Supplementary file 1_The influence of children’s theory of mind and sibling relationship quality on sibling teaching in the Chinese family with two children.docx

IntroductionSibling teaching provides an important context for children’s cognitive and social development, particularly in families with more than one child. Within the Chinese family context shaped by the two-child policy, older siblings often assume instructional roles. However, limited research has examined how children’s theory of mind and sibling relationship quality jointly influence instructional behaviors and learning engagement during sibling teaching interactions. This study aimed to address this gap by examining these associations across different instructional task types.
MethodsThirty-four sibling dyads from Chinese two-child families participated in structured teaching tasks, including mathematical/spatial and language activities. Firstborn children (aged 6–12 years) acted as instructors, while second-born children (aged 3–6 years) acted as learners. Children’s theory of mind was assessed using standardized tasks, and sibling relationship quality was reported by parents. Teaching and learning behaviors were coded from video-recorded interactions using an established observational coding system. Multiple regression analyses were conducted to examine predictive relationships.
ResultsResults showed that instructors’ theory of mind positively predicted the use of cognitive strategies and positive feedback across both mathematical/spatial and language teaching tasks. Learners’ Theory of Mind was negatively associated with off-task behavior in both task types and with refusal behavior in language teaching tasks. Sibling relationship quality positively predicted instructors’ cognitive strategies and learners’ verbal and physical engagement, with stronger effects observed in mathematical/spatial teaching tasks.
DiscussionThese findings highlight the joint roles of social–cognitive development and sibling relationship quality in shaping sibling teaching interactions. By distinguishing between task types and examining both instructor and learner behaviors, the study extends existing theories of sibling teaching and underscores the importance of family-based learning processes within a Chinese cultural context.