Why the Big Five Personality Traits Are Composites, not Common Causes: Implications for Measurement, Prediction, and Causal Inference

The Big Five personality traits are often treated as common causes of the Big Five items in reflective measurement models such as factor analysis models and item response theory models. For example, extraversion items are modeled as reflective indicators influenced by the latent variable extraversion (i.e., the common cause). However, the Big Five do not correspond to five biological, environmental, or mental entities that could serve as common causes. The notion that the Big Five are common causes is furthermore challenged by direct causal effects, semantic overlap, and logical connections among the Big Five items. Despite these concerns, researchers continue to use methods and theories that implicitly or explicitly assume that the Big Five are common causes. I argue for three shifts: (a) Ontological shift: The Big Five are best understood as composites of personality items—not as real entities that cause item responses. (b) Methodological shift: For descriptive and predictive research, the composite-formative measurement model offers a more appropriate modeling approach than the reflective measurement model, with item retest reliabilities replacing Cronbach's alpha or McDonald's omega for reliability estimation. (c) Conceptual shift: For researchers interested in causal inference—which is essential for building theories and designing interventions—I recommend moving beyond the Big Five toward narrower personality traits grounded in clear theoretical conceptualizations and assessed multi-modally (e.g., self-reported talkativeness, other-reported talkativeness, audio recordings).