Using a sample of 80 countries and political regions, the present study examines the effect parasite stress has on people's trust towards ingroup and outgroup members. The findings do not offer support of there being a concave relationship between parasite stress and ingroup member trust. The results do indicate that there is a U-correlation between trusting outgroup members and parasite stress.

This study tests the relationship between group morality and hostility towards outgroups. Cross-cultural findings support the hypothesis that ingroup loyalty is associated with a greater emphasis on outgroup violence. Results from a second psychological study are included and also support the hypothesis.

This article employs cross-national and cross-cultural methods to investigate whether pathogen stress is a direct determinant of authoritarianism. The study controls on other factors such as famine, warfare, and malnutrition and evaluates alternative causal models.

This paper proposes that the socio-cultural values of countries may be associated with increased mortality due to COVID-19. Using results from the World Values survey, the author assessed which values had the strongest association with a change in COVID-19 mortality in datasets consisting of all countries, upper-middle and high income economies, upper-middle income economies, high income economies, and advanced economies. The author also sought to determine whether the WVS values that were associated with COVID-19 mortality were also associated with general life expectancy. The results showed that COVID-19 mortality was increased in countries that placed a higher value on freedom of speech, political participation, religion, technocracy, post-materialism, social tolerance, law and order, and acceptance of authority. On the other hand, mortality was decreased in countries with high trust in major companies and institutions and that endorsed maintenance of order as a goal for a country. The author also found that values related to COVID-19 mortality did not predict general health outcomes, and that some values that predicted increased COVID-19 mortality actually predicted decreased mortality from other outcomes.

This study examines the relationship between population pressure and socioeconomic complexity in a cross-cultural sample of hunter-gatherer groups. The author suggests a causal component to the positive correlations found, arguing that increasing population pressure on food resources requires increasing storage dependence, which in turn drives sedentism and other indicators of socioeconomic complexity.

This article considers the consequences of modernization. Factor analysis is used to identify four stages of modernization: 1) changes in education, government, and trade; 2) changes in health, technology, and transportation; 3) changes in family, religion, and toilet; and 4) changes in behavior. The authors then consider five trends they expect to be associated with modernization and test whether they develop over the course of the four stages. Results indicate that these 5 trends—increased cultural complexity, female status, pacification, suicide, and social stress—are associated with only the first and fourth stages.

This article employs cross-national and cross-cultural methods to investigate whether pathogen stress is a direct determinant of authoritarianism. The study controls on other factors such as famine, warfare, and malnutrition and evaluates alternative causal models.

Researchers tested the popular identity fusion theory, which states that while maintaining one’s own individual identity, a deep affinity with one’s group can contribute to sacrifice for that group, in conjunction with their own hypotheses, using a behavior economic experiment. The experiment looked at whether after rolling a die to determine which cup a coin was placed into, participants actually followed the rules, or favored themselves (by putting the coin into their own cups at a disproportionate rate). The findings state that while on average, the individual participants did indeed favor themselves, those with higher ingroup fusion were more likely to sacrifice coins to other members of their ‘ingroup.' The experiments were conducted in 8 culturally diverse field sites.

This article considers the consequences of modernization. Factor analysis is used to identify four stages of modernization: 1) changes in education, government, and trade; 2) changes in health, technology, and transportation; 3) changes in family, religion, and toilet; and 4) changes in behavior. The authors then consider five trends they expect to be associated with modernization and test whether they develop over the course of the four stages. Results indicate that these 5 trends—increased cultural complexity, female status, pacification, suicide, and social stress—are associated with only the first and fourth stages.

The authors of this study integrate recent data with data on ancestral ethnic groups' exposure to the slave trade in order to examine the relationship between this historical exposure and children vaccination status against measles. They find evidence to support their hypothesis that children from mothers whose ancestors belonged to an ethnic group that exported slaves are less likely to be vaccinated against measles, theorizing that this correlation stems from distrust in medical and governmental institutions. Supporting this theory, they also find that groups historically exposed to the slave trade that have higher preference for traditional practices are even less likely to vaccinate their children against measles.