Assessing the SciPop Scale across 68 Countries/Regions: Testing Measurement Invariance and Alignment in Science-Related Populist Attitudes

Science-related populism, as a specific form of populist attitude toward scientific authority, has attracted increasing scholarly attention in recent years. Although the SciPop Scale has been proposed to measure this attitude, its cross-national validity and measurement invariance remain underexplored. Moreover, the impact of scoring approaches corresponding to different measurement philosophies on the interpretation of the SciPop Scale has not yet been examined. Using data from the “Trust in Science and Science-Related Populism” (TISP) project and the Swiss Science Barometer, this study analyzes a sample of 69,341 participants across 68 countries and regions, as well as a nationally representative Swiss sample of 1124 participants, to examine the psychometric properties of the SciPop Scale. The results indicate that: first, the SciPop Scale demonstrates high reliability, with a four-factor structure being the most widely applicable optimal model; second, full measurement invariance is achieved across sex, age, education, residence, political orientation, and religiosity, while partial invariance is observed across geographic regions, economic development levels, cultural values, and political regimes. However, overall cross-national comparability remains limited, though approximate invariance can be attained through measurement alignment. Third, different scoring methods yield inconsistent identification of the weakest dimension. Fourth, when examining criterion validity, alignment-adjusted scores based on the Bollen approach consistently outperform those based on the Goertz approach, showing greater explanatory power for cross-national or cross-group comparisons. Taken together, this study not only provides evidence for cross-national applicability of the SciPop Scale but also engages with broader questions regarding the measurement philosophy of populist attitudes. The choice of scoring method is not merely a technical decision; it directly shapes how the structure of populism is understood and interpreted.