Abstract
Self-concept, which reflects individuals' overarching views of themselves and their qualities, has been implicated in the development of depression. Studying developmental and sex differences in self-concept between middle childhood and mid-adolescence may speak to the processes by which early self-concept contributes to later depression risk; however, such an understanding requires valid assessment tools. We tested the measurement invariance of a widely used behavioral measure of self-concept, the Self-Referent Encoding Task (SRET), across sex and age from middle childhood (age 6) to mid-adolescence (age 15). Participants (n = 546) were assessed longitudinally four times over a 9-year follow-up at ages 6, 9, 12, and 15. The SRET showed measurement invariance, as well as moderate to high stability, across ages 9-15. Using findings of invariance to inform subsequent analyses of developmental differences in youth self-concept, we found that children's negative self-concepts became increasingly negative from ages 9 to 15. Children's positive self-concepts increased from ages 9 to 12 before decreasing to preadolescent levels of positivity from ages 12 to 15. We additionally found measurement invariance of the SRET across sex at ages 9, 12, and 15. No sex invariance was found at age 6. Boys and girls did not differ in positive or negative self-concept at age 9, 12, or 15. We make recommendations for the use of SRET indices in assessing youth self-concept. We also discuss implications for the developmental dynamics of youth self-concept across late childhood and adolescence. (PsycInfo Database Record (c) 2025 APA, all rights reserved).