Identifying Feigned Cognitive Impairment: Investigating the Utility of Diffusion Model Analyses

Forced-choice performance validity tests are routinely used for the detection of feigned cognitive impairment. The drift diffusion model deconstructs performance into distinct cognitive processes using accuracy and response time measures. It thereby offers a unique approach for gaining insight into examinees’ speed-accuracy trade-offs and the cognitive processes that underlie their performance. The current study is the first to perform such analyses using a well-established forced-choice performance validity test. To achieve this aim, archival data of healthy participants, either simulating cognitive impairment in the Word Memory Test or performing it to the best of their ability, were analyzed using the EZ-diffusion model ( N = 198). The groups differed in the three model parameters, with drift rate emerging as the best predictor of group membership. These findings provide initial evidence for the usefulness of the drift diffusion model in clarifying the cognitive processes underlying feigned cognitive impairment and encourage further research.

Detecting Feigned Cognitive Impairment With Schretlen’s Malingering Scale Vocabulary and Abstraction Test

Schretlen’s Malingering Scale Vocabulary and Abstraction test (MSVA) differs from the majority of performance validity tests in that it focuses on the detection of feigned impairments in semantic knowledge and perceptual reasoning rather than feigned memory problems. We administered the MSVA to children ( n = 41), forensic inpatients with intellectual disability ( n = 25), forensic inpatients with psychiatric symptoms ( n = 57), and three groups of undergraduate students ( n = 30, n = 79, and n = 90, respectively), asking approximately half of each of these samples to feign impairment and the other half to respond genuinely. With cutpoints chosen so as to keep false-positive rates below 10%, detection rates of experimentally feigned cognitive impairment were high in children (90%) and inpatients with intellectual disability (100%), but low in adults without intellectual disability (46%). The rates of significantly below-chance performance were low (4%), except in children (47%) and intellectually disabled inpatients (50%). The reliability of the MSVA was excellent (Cronbach’s α = .93–.97) and the MSVA proved robust against coaching (i.e., informed attempts to evade detection while feigning). We conclude that the MSVA is not ready yet for clinical use, but that it shows sufficient promise to warrant further validation efforts.

A Laboratory Word Memory Test Analogue Differentiates Intentional Feigning from True Responding Using the P300 Event-Related Potential

Symptom exaggeration and feigned cognitive impairment occur commonly in forensic and medicolegal evaluations. As a result, methods to detect feigned cognitive impairment are an indispensable component of neuropsychological assessments. This study reports the results of two neurophysiological experiments using a forced-choice recognition task built from the stimuli of the Word Memory Test and Medical Symptom Validity Test as well as a new linguistically informed stimulus set. Participant volunteers were instructed either to do their best or to feign cognitive impairment consistent with a mild traumatic brain injury while their brain activity was monitored using event-related potentials (ERP). Experiment 1 varied instructions across individuals, whereas Experiment 2 varied instructions within individuals. The target brain component was a positive deflection indicating stimulus recognition that occurs approximately 300 ms after exposure to a stimulus (i.e., the P300). Multimodal comparison (P300 amplitude to behavioral accuracy) allowed the detection of feigned cognitive impairment. Results indicate that, for correct responses, P300s were equivalent for the simulated malingering and good effort conditions. However, for incorrect responses, feigned impairment produced reliable but significantly reduced P300 amplitudes. Although the P300 is an automatic index of recognition—even when knowledge is hidden—its amplitude appears capable of modulation by feigning strategies. Implications of this finding are discussed for research and clinical applications.

Tests of Feigned or Exaggerated Cognitive Impairment

This chapter reviews the most popular and promising instruments for assessing poor effort or feigned cognitive impairment. Referred to as performance validity tests (PVTs), these instruments vary from very brief to quite long and also vary substantially in sophistication and performance. The advantages and disadvantages of each are reported along with the costs of their use (time and money), diagnostic statistics, and recommended cutoff scores. The various PVTs discussed in the chapter are well validated in neurological samples but less so in psychiatric ones. The chapter concludes by noting that although many PVTs are now described as effort tests, there has been no research to accurately measure how much mental effort different tests require.

Measures of Feigned or Exaggerated Incompetence

This chapter describes and reviews the published instruments available to assess feigned incompetence to stand trial. The Inventory of Legal Knowledge has already gained considerable acceptance despite having some significant limitations. The ECST-R Atypical Presentation Scales are included as part of the ECST-R competency assessment instrument and are billed as screening tests for feigned incompetence. However, they address only feigned psychopathology, not feigned cognitive impairment or ignorance of the court system, and are billed as suitable only for screening, not diagnostic, purposes. The strengths and weaknesses of the ILK and the ECST-R are discussed in detail, as are emerging instruments and detection strategies.

A Survey of Competency to Stand Trial Examiners

This chapter reports the results from a nationwide survey of experienced CST examiners regarding their practices, preferences for instruments, and use of collateral data. These examiners also provided estimates of different types of invalid responding (feigned cognitive impairment, amnesia, psychopathology, ignorance of court system, physical infirmity, poor effort) seen in CST defendants. Desirable attributes of CST instruments were assessed, as was the standing of major instruments on each of these attributes. Moderators such as ABPP status, inpatient or outpatient setting, and defense versus prosecution orientation were assessed for their effects on other variables such as instrument choice, use of tests or collateral sources, and estimated rates of invalid responding.