We conducted preregistered replications of 28 classic and contemporary published findings, with protocols that were peer reviewed in advance, to examine variation in effect magnitudes across samples and settings. Each protocol was administered to approximately half of 125 samples that comprised 15,305 participants from 36 countries and territories. Using the conventional criterion of statistical significance (p < .05), we found that 15 (54%) of the replications provided evidence of a statistically significant effect in the same direction as the original finding. With a strict significance criterion (p < .0001), 14 (50%) of the replications still provided such evidence, a reflection of the extremely high-powered design. Seven (25%) of the replications yielded effect sizes larger than the original ones, and 21 (75%) yielded effect sizes smaller than the original ones. The median comparable Cohen’s ds were 0.60 for the original findings and 0.15 for the replications. The effect sizes were small (< 0.20) in 16 of the replications (57%), and 9 effects (32%) were in the direction opposite the direction of the original effect. Across settings, the Q statistic indicated significant heterogeneity in 11 (39%) of the replication effects, and most of those were among the findings with the largest overall effect sizes; only 1 effect that was near zero in the aggregate showed significant heterogeneity according to this measure. Only 1 effect had a tau value greater than .20, an indication of moderate heterogeneity. Eight others had tau values near or slightly above .10, an indication of slight heterogeneity. Moderation tests indicated that very little heterogeneity was attributable to the order in which the tasks were performed or whether the tasks were administered in lab versus online. Exploratory comparisons revealed little heterogeneity between Western, educated, industrialized, rich, and democratic (WEIRD) cultures and less WEIRD cultures (i.e., cultures with relatively high and low WEIRDness scores, respectively). Cumulatively, variability in the observed effect sizes was attributable more to the effect being studied than to the sample or setting in which it was studied.

Significance: What explains the striking regional differences in COVID-19 severity around the world? We reveal the role of culture in mask usage, a precautionary measure vital for mitigating the pandemic. Leveraging a dataset of all 3,141 counties of the 50 US states, a dataset of 16,737 individuals in the 50 US states, a dataset of 367,109 individuals in 29 countries, and a dataset of 277,219 Facebook users in 67 countries, we provide evidence that people in more collectivistic (versus individualistic) regions are more likely to wear masks. Our research suggests that culture fundamentally shapes how people respond to crises like the COVID-19 pandemic.

Data recently published in PNAS mapped out regional differences in the tightness of social norms across China [R. Y. J. Chua, K. G. Huang, M. Jin, Proc. Natl. Acad. Sci. U.S.A. 116, 6720–6725 (2019)]. Norms were tighter in developed, urbanized areas and weaker in rural areas. We tested whether historical paddy rice farming has left a legacy on social norms in modern China. Premodern rice farming could plausibly create strong social norms because paddy rice relied on irrigation networks. Rice farmers coordinated their water use and kept track of each person’s labor contributions. Rice villages also established strong norms of reciprocity to cope with labor demands that were twice as high as dryland crops like wheat. In line with this theory, China’s historically rice-farming areas had tighter social norms than wheat-farming areas, even beyond differences in development and urbanization. Rice–wheat differences were just as large among people in 10 neighboring provinces (n = 3,835) along the rice–wheat border. These neighboring provinces differ sharply in rice and wheat, but little in latitude, temperature, and other potential confounding variables. Outside of China, rice farming predicted norm tightness in 32 countries around the world. Finally, people in rice-farming areas scored lower on innovative thinking, which tends to be lower in societies with tight norms. This natural test case within China might explain why East Asia—historically reliant on rice farming—has tighter social norms than the wheat-farming West. Significance Rice is a highly interdependent crop. Rice required far more labor than dryland crops like wheat, and rice’s irrigation networks forced farmers to coordinate water use. To deal with these demands, rice villages developed strong norms for labor exchange. Using China as a natural test case, we compare nearby provinces that differ in rice and wheat, but share the same ethnicity, religion, and national government. In survey data from over 11,000 Chinese citizens, rice-farming provinces report tighter norms than traditionally wheat-growing provinces. Rice also predicts tight norms around the world. These data suggest that China’s agricultural past still shapes cultural differences in the modern day—and perhaps explain why East Asia has tighter social norms than the wheat-growing West.

In the early days of the coronavirus outbreak, we observed mask use in public among 1,330 people across China. People in regions with a history of farming rice wore masks more often than people in wheat regions. Cultural differences persisted after taking into account objective risk factors such as local COVID cases. The differences fit with the emerging theory that rice farming's labor and irrigation demands made societies more interdependent, with tighter social norms. Cultural differences were strongest in the ambiguous, early days of the pandemic, then shrank as masks became nearly universal (94%). Separate survey and internet search data replicated this pattern. Although strong cultural differences lasted only a few days, research suggests that acting just a few days earlier can reduce deaths substantially.

Although cross-cultural research suggests that the development and functionality of secondary coping strategies are substantially influenced by the broader cultural context, research findings are not completely conclusive. Some studies indicate that secondary coping is more adaptive for Asian participants compared with Westerners, while others emphasize the adaptability of the coping style in Asian, but not Western, contexts. The main objective of the present study was to systematically test for ethnic and contextual differences in the effectiveness of secondary strategies (measured in the form of acceptance and positive reinterpretation) in reducing the negative effects of acculturative stress on somatic symptoms with samples of international students. A 3-month longitudinal study was conducted in two different contexts: (a) Asian and Western international students in China (Asians: n = 53, Westerners: n = 51) and (b) similar groups in New Zealand (Asians: n = 61, Westerners: n = 65). The data were subjected to a hierarchical regression analysis with changes in psychological symptoms functioning as the dependent variable. Findings indicated that stress, secondary coping, and cultural context significantly interacted in predicting changes in somatic symptoms. Specifically, secondary coping exacerbated the negative effects of acculturative stress on psychological adjustment in New Zealand. In contrast, secondary coping functioned as a buffer in China, such that it was effective at reducing the negative impact of stress over time. Findings indicated that ethnicity did not significantly moderate the stress–coping–adjustment relationship. Our results show that the effectiveness of secondary coping varies as a function of the cultural context.