Development of Shyness in Upper Elementary School Students: A Three-Year Longitudinal Study on the Relationships with Self-Disclosure, Self-Criticism, Internalizing Problems, and Sex Differences

Objectives This study aimed to examine the characteristics of shyness observed during the upper elementary school grades and identify the factors contributing to the persistence of shyness. Additionally, the study investigated whether self-disclosure and self-criticism mediate the relationship between shyness and internalization problems. Methods The study participants comprised 2,327 children who completed three self-reported surveys, from the fourth to the sixth grade. The collected data were analyzed using SPSS Statistics and the PROCESS Macro. A repeated measures ANOVA was conducted to examine developmental characteristics according to age and gender, while a multiple regression model was applied to identify factors influencing shyness. Additionally, a multiple mediation model was employed to assess the significance of the mediating effects. Results First, shyness was found to be more prevalent among female than male students, with a significant increase in sixth grade. However, the interaction effect between sex and age was not significant. Additionally, the proportion of children whose shyness fell within the clinical range (+2 SD) was approximately twice as high from the fifth to the sixth grades compared to the fourth to the fifth grades. Second, self-disclosure was identified as the main predictor of shyness. Self-disclosure in the fourth grade affected shyness and self-disclosure in the upper grades. Third, the individual and sequential mediation pathways of self-disclosure and self-criticism in the relationship between shyness and internalization problems were significant. Conclusions These findings suggest that while shyness tends to increase as children enter adolescence, the risk of it persisting long-term is greater if it exceeds the normal range. Additionally, interventions to improve shyness should focus on self-disclosure. When internalization problems are present, self-disclosure and self-criticism should be considered simultaneously.