ABSTRACT
BACKGROUND: A new measure of self-determination, the Self-Determination Inventory: Student Report (Spanish version), has recently been adapted and empirically validated in Spanish language. As it is the first instrument intended to measure self-determination in youth with and without disabilities, there is a need to further explore and strengthen its psychometric analysis based on item response patterns. METHOD: Through item response theory approach, this study examined item observed distributions across the essential characteristics of self-determination. RESULTS: The results demonstrated satisfactory to excellent item functioning patterns across characteristics, particularly within agentic action domains. Increased variability across items was also found within action-control beliefs dimensions, specifically within the self-realisation subdomain. CONCLUSIONS: These findings further support the instrument's psychometric properties and outline future research directions.
