Multidimensional Item Response Theory of the BIS/BAS Scales: Evidence for a Bifactor Model Structure

Carver and White’s Behavioral Inhibition/Behavioral Activation System Scales (BIS/BAS Scales) is the most commonly used measure of the behavioral inhibition/activation systems. However, the original four-factor model often required scale modifications to reach adequate model fits in other samples. Alternate factor structures have also been proposed. The current study examined competing factor solutions using multidimensional item response theory. Participants included 2,186 college students in a large, diverse university. Results indicate that the bifactor model performed significantly better than alternatives and demonstrated adequate model fit. Analyses of ω reliability, construct replicability, percent of uncontaminated correlations, and average relative parameter bias provide additional evidence that the use of bifactor model over a unidimensional or multidimensional, single-level structure is appropriate. Item discrimination and difficulty parameters identified areas of future development. The present findings suggest that the BIS/BAS Scales should be conceptualized as a bifactor structure including a BIS factor and a general BAS factor with three BAS specific subfactors (Drive, Fun Seeking, Reward Responsiveness). Additional refinement of the BAS subconstructs is necessary if they are planned for use.