Deception and Deception Detection of Feigned Trauma Symptoms

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Devilly, Grant J.

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Kebbell, Mark R.

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Through this research project we assessed the ability of psychology students to enact and detect deception enacted through feigning symptoms of Post Traumatic Stress Disorder (PTSD). Psychometric and psychophysiological testing are often used to assess the feigning or malingering of mental health disorders in forensic settings. However, clinicians do not always have these tools readily available to them. Therefore, we have focused our investigation on verbal and nonverbal behaviours that may be indicators of deception used to identify cases of feigning or malingering. Despite the large body of existing research on cues to deception, we currently have no reliable cues that proceed or accompany deception related to feigning or malingering a psychological disorder. Through a series of four studies we aimed to identify cues to deception that are exhibited when feigning symptoms of PTSD. The aim of Study 1 was to examine: personality traits (i.e., Introversion / Extroversion and Psychoticism) that may moderate the ability to deceive; emotional and physiological arousal (i.e., heart rate variability [HRV]) associated with deception; and the influence of these variables on peoples’ confidence in their own ability to deceive. Our findings indicated that emotional and physiological arousal related to the thought of enacting deception correlated with emotional and physiological arousal related to stress. However, emotional arousal associated with stress or deception was not correlated with physiological arousal associated with stress or deception. Therefore, we were unable to identify a consistent pattern of emotional and physiological responding associated with the thought of being deceitful. In addition: deception confidence was not correlated to the physiological arousal (i.e., HRV) associated with deceit; Psychoticism had no impact on emotional or physiological arousal associated with deception or deception confidence; and Introversion / Extroversion was not correlated to physiological arousal associated with deception. However, people higher on Extraversion reported more subjective distress after thinking about enacting deception than people higher on Introversion. During this study we identified the trait of Psychoticism as needing further investigation. Subsequently, in Study 2 we further examined deceivers who were low and higher in Psychoticism. We examined: verbal and nonverbal behaviours displayed when telling the truth and deceiving; verbal and nonverbal behaviours of deceivers who were low and higher in Psychoticism; and verbal and nonverbal behaviours of more and less credible deceivers. Deception confidence and perceived credibility (as judged by raters) were also considered. Most notably, we found that people smile less when deceiving. This is different to evidential deception research. Findings indicated that deceivers higher in Psychoticism displayed unique behavioural cues. However, Psychoticism did not moderate deception confidence or perceived credibility (as judged by raters). In Study 3, we again examined verbal and nonverbal behaviours displayed when telling the truth and enacting deceit. We also assessed the verbal and nonverbal behaviors of differentially motivated deceivers, and people who were more and less prepared to deceive. Deception confidence and perceived credibility were again considered. Findings indicated that participants in this sample displayed less eye movements, raised their eyebrows less, were less facially expressive, smiled less, and pursed their lips more when deceiving. More motivated deceivers and more prepared deceivers displayed unique behaviours and motivated deceivers spent more time preparing to deceive. However, deception preparation did not impact deception confidence or perceived credibility. The main aim of Study 4 was to examine the deception detection ability of psychology students, and the difference in deception detection ability between undergraduate and postgraduate psychology students. We also investigated the impact of law enforcement experience, legal experience, and psychology work experience on the ability to detect deception. Findings indicated: students were not better than chance (if we assume chance is 50%) at making lie / truth judgments; postgraduates were better deception detectors than undergraduates; experience with law enforcement and psychology work experience were positively correlated to deception detection ability; deception detectors were better able to identify deceivers who were less motivated to feign PTSD; confidence in people’s own ability to detect deception was not related to their actual ability to detect deception; and deception detectors did not rate truthtellers as more credible than deceivers. Overall, we find that deception of mental health symptoms leads to different cues than those found in evidential research. We also conclude that Psychoticism may lead to differential behavioural cues when deceiving, as do motivation and preparation time. People are not good at detecting deceit, but experience with psychology and life experience seems to be predictors in the case of detecting feigned trauma symptoms. Methodological limitations of the current studies include: the failure of the deception task to evoke strong physiological arousal in Study 1; the lack of high psychoticism deceivers in Study 2; the disparity in the duration of the two videos used in experiments 2 and 3; the disparity in credibility scores of the more credible deceivers group between Studies 2 and 3; and the inclusion of only one independent rater in Studies 2 and 3. Additionally, in comparison to the financial remuneration often gained through successful feigning or malingering of PTSD, the financial incentive offered in Studies 2 and 3 is nominal. These limitations are addressed in the general discussion of this thesis.

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Thesis (PhD Doctorate)

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Doctor of Philosophy (PhD)


School of Applied Psychology

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Post Traumatic Stress Disorder


nonverbal behaviours

verbal behaviours



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