Assessment of malingering with simulation designs: threats to external validity

Comprehensive forensic evaluations are predicated on the accurate appraisal of response styles that may affect evaluatees' clinical presentation and experts' conclusions associated with psycholegal issues. In the assessment of malingering, forensic experts often rely heavily on standardized measures that have been validated exclusively via analogue research. While such research augments internal validity, the threats to external validity are readily apparent. As the first study of these threats, type of incentive (positive versus negative), context (a familiar versus unfamiliar scenario), and relevance to the participants was investigated systematically with a between-subjects factorial design. A sample of 231 undergraduates was asked to either (a) feign major depression and given an easily understood description of this disorder or (b) serve as controls responding honestly. They were administered a brief measure of psychopathology (Hopkins Symptom Checklist; Derogatis, Lipman, Rickels, Uhlenhuth, & Covi, 1974) and a recent screen for malingering (Screening Inventory of Malingered Symptoms or SIMS; Smith, 1992) in 1 of 18 experimental conditions. Results suggested that incentive had a main effect on the SIMS. More specifically, simulators under negative incentives appeared more focused in their feigning; they produced more bogus depressed symptoms, but fewer symptoms unrelated to depression. Interactions were also observed between context and incentive, and context and relevance. Implications of these results are explored for both analogue research on malingering and current forensic practice.