Ability of malingering measures to differentiate simulated versus genuine mental retardation

Melanie R Farkas, Fordham University

Abstract

Following the ban on capital punishment for offenders with mental retardation (Atkins v. Virginia, 2002), forensic clinicians have increasingly faced referral questions involving possible mental retardation. Despite the substantial proportion of persons with mental retardation in the criminal justice system, few studies examine the accuracy of malingering detection measures among respondents with genuine mental retardation. This investigation evaluated the ability of the Dot Counting Test (DCT), Test of Memory Malingering (TOMM), and Structured Interview of Reported Symptoms (SIRS) to distinguish 43 honestly responding individuals previously diagnosed with mild mental retardation from 43 normal-intellect individuals who feigned intellectual deficits. ^ Malingering measure scores were uncorrelated with each other and with estimated IQ scores. Slowed processing in respondents with mental retardation affected the DCT's accuracy, as it did not improve upon chance in discriminating between groups across its range of cutoff scores and achieved high sensitivity but poor specificity. The SIRS was more accurate across cutoff scores and achieved high sensitivity, but an unacceptably high proportion of participants with mental retardation failed the recommended total score cutoff, likely because presence of psychiatric comorbidity was associated with increased scores. The TOMM was most accurate both overall and using its recommended cutoff score. A model including the TOMM and SIRS generated more accurate classifications than any single measure, correctly classifying almost all persons with mental retardation. Optimal cutoff scores that maximized specificity substantially decreased sensitivity for the DCT and SIRS but only moderately compromised the TOMM's sensitivity. ^ The TOMM thus shows promise for use in Atkins evaluations, while clinicians cannot have confidence that respondents who fail the DCT are malingering. The SIRS provides unique information about response set, but clinicians must use caution when other evidence suggests both psychiatric illness and mental retardation may be present. Future research with a more variable sample including suspected real-world malingerers should seek identifiable response patterns in persons who feign mental retardation versus those who feign psychiatric illness, should evaluate the effect of coaching malingerers on the strengths and limitations of mental retardation, and should explore measures that share characteristics of the TOMM and SIRS. ^

Subject Area

Psychology, Clinical|Psychology, Psychometrics

Recommended Citation

Melanie R Farkas, "Ability of malingering measures to differentiate simulated versus genuine mental retardation" (January 1, 2008). ETD Collection for Fordham University. Paper AAI3337629.
http://fordham.bepress.com/dissertations/AAI3337629

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