Abstract
Malingering is defined as the intentional false presentation of symptoms driven by an external incentive, which can be financial (e.g., compensation), legal (e.g., diminished criminal responsibility), or for other types of personal gain (e.g., to obtain medication). Malingering occurs on a non-trivial scale in both civil and criminal contexts, and causes serious legal and social consequences. The aim of this thesis was to examine whether a multi-method assessment of symptoms might enhance the detection of malingering, and whether an assessor’s cultural background impacted their perceptions of malingering.In this thesis, three different methods for detecting malingering were tested across a total of eight studies. Specifically, we tested a novel lie-detection tool, the Verifiability Approach (VA) in order to investigate whether the VA could contribute to the credibility assessment of physical symptom reports. The logic behind the VA is that people who are telling the truth should produce more verifiable details - information that can, in principle, be checked – compared to liars. Liars, in contrast, tend to avoid verifiable information and report non-verifiable details instead. Next, we critically examined the utility of a controversial task, the Modified Stroop task (MST), a reaction time measure of attentional bias among patients, in detection of malingering. The MST is comprised of disorder-related and neutral words presented in different colors. The task is to color-name the words while disregarding their semantic meaning. The idea behind the MST is that genuine patients should show prolonged reaction time (RT) when presented with disorder-related, compared to neutral, words (i.e., the MST effect). We also applied a newly developed measure of over-reporting, the Self-Report Symptom Inventory (SRSI), in order to investigate symptom endorsement among malingerers. The SRSI includes two scales of symptoms: genuine (plausible) symptoms and pseudosymptoms (unlikely complaints). The rationale behind the SRSI is that genuine patients will endorse more of genuine and fewer of the pseudosymptoms, while malingerers will overendorse both types of symptoms. Finally, we investigated whether the cross-cultural background of practitioners influenced their view of exaggerated symptoms.
In the first experimental chapter (Chapter 2), we report the findings of research designed to test the VA with respect to the detection of fabricated symptom statements. We investigated the extent to which people with genuine symptoms compared to malingerers differed in the provision of checkable details. In Study 1, we examined statements of students genuinely suffering from various physical symptoms (e.g., headache, backpain), and students instructed to malinger such experiences. We found that malingerers, compared to truth tellers, produced longer statements that contained fewer verifiable details. In Study 2, we repeated the task, but participants were informed that their statements would be inspected for verifiable information. Providing this additional information to participants led to non-significant differences between malingerers and truth tellers in terms of both verifiable and non-verifiable information, and the overall length of statements. In Study 3, we experimentally induced symptoms (physical exercise) in one group of students (truth tellers), while two other groups received instructions to malinger having been engaged in physical exercise. Participants were not informed about the type of information they should provide. The results confirmed our findings from Study 1. We observed longer statements containing more non-verifiable information for both malingering groups (cf. control group). In other words, an extensive amount of non-verifiable details was indicative of fabricated symptom reports in both Study 1 and Study 3.
In Chapter 3, we tested whether a reaction time task, the MST, used in combination with the SRSI, might assist in the detection of fabricated anxiety-related symptoms. In Study 4, we focused on test-anxiety using a within-subject design. Students who were not suffering from test anxiety were asked to first genuinely respond to the MST task and the SRSI, and seven days later they were instructed to feign having test-anxiety and to repeat the tasks. We found that students in the latter session produced the MST effect typically found in genuine test-anxiety patients, while the MST effect did not emerge in the first session. Participants in the second session overendorsed genuine symptoms and pseudosymptoms related to anxiety, compared with the first session, which led to the detection rate of 77% of test anxiety malingerers. In Study 5, we investigated PTSD-related symptoms, and included three groups of participants: 1) participants with current high impact aversive experiences, 2) participants with low impact aversive experiences, and 3) actors, who also had a low impact history but were asked to simulate being under the effects of a high impact of aversive experience. The MST effect did not emerge in any of the groups, however, the actors produced longer response latencies than both high and low impact groups. Actors also overendorsed items of the SRSI, thus 89% of these malingerers were successfully detected as such. Problematically, however, 27% of the honest group were also classified as malingerers.
In Chapter 4, we focused on the SRSI alone, and its utility for detecting fabricated physical (pain-related) and psychological (anxiety-related) symptoms (Study 6). In a between subjects design we included an honest comparison group and two groups of simulators (pain and anxiety symptoms). The simulators of pain and simulators of anxiety endorsed more genuine symptoms and pseudosymptoms than participants in the honest group. Also, both simulators groups over-endorsed symptoms corresponding to their alleged conditions. The detection rates reached 48% for simulators of pain, and 74% for simulators of anxiety, suggesting that the SRSI has a low sensitivity to simulated physical complaints.
In Chapter 5 (Study 7), using a combination of the VA and SRSI, we wanted to examine malingerers’ strategies in fabricating exposure narratives and symptom reports in a PTSD-related condition. In a between subjects design, the honest comparison group was experimentally induced with PTSD-like symptoms, using a Virtual Reality (VR) paradigm. The other group was not exposed to the VR, but was instructed to simulate that experience (malingerers). We applied the VA to examine the veracity of their exposure narratives, and our findings were consistent with the general results reported in Chapter 2. Malingerers produced longer statements containing more non-verifiable details, while the honest group included a higher proportion of verifiable information. The quality of the symptom reports was investigated using the subscales of the SRSI describing genuine and pseudosymptoms pertaining to anxiety and PTSD complaints. Malingerers endorsed more of both genuine symptoms and pseudosymptoms than honest group.
Finally, in Chapter 6 (Study 8), we investigated the influence of the cultural background of practitioners on their plausibility judgments concerning various symptoms. We included Western and non-Western practitioners, and presented them with a mix of atypical symptoms, dissociative symptoms, and every-day complaints. Their task was to rate the plausibility of each symptom from exaggerated to authentic. There were no significant differences between culturally diverse practitioners in their plausibility judgments. All practitioners rated atypical and dissociative items as significantly less authentic than every-day complaints, but they did not distinguish between atypical symptoms and dissociative symptoms.
In sum, our results indicated that, with certain adjustments, the VA might contribute to symptom validity assessment. The MST, however, was shown to be an unreliable detection tool, the use of which should be avoided to detect symptom fabrication. The SRSI appears to be a promising method for detecting symptom over-reporting. Further research is necessary to establish the generalizability of our findings to different samples, such as patients.
| Date of Award | May 2018 |
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| Original language | English |
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| Supervisor | Lorraine Hope (Supervisor), James Ost (Supervisor), Harald Merckelbach (Supervisor) & Marko Jelicic (Supervisor) |