Criterion validity of low intelligence scale of the Sims

Abstract

Objective: The Structured Inventory of Malingered Symptomatology (SIMS) is a widely used test. We evaluated the criterion validity of SIMS Low Intelligence scale (LI). Our previous study showed that the LI scale consists only of arithmetic tasks, logical tasks and tasks evaluating general knowledge and no tasks assessing non-verbal intelligence. None of these tasks appeared suited to differentiate malingerers from patients with cognitive impairment such as impairments documented in survivors of high impact car accidents. Method: We used ANOVA to compare SIMS LI scores from four samples: 23 survivors of high impact motor vehicle accidents (MVA), Capilla Ramírez‘s data of 30 persons instructed to malinger whiplash symptoms, Parks’s data of 26 undergraduates instructed to feign post-concussive symptoms and data of 34 normal controls published in SIMS manual. Results: In the ANOVA, LI scores of the 23 injured survivors of high impact MVAs were significantly higher than scores of 30 malingerers of whiplash and of normal controls, but they were not significantly different from Parks’s malingerers of post-concussive symptoms, i.e., from malingerers of cognitive impairment. Conclusions: Patients with intense post-concussive symptoms are likely to obtain LI score levels similar to persons instructed to malinger post-concussive symptoms. Both the legitimately injured patients and the malingerers of post-concussive symptoms are likely to score higher on the LI scale than normal controls. This is further evidence that the SIMS and its scales constitute a pseudo psychological test without capacity to differentiate malingerers from legitimate patients.