Incorrect encoding responses improve the classification accuracy of the Word Choice Test

This study investigated whether responses from the Word Choice Test (WCT) encoding trial could provide a supplemental index of performance validity in addition to the traditional Summary score. Participants were 196 adult outpatients who underwent neuropsychological evaluations for various referral reasons related to, but not limited to epilepsy, stroke, and age-related cognitive decline. Participants were classified into valid or invalid performance groups using a criterion-grouping approach based on multiple independent performance validity tests. We derived a supplemental validity indicator, entitled the "Encoding" score, based on the number of correct responses from 43 items on the initial WCT trial, which were identified via critical item analysis. Using cutoffs of ≤40 for the Encoding score and ≤42 for the Summary score together enhanced classification accuracy, yielding an area under the curve of .83. Compared to using the WCT Summary score alone, the combined use of the Encoding and Summary scores increased the sensitivity by .10 to yield a total sensitivity of .58, while maintaining high (.92) specificity. Findings suggest the WCT Encoding score may provide a useful index of performance validity alongside the Summary score. Employing these indicators together can optimize the WCT without adding cost or much time to the evaluation.