International stability and change in explicit and implicit attitudes: An investigation spanning 33 countries, five social groups, and 11 years (2009–2019)

Whether and when explicit (self-reported) and implicit (automatically revealed) social group attitudes can change has been a central topic of psychological inquiry over the past decades. Here, we take a novel approach to answering these longstanding questions by leveraging data collected via the Project Implicit International websites from 1.4 million participants across 33 countries, five social group targets (age, body weight, sexuality, skin tone, and race), and 11 years (2009–2019). Bayesian time-series modeling using Integrated Nested Laplace Approximation revealed changes toward less bias in all five explicit attitudes, ranging from a decrease of 18% for body weight to 43% for sexuality. By contrast, implicit attitudes showed more variation in trends: Implicit sexuality attitudes decreased by 36%; implicit race, age, and body weight attitudes remained stable; and implicit skin tone attitudes showed a curvilinear effect, first decreasing and then increasing in bias, with a 20% increase overall. These results suggest that cultural-level explicit attitude change is best explained by domain-general mechanisms (e.g., the adoption of egalitarian norms), whereas implicit attitude change is best explained by mechanisms specific to each social group target. Finally, exploratory analyses involving ecological correlates of change (e.g., population density and temperature) identified consistent patterns for all explicit attitudes, thus underscoring the domain-general nature of underlying mechanisms. Implicit attitudes again showed more variation, with body-related (age and body weight) and sociodemographic (sexuality, race, and skin tone) targets exhibiting opposite patterns. These insights facilitate novel theorizing about processes and mechanisms of cultural-level change in social group attitudes. Public Significance Statement How did explicit (self-reported) and implicit (automatic) attitudes toward five social categories (age, body weight, sexuality, skin tone, and race) change across 33 countries between 2009 and 2019? Harnessing advances in statistical techniques and the availability of large-scale international data sets, we show that all five explicit attitudes became less negative toward stigmatized groups. Implicit attitudes showed more variation by target: Implicit sexuality attitudes also decreased in bias, but implicit age, body weight, and race attitudes did not change, and implicit skin tone attitudes even increased in bias favoring light-skinned over dark-skinned people. These findings underscore the possibility of widespread changes in a direction of more positivity toward stigmatized social groups, even at an automatic level. However, increasing bias in certain domains suggests that these changes are far from inevitable. As such, more research will be needed to understand how and why social group attitudes change at the cultural level.