International large-scale assessments aim to measure student competencies reliably across countries and time. However, questions have arisen about how much students’ effort and test-taking motivation affect their performance. Previous research (Butler & Adams, 2007; Penk & Richter, 2017) has shown that in low-stakes assessments, test-taking motivation and effort can affect achievement as strongly as socioeconomic status, making it a critical factor for interpreting trends. The recent decline in PISA scores has raised questions about whether changes in motivation contribute to these patterns. This study addressed two research questions: (1) How has test motivation changed across PISA cycles and by background variables? (2) How has its relationship with mathematics performance evolved? We examined Finnish PISA samples with national questionnaire items from 2015 (N = 5,353), 2018 (N = 4,942), and 2022 (N = 7,216). A latent variable for test motivation was constructed using item response theory. Its relationship with mathematics performance was examined through student-weighted linear regression models, controlling for year, gender, and socioeconomic status. This approach enabled us to assess both temporal changes in motivation and its explanatory power for achievement. Results indicate that test motivation has declined for both boys and girls since 2015. Furthermore, the strength of the association between motivation and mathematics performance has weakened over time. The regression coefficient linking motivation to achievement differed significantly between 2015 and 2022, suggesting that motivation explained a smaller share of performance in the most recent cycle. Finally, we compared predicted score differences across cycles in models with and without motivation included. Accounting for motivation substantially reduced observed declines: the mathematics gap between 2015 and 2018 narrowed from 6.0 to 1.7 points, and the gap between 2015 and 2022 decreased from 26.4 to 17.2 points. These findings highlight two key trends: declining test motivation and a reduced linear dependency between motivation and achievement. By using national extensions to PISA questionnaires, this study offers a novel perspective on student engagement during large-scale assessments and its implications for interpreting performance trends. The results underline the need to consider motivational factors when interpreting international comparisons, and raise questions about how changes in students’ attitudes towards testing may affect the validity of trend estimates. Future research should explore why the link between motivation and achievement is weakening and whether similar patterns occur in other countries.

Butler, J., & Adams, R. J. (2007). The impact of differential investment of student effort on the outcomes of international studies. Journal of Applied Measurement, 8(3), 279–304. Penk, C., & Richter, D. (2017). Change in test-taking motivation and its relationship to test performance in low-stakes assessments. Educational Assessment, Evaluation and Accountability, 29(1), 55–79. https://doi.org/10.1007/s11092-016-9248-7