Multidimensional Modeling of Traits and Response Styles

Response styles can influence item responses in addition to a respondent’s latent trait level. A common concern is that comparisons between individuals based on sum scores may be rendered invalid by response style effects. This paper investigates a multidimensional approach to modeling traits and response styles simultaneously. Models incorporating different response styles as well as personality traits (Big Five facets) were compared regarding model fit. Relationships between traits and response styles were investigated and different approaches to modeling extreme response style (ERS) were compared regarding their effects on trait estimates. All multidimensional models showed a better fit than the unidimensional models, indicating that response styles influenced item responses with ERS showing the largest incremental variance explanation. ERS and midpoint response style were mainly trait-independent whereas acquiescence and disacquiescence were strongly related to several personality traits. Expected a posteriori estimates of participants’ trait levels did not differ substantially between two-dimensional and unidimensional models when a set of heterogeneous items was used to model ERS. A minor adjustment of trait estimates occurred when the same items were used to model ERS and the trait, though the ERS dimension in this approach only reflected scale-specific ERS, rather than a general ERS tendency.