Inhibition/switching is not necessarily harder than inhibition: an analysis of the D-KEFS color-word interference test

Abstract

The Delis-Kaplan Executive Function System (D-KEFS) Color-Word Interference Test (CWIT) was designed to improve upon the Stroop task by including an inhibition/switching trial, which was designed to be more difficult than the inhibition trial in terms of time to completion and number of errors. The D-KEFS standardization data support this view. However, in clinical practice, we have noticed that many people perform better on the inhibition/switching trial than the inhibition trial. We examined the prevalence and correlates of this atypical performance pattern on the CWIT. Patients seeking outpatient neuropsychological evaluation (n = 119) completed the CWIT as part of a larger test battery. About 57.1% of patients demonstrated an atypical pattern of performance for either completion time or errors. Patients with an atypical pattern for completion time were significantly slower at color naming and word reading than patients with a typical pattern. Patients with an atypical pattern for errors performed better on measures of learning and semantic verbal fluency than patients with a typical pattern. A majority of patients in our sample exhibited atypical performance on the CWIT, and some preliminary correlates of this pattern might aid clinical interpretation.