Abstract
The study aimed to investigate whether a combination of the P3-based Guilty Knowledge Test (GKT) and reality monitoring (RM) distinguished between individuals who are guilty, witnesses, or informed, and using both tests provided more accurate information than did the use of either measure alone. Participants consisted of 45 males that were randomly and evenly assigned to three groups (i.e., guilty, witness, and informed). The guilty group conducted a mock crime where they intentionally crashed their vehicle into another vehicle in a virtual environment (VE). As those in the witness group drove their own vehicles, they observed the guilty groups' vehicle crash into another vehicle. The informed group read an account and saw screenshots of the accident. All participants were instructed to insist that they were innocent. Subsequently, they performed the P3-based GKT and wrote an account of the accident for the RM analysis. A higher P3 amplitude corresponded to how well the participants recognized the presented stimulus, and a higher RM score corresponded to how well the participants reported vivid sensory information and how much less they reported uncertain information. Findings for the P3-based GKT indicated that the informed group showed lower P3 amplitude when presented with the probe stimulus than did the guilty and witness groups. Regarding the RM analysis, the informed group obtained higher RM scores on visual, temporal, and spatial details and lower scores on cognitive operations than the guilty and witness groups. Finally, discriminant analysis revealed that the combination of the P3-based GKT and RM more accurately distinguished between the three groups than the use of either measure alone. The findings suggest that RM may build upon a weakness of the P3-based GKT's. More specifically, it may build upon its susceptibility to the leakage of information about the crime, therefore helping protect innocent individuals who have information about a crime from being perceived as guilty.
Highlights
Deception occurs in a variety of interpersonal situations
The aim of this study was to investigate whether a combination of the P3-based Guilty Knowledge Test (GKT) and reality monitoring (RM) would more effectively differentiate among guilty individuals who conduct a crime, witnesses who experience the crime, and informed individuals who did not experience the crime but have information about the crime
We investigated whether the combination of the P3-based GKT and RM would more accurately discriminate among the groups than either test alone
Summary
Deception occurs in a variety of interpersonal situations. Individuals are able to detect deception using several methods. When an individual tells a lie, that person unconsciously displays potential cues that may be behavioral, verbal, and psychophysiological (Vrij, 2000; Gamer et al, 2006). One commonly used lie detection tool is the arousal-based polygraph (Vrij, 2000). The arousal-based polygraph indirectly detects a lie by measuring variables related to the lie (e.g., guilty, anxiety). These emotions can appear in a situation where individuals tell a lie and in an uncertain situation where innocent individuals are false accused (Allen and Mertens, 2009)
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