Self-Concept in Adolescent Twins: A Czech Study on Zygosity and Normative Comparison

Abstract Self-concept in adolescence plays a key role in psychological adjustment, yet its development in twins remains underexplored — especially in Central Europe. While previous studies suggest minor differences between monozygotic (MZ) and dizygotic (DZ) twins, cultural and contextual influences may affect how twins perceive themselves. This mixed-method study examined 336 Czech adolescent twins (168 twin pairs; 32 MZ, 136 DZ) aged 11–15 years. Participants completed three standardized instruments: the Behavioral and Psychological Adjustment Questionnaire (BPQA), the School Performance and Adjustment Scale (SPAS), and the Rosenberg Self-Esteem Scale (RSES). Quantitative analyses included t tests, Analyses of Variance (ANOVAs), and Pearson correlations. To triangulate findings, focus group interviews were conducted with three twin pairs and analyzed thematically. No statistically significant differences were found between MZ and DZ twins across BPQA, SPAS, and RSES measures. However, small, nonsignificant trends suggested slightly higher emotional self-concept scores in MZ twins. A modest gender difference emerged: girls reported more internalizing symptoms. Correlational analysis showed that lower behavioral difficulties were associated with higher school adjustment and self-esteem. Thematic analysis from focus groups confirmed key patterns such as the emotional safety of twinship and the struggle for individuality. Zygosity does not appear to be a major predictor of self-concept in early adolescence. Instead, self-perception in twins is shaped by a complex interplay of mental health, family dynamics, and peer context. Future research should compare twin self-concept development across cultures to further examine sociocultural influences.