Structural validity and measurement invariance of the Brief Positive and Negative Affect Scale in emerging adulthood across countries and between women and men

Introduction: Emerging adulthood (ages 18–29) is a key period of emotional and social development, and cross-cultural research is essential to understanding how these processes manifest in diverse Latin American contexts. Given the need for brief, culturally valid tools to assess affect during this stage, this study focuses on the validation of the 10-item Positive and Negative Affect Scale in emerging adults from Chile and Ecuador and evaluate its measurement invariance across country and sex groups. Methods: A psychometric cross-sectional design was used to assess a sample of 1693 emerging adults (61.7% women) aged 18-29 years (M = 21.94, SD = 2.81). The sample included 983 participants from Chile (M = 22.52, SD = 2.57) and 710 from Ecuador (M = 21.13, SD = 2.94). Results: The results indicate that the Positive and Negative Affect Scale demonstrates adequate structural validity in both countries and both sexes. Strict invariance was achieved across Chile and Ecuador, as well as by sex, supporting the comparability of scores across groups. Regarding latent means, Chilean participants reported lower levels of both positive and negative affect compared to their Ecuadorian counterparts. Additionally, men reported higher levels of positive affect, whereas women reported higher levels of negative affect. Conclusions: The findings are consistent with theoretical models of subjective well-being that conceptualize positive and negative affect as related but distinct dimensions. Although the results cannot be directly generalized to clinical or public health settings, they suggest that the Brief Positive and Negative Affect Scale may serve as a brief tool for assessing affect in both research and applied contexts, including initial screening and large-scale assessments. However, the use of non-probabilistic sampling may limit generalizability, and future studies should include more diverse populations and longitudinal designs to further examine the robustness of these findings.