Throwing Out the Bathwater but Keeping the Baby: Extending Campbell-Fiske’s Multitrait-Multimethod Framework

2024 marks the 65th anniversary of Campbell and Fiske’s (1959) multitrait-multimethod (MTMM) Guidelines—one of psychology’s most influential frameworks for evaluating construct validity. Yet retirement plans are premature. Although structural equation modeling (SEM)-based MTMM models have advanced the field, their application often faces convergence difficulties, compromises trait-method symmetry, and lacks consensus regarding optimal modeling strategies, creating ongoing barriers for applied researchers.Building on a latent correlation matrix derived from a well-fitting measurement model with multiple indicators, our Extended Guidelines address key criticisms typically raised against manifest correlations and offer rich, formative insights not easily captured by SEM-based approaches. We present an Extended Campbell-Fiske framework treating MTMM structures as two-facet designs, with traits and methods considered symmetrically and substantively important—complementing SEM approaches and providing a flexible, accessible tool for construct validation.We illustrate this approach using complex data from a two-facet design (N = 18,047 eighth graders across four countries), crossing five trait constructs and five domains. Employing asymptotic parameter comparisons, we demonstrate the Extended Guidelines’ utility to:•Provide summary statistics, standard errors, and statistical significance tests for each Campbell-Fiske validity criterion,•Evaluate convergent and discriminant validity across traits, methods, and interactions,•Examine facet-specific and interaction patterns in construct validity, and•Test generalizability across populations, settings, or measurement conditions.Our findings reinforce the enduring relevance of the Campbell-Fiske framework while offering a modern, broadly applicable tool for construct validation across diverse MTMM designs.