance crowds out cooperation and exacerbates inequality, especially when some heavily depend on collective action while others do not. However, we also show that groups are willing to curtail their ability of self-reliance. When given the opportunity, groups overwhelmingly vote in favor of abolishing individual solutions to shared problems, which, in turn, increases cooperation and decreases inequality, particularly between group members that differ in their ability to be self-reliant. The support for such endogenously imposed interdependence, however, reduces when individual solutions become more affordable, resonating with findings of increased individualism in wealthier societies and suggesting a link between wealth inequality and favoring individual independence and freedom over communalism and interdependence.

Vaccination as a social contract.

Most vaccines protect both the vaccinated individual and the society by reducing the transmission of infectious diseases. In order to eliminate infectious diseases, individuals need to consider social welfare beyond mere self-interest-regardless of ethnic, religious, or national group borders. It has therefore been proposed that vaccination poses a social contract in which individuals are morally obliged to get vaccinated. However, little is known about whether individuals indeed act upon this social contract. If so, vaccinated individuals should reciprocate by being more generous to a vaccinated other. On the contrary, if the other doesn't vaccinate and violates the social contract, generosity should decline. Three preregistered experiments investigated how a person's own vaccination behavior, others' vaccination behavior, and others' group membership influenced a person's generosity toward respective others. The experiments consistently showed that especially compliant (i.e., vaccinated) individuals showed less generosity toward nonvaccinated individuals. This effect was independent of the others' group membership, suggesting an unconditional moral principle. An internal metaanalysis (n = 1,032) confirmed the overall social contract effect. In a fourth experiment (n = 1,212), this pattern was especially pronounced among vaccinated individuals who perceived vaccination as a moral obligation. It is concluded that vaccination is a social contract in which cooperation is the morally right choice. Individuals act upon the social contract, and more so the stronger they perceive it as a moral obligation. Emphasizing the social contract could be a promising intervention to increase vaccine uptake, prevent free riding, and, eventually, support the elimination of infectious diseases.

Social and behavioral consequences of mask policies during the COVID-19 pandemic.

Mandatory and voluntary mask policies may have yet unknown social and behavioral consequences related to the effectiveness of the measure, stigmatization, and perceived fairness. Serial cross-sectional data (April 14 to May 26, 2020) from nearly 7,000 German participants demonstrate that implementing a mandatory policy increased actual compliance despite moderate acceptance; mask wearing correlated positively with other protective behaviors. A preregistered experiment (n = 925) further indicates that a voluntary policy would likely lead to insufficient compliance, would be perceived as less fair, and could intensify stigmatization. A mandatory policy appears to be an effective, fair, and socially responsible solution to curb transmissions of airborne viruses.

Information nudges for influenza vaccination: Evidence from a large-scale cluster-randomized controlled trial in Finland.

BACKGROUND: Vaccination is the most effective means of preventing the spread of infectious diseases. Despite the proven benefits of vaccination, vaccine hesitancy keeps many people from getting vaccinated. METHODS AND FINDINGS: We conducted a large-scale cluster randomized controlled trial in Finland to test the effectiveness of centralized written reminders (distributed via mail) on influenza vaccination coverage. The study included the entire older adult population (aged 65 years and above) in 2 culturally and geographically distinct regions with historically low (31.8%, n = 7,398, mean age 75.5 years) and high (57.7%, n = 40,727, mean age 74.0 years) influenza vaccination coverage. The study population was randomized into 3 treatments: (i) no reminder (only in the region with low vaccination coverage); (ii) an individual-benefits reminder, informing recipients about the individual benefits of vaccination; and (iii) an individual- and social-benefits reminder, informing recipients about the additional social benefits of vaccination in the form of herd immunity. There was no control treatment group in the region with high vaccination coverage as general reminders had been sent in previous years. The primary endpoint was a record of influenza vaccination in the Finnish National Vaccination Register during a 5-month follow-up period (from October 18, 2018 to March 18, 2019). Vaccination coverage after the intervention in the region with historically low coverage was 41.8% in the individual-benefits treatment, 38.9% in the individual- and social-benefits treatment and 34.0% in the control treatment group. Vaccination coverage after the intervention in the region with historically high coverage was 59.0% in the individual-benefits treatment and 59.2% in the individual- and social-benefits treatment. The effect of receiving any type of reminder letter in comparison to control treatment group (no reminder) was 6.4 percentage points (95% CI: 3.6 to 9.1, p < 0.001). The effect of reminders was particularly large among individuals with no prior influenza vaccination (8.8 pp, 95% CI: 6.5 to 11.1, p < 0.001). There was a substantial positive effect (5.3 pp, 95% CI: 2.8 to 7.8, p < 0.001) among the most consistently unvaccinated individuals who had not received any type of vaccine during the 9 years prior to the study. There was no difference in influenza vaccination coverage between the individual-benefit reminder and the individual- and social-benefit reminder (region with low vaccination coverage: 2.9 pp, 95% CI: -0.4 to 6.1, p = 0.087, region with high vaccination coverage: 0.2 pp, 95% CI: -1.0 to 1.3, p = 0.724). Study limitations included potential contamination between the treatments due to information spillovers and the lack of control treatment group in the region with high vaccination coverage. CONCLUSIONS: In this study, we found that sending reminders was an effective and scalable intervention strategy to increase vaccination coverage in an older adult population with low vaccination coverage. Communicating the social benefits of vaccinations, in addition to individual benefits, did not enhance vaccination coverage. The effectiveness of letter reminders about the benefits of vaccination to improve influenza vaccination coverage may depend on the prior vaccination history of the population. TRIAL REGISTRATION: AEA RCT registry AEARCTR-0003520 and ClinicalTrials.gov NCT03748160.

Sensitive attitudes and adherence to recommendations during the COVID-19 pandemic: Comparing direct and indirect questioning techniques.

During the COVID-19 pandemic, various behavioral measures were imposed to curb the spread of the virus. In a preregistered study based on a quota-representative sample of adult Danish citizens (N = 1031), we compared the prevalence estimates of self-reported handwashing, physical distancing, and attitudes toward the behavioral measures between people surveyed with a direct and an indirect questioning approach (i.e., the crosswise model). Moreover, we investigated two possible predictors of sensitive behaviors and attitudes, namely empathy for people vulnerable to the virus and Honesty-Humility from the HEXACO Model of Personality. We also examined the interaction of both predictors with the questioning format. Survey participants reported more violation of guidelines regarding handwashing and physical distancing when asked indirectly rather than directly, whereas attitudes regarding the behavioral measures did not differ between the two questioning formats. Respondents with less empathy for people vulnerable to COVID-19 reported more violations of handwashing and physical-distancing, and those low on Honesty-Humility reported more violations of physical distancing.

Costs, needs, and integration efforts shape helping behavior toward refugees.

Recent political instabilities and conflicts around the world have drastically increased the number of people seeking refuge. The challenges associated with the large number of arriving refugees have revealed a deep divide among the citizens of host countries: one group welcomes refugees, whereas another rejects them. Our research aim is to identify factors that help us understand host citizens' (un)willingness to help refugees. We devise an economic game that captures the basic structural properties of the refugee situation. We use it to investigate both economic and psychological determinants of citizens' prosocial behavior toward refugees. In three controlled laboratory studies, we find that helping refugees becomes less likely when it is individually costly to the citizens. At the same time, helping becomes more likely with the refugees' neediness: helping increases when it prevents a loss rather than generates a gain for the refugees. Moreover, particularly citizens with higher degrees of prosocial orientation are willing to provide help at a personal cost. When refugees have to exert a minimum level of effort to be eligible for support by the citizens, these mandatory "integration efforts" further increase prosocial citizens' willingness to help. Our results underscore that economic factors play a key role in shaping individual refugee helping behavior but also show that psychological factors modulate how individuals respond to them. Moreover, our economic game is a useful complement to correlational survey measures and can be used for pretesting policy measures aimed at promoting prosocial behavior toward refugees.

The four weeks before lockdown during the COVID-19 pandemic in Germany: a weekly serial cross-sectional survey on risk perceptions, knowledge, public trust and behaviour, 3 to 25 March 2020.

BackgroundDuring the COVID-19 pandemic, public perceptions and behaviours have had to adapt rapidly to new risk scenarios and radical behavioural restrictions.AimTo identify major drivers of acceptance of protective behaviours during the 4-week transition from virtually no COVID-19 cases to the nationwide lockdown in Germany (3-25 March 2020).MethodsA serial cross-sectional online survey was administered weekly to ca 1,000 unique individuals for four data collection rounds in March 2020 using non-probability quota samples, representative of the German adult population between 18 and 74 years in terms of age × sex and federal state (n = 3,910). Acceptance of restrictions was regressed on sociodemographic variables, time and psychological variables, e.g. trust, risk perceptions, self-efficacy. Extraction of homogenous clusters was based on knowledge and behaviour.ResultsAcceptance of restrictive policies increased with participants' age and employment in the healthcare sector; cognitive and particularly affective risk perceptions were further significant predictors. Acceptance increased over time, as trust in institutions became more relevant and trust in media became less relevant. The cluster analysis further indicated that having a higher education increased the gap between knowledge and behaviour. Trust in institutions was related to conversion of knowledge into action.ConclusionIdentifying relevant principles that increase acceptance will remain crucial to the development of strategies that help adjust behaviour to control the pandemic, possibly for years to come. Based on our findings, we provide operational recommendations for health authorities regarding data collection, health communication and outreach.

The Emotional Path to Action: Empathy Promotes Physical Distancing and Wearing of Face Masks During the COVID-19 Pandemic.

The COVID-19 pandemic presents a major challenge to societies all over the globe. Two measures implemented in many countries to curb the spread of the disease are (a) minimizing close contact between people ("physical distancing") and (b) wearing of face masks. In the present research, we tested the idea that physical distancing and wearing of face masks can be the result of a prosocial emotional process-empathy for people most vulnerable to the virus. In four preregistered studies (N = 3,718, Western population), we found that (a) empathy indeed relates to the motivation to adhere to physical distancing and to wearing face masks and (b) inducing empathy for people most vulnerable to the virus promotes the motivation to adhere to these measures (whereas merely providing information about the importance of the measures does not). In sum, the present research provides a better understanding of the factors underlying the willingness to follow two important measures during the COVID-19 pandemic.

Individual preferences for voluntary vs. mandatory vaccination policies: an experimental analysis.

BACKGROUND: More and more countries are discussing the introduction of mandatory vaccination policies. Yet, little is known about individuals' actual preferences for voluntary vs. mandatory vaccination policies, and the psychological processes underlying such preferences. Objective of the present research was to investigate the development of individual preferences for voluntary and mandatory vaccination policies. METHODS: We conducted a controlled laboratory study (N = 168) using a repeated interactive vaccination game with decision-contingent monetary incentives. In each round, participants decided in favour of either a voluntary or a mandatory vaccination policy, followed by the vaccination decision (voluntary policy) or vaccination (mandatory policy) which both resulted in actual (financial) consequences. RESULTS: We observe large heterogeneity in participants' preferences for the voluntary vs. mandatory policy. Under voluntary vaccination, the preference for the mandatory policy increased with decreasing vaccination rates (and increasing risk of infection). In contrast, experiencing vaccine-adverse events under mandatory vaccination increased the preference for the voluntary policy. The latter effect was larger for individuals with a negative (vs. positive) attitude toward vaccination. Overall, as individuals gathered experiences under both the voluntary and the mandatory policy, the preference for voluntary vaccination policy increased over time. CONCLUSIONS: Individuals are more willing to accept mandatory vaccination policies when vaccination rates are low. In the long run, the occurrence of vaccine-adverse events may spark opposition to mandatory vaccination.

The willingness to vaccinate increases when vaccination protects others who have low responsibility for not being vaccinated.

Vaccination provides direct protection for the vaccinating individual and indirect protection for other, unvaccinated individuals via herd immunity. Still, some people do not get vaccinated-either because they cannot (e.g., due to health conditions) or they don't want to (e.g., due to vaccine hesitancy). We investigate whether non-vaccinators' level of responsibility for not being vaccinated affects individuals' motivation to vaccinate and, thus, to indirectly protect non-vaccinators. In Study 1 (N = 101), the intention to vaccinate increased (Cohen's d = 0.99) when non-vaccinators were described as willing but unable to get vaccinated (low responsibility) compared to when they were able but unwilling to get vaccinated (high responsibility). Study 2 (N = 297) replicated this finding with regard to vaccination behavior in an interactive vaccination (I-Vax) game (OR = 2.38). Additionally, knowing about non-vaccinators' low responsibility also increased the willingness to vaccinate compared to when there was no information on non-vaccinators' level of responsibility. Amplified levels of social welfare concerns in the case of non-vaccinators' low responsibility mediated the latter effect. This finding informs effective communication strategies for improving the vaccination rates.

A note on the endogeneity of attacker and defender roles in asymmetric conflicts.

We argue that the roles of attacker and defender in asymmetric intergroup conflict are structurally ambiguous and their perception is likely to be subjectively biased. Although this allows for endogenous selection into each role, we argue that claiming the role of the defender likely is more advantageous for conflict participants.