Executive functioning in psychogeriatric patients: scalability and construct validity of the Behavioral Dyscontrol Scale (BDS)

OBJECTIVES: Item response theory was used to test the scalability of the Behavioral Dyscontrol Scale (BDS). The BDS assesses the control of voluntary movement, working memory and self-monitoring. Construct validity of the BDS was examined with confirmatory factor analysis. METHODS: The BDS was administered to 693 consecutive, community-dwelling visitors of a psychogeriatric day unit (424 women and 269 men between the ages of 50 and 94). Unidimensionality of the BDS was determined using Mokken's scalogram analysis. The BDS total score was correlated with other measures of executive function (Expanded Mental Control Test, category fluency, and alternating graphical sequences) and with episodic memory tests of orientation and delayed picture recognition in order to test a model of distinct latent constructs of executive functioning and episodic memory. RESULTS: Loevinger's scalability coefficient H was 0.58 for the complete item set of the BDS. Subjects can be ordered on the latent dimension of executive ability. The first eight items of the BDS (deleting the insight rating) satisfy the assumption of non-intersecting item characteristic curves (double monotonicity) which means that they comprise a Guttman-ordered scale (H = 0.60). The BDS and three independent measures of executive control strongly correlated with a latent construct of executive functioning (convergent validity). However, discriminant relations with a nonexecutive construct (recognition memory and orientation) could not be demonstrated. CONCLUSIONS: The BDS satisfies criteria for scalability according to item response theory. Its construct validity as an executive-specific measure is as yet unclear.