Linking Self‐Determination to Life Outcomes of People With Intellectual and Developmental Disabilities: Criterion Validity of the Self‐Determination Inventory

BACKGROUND: Self-determination has received increasing interest worldwide, both as a key concept in disability policy and as a guiding principle for best practices and lifelong learning. METHOD: The study examined correlations between the Portuguese versions of the Self-Determination Inventory (SDI) and the Self-Determination Scale. A total of 168 participants with and without intellectual and developmental disabilities (IDD) aged 13-60 years (24.7 ± 12.2) completed both instruments. RESULTS: Moderate and significant correlations were found, providing preliminary criterion evidence for the Portuguese translation of the SDI. The main findings include: (1) participants with IDD reported fewer self-determination actions, (2) women scored higher than men and (3) academic qualifications had a limited influence on self-determination scores. CONCLUSIONS: The SDI PT translation is a valid and reliable tool that supports the operationalisation of the construct within the Portuguese context. This study also contributes to a deeper understanding of how self-determination manifests across diverse populations, offering insights into inclusive practices and future theoretical developments.