What is the best model of grit among junior high students: Model selection, measurement invariance, and group difference

Grit is a non-cognitive construct based on personality theory that fosters individuals to perform better and achieve their goals. Previous researchers validated the psychometric properties of grit for adults and older adolescents but ignored that for early adolescents. An inappropriate measurement model may mislead researchers and teachers to misapprehend grit measures. This study aimed to identify the most appropriate grit model for early adolescents. Three factorial models (i.e., two-factor, one-factor, and bi-factor models) were evaluated and compared. Subsequently, we tested the measurement invariance (MI) and mean differences of grit across grade and gender groups. Participants were 672 junior high students (51% boys, aged 12–15) in Taiwan. The results showed that the two-factor model was the best grit model. This finding revealed that adolescents tend to comprehend grit with two distinct concepts, consistency in interest (CI) and perseverance of effort (PE), instead of a single compound. In addition, the results showed that the two-factor model retained strong invariance for grade and gender, justifying the comparison of grit scores over grade and gender groups for junior high students. Moreover, we did not find any group difference in the facets of grit by gender and grades. This result showed that grit is a stable personality for junior high students. The relationships between grit constructs and criteria, such as conscientiousness and academic achievements, were tested and discussed.