Abstract
BACKGROUND: Social motivation plays a key role in sports participation but is underexplored in measurement tools. The Social Motivational Orientations in Sport Scale (SMOSS) is the only instrument assessing these orientations; however, no Spanish version exists for children. The primary objective of this study was to culturally adapt and psychometrically validate a Spanish version of the SMOSS for children aged 6-12 years. METHODS: The SMOSS for children (SMOSS-C) was translated and culturally adapted. Comprehension was evaluated through cognitive interviews, and reliability was assessed via test-retest with 128 Spanish schoolchildren. Analyses included confirmatory factor analysis (CFA), Cronbach's alpha (α), and intraclass correlation coefficient (ICC). RESULTS: CFA confirmed the three-factor structure (affiliation, recognition, status) with excellent fit indices (χ (2)/df = 1.667, RMSEA =.072, CFI =.943, TLI =.926). Internal consistency ranged from questionable to good (α = .636-.891), except for items 6 and 15 (poor/unacceptable). Temporal stability was moderate to near-perfect (ICC =.467-.891), with items 6 and 15 showing only fair agreement. Measurement error was low for the total score (SEM% = 7.0; MDC% = 19.5), indicating good accuracy. CONCLUSIONS: The SMOSS-C shows a valid factorial structure, acceptable internal consistency, and good temporal reliability for most items and the overall score. Despite two weaker items, it is a reliable tool for assessing social motivational orientations in sport among Spanish schoolchildren. It enhances understanding of social influences on motivation for physical activity and informs pedagogical strategies. As part of the social domain, the SMOSS-C supports the Spanish Physical Literacy Assessment for Children (SPLA-C) model, the first physical literacy assessment instrument in Spain.