Unreliable Block Span Reveals Simulated Intellectual Disability on the Stanford-Binet Intelligence Scales-Fifth Edition

Previously developed validity measures are largely lacking in their ability to accurately distinguish malingerers from individuals with genuine intellectual disabilities (ID). The purpose of the present study was to develop a validity index for the Stanford-Binet Intelligence Scales-Fifth Edition (SB-5) aimed at detecting malingered ID. Fifty-four college students were instructed to feign impairment consistent with mental retardation while completing the SB-5. Simulated malingerers performed significantly poorer on the Block Span task of the SB-5 than did individuals with genuine impairment. A Block Span Validity Index (BSVI) cutoff score of less than 10 showed perfect specificity by correctly identifying all persons with true ID and demonstrated 52% sensitivity in identifying persons feigning impairment. For the detection of malingered ID, the BSVI yielded favorable results, although more research is needed to validate the BSVI using a known-groups study design.