Use of the WAIS-III Picture Completion Subtest as an Embedded Measure of Response Bias

In the present study a large sample of credible patients (n = 172) scored significantly higher than a large sample of noncredible participants (n = 195) on several WAIS-III Picture Completion variables: Age Adjusted Scaled Score, raw score, a oRarely Missedo index (the nine items least often missed by credible participants), a oRarely Correcto index (nine items correct 26% of the time in noncredible participants and with at least a 25 percentage-point lower endorsement rate as compared to credible participants), and a oMost Discrepanto index (the six items that were the most discrepant in correct endorsement between groupsat least a 40 percentage point difference). Comparison of the various scores showed that the oMost Discrepanto index outperformed all the others in identifying response bias (nearly 65% sensitivity at 92.8% specificity as compared to at most 59% sensitivity for the other scores). While no differences in Picture Completion scores were observed between less-educated (12 years) and better-educated (epsilon 12 years) credible participants, noncredible participants with 12 years of education scored significantly poorer than noncredible participants with 12 or more years of education. On the oMost Discrepanto index, 76.7% of less-educated noncredible participants were detected as compared to 58.3% of better-educated noncredible participants. Results of the current study suggest that the Picture Completion subtest of the WAIS-III is an effective measure of response bias, and that it may have a unique role in identifying suboptimal effort in less-educated test takers.