Validation of a momentary measure of personal expressiveness: Evidence of structural, convergent, discriminant, and known-groups validity

Personal expressiveness (PE) reflects the subjective experience of eudaimonic engagement during activity participation, capturing how strongly activities align with a person's inherent potentials. This study introduces and validates a momentary PE measure for experience sampling research using data from 52 adults (1478 observations). Multilevel confirmatory factor analysis supported a coherent PE factor at both within- and between-person levels, indicating that personal expressiveness reflects a consistent experiential dimension observable both across situations and across people. Convergent validity was evidenced by positive PE–flow associations, while discriminant validity was supported by their distinct two-factor structure and context-varying associations. Known-groups validity emerged through systematic activity differences, with parenting and leisure highest in PE. Findings support the validity of a momentary measure for assessing personal expressiveness as it unfolds across everyday activities and contexts in daily life.