Examining the Within- and Between-Person Structure of Callous-Unemotional Traits in Adolescents and Young Adults in Daily Life.

Intensive longitudinal designs have been used to examine the fluctuations of callous-unemotional (CU) traits and their dynamic links with daily correlates; however, scant research has explored how CU traits manifest in daily contexts at the within-person level. This study evaluated the multilevel factor structure and psychometric properties of a short version of the Inventory of CU Traits in daily contexts among adolescents (n = 99, 2,132 daily reports) and young adults (n = 313, 6,431, and 4,018 daily reports at each wave). Both bifactor and correlated-factor models showed acceptable fit and reliability at the within- and between-person levels, though the general factor in the bifactor model demonstrated low reliability in university students. Longitudinal measurement invariance was supported among university students over a 2.5-year period, while structural differences emerged between the two samples. Findings highlight meaningful within-person fluctuations in daily CU traits. Future studies should evaluate the applicability of different factor models for a more accurate assessment across age groups.