1. Motivated to lie: The effects of incentives on characteristics of truthful and deceptive informant reports
Carroll A. Boydell & J. Don Read
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Introduction
Informants - those who report perpetrators’ admissions to crime - have provided important evidence used to convict criminals throughout history (Madinger, 2000). However, jailhouse informants have also contributed to convictions of innocent persons, testifying in an estimated 15% of wrongful conviction cases (Centre on Wrongful Convictions, 2005) To encourage informants to testify in court, they can be offered incentives such as money or reduced prison sentences. Yet despite the expectation that incentives should increase all reports of criminal admissions, incentives appear to increase the likelihood that false but not true admissions will be reported (Swanner et al., 2010). Thus, such offers may attract deceptive informants who merely want to acquire benefits for themselves It is possible, however, that incentives may affect informants’ motivations and behaviours in ways that make it easier to distinguish honest from deceptive reports. For incentivized informants, the stakes of being perceived by legal authorities as honest are likely higher than for individuals who do not receive incentives. As the stakes of lies increase, so should behavioural differences exhibited between liars and truth-tellers (e.g., Porter & ten Brinke, 2010). Thus, honest and deceptive incentivized informants may differ more in exhibited behaviours than those who do not receive incentives. Thus, the purpose of the current experiment was to explore how incentives affect behaviours of informants as they recount criminal admissions.
Methods (cont’d)
.Another one-third of participants, assigned to the Negative Incentive condition, were told that if they were unsuccessful in convincing the rater, they would have to return to participate in four additional hours of research. Remaining participants were told to try their best in recalling the admission (No Incentive condition). One week later, participants were video-recorded reporting the admission elicited via an abbreviated version of the Cognitive Interview.
The videos, as well as transcripts of the interviews were coded by two raters blind to participant conditions for a sample of verbal (first person pronouns, exclusive words, spontaneous corrections, reproductions of conversations, and cognitive operators), paraverbal (repeated phrases, speech errors, speech hesitations, response latency, and speech rate), and nonverbal cues (illustrators, limb and finger movements, blinking, smiling, and fidgeting) found in previous research to distinguish liars from truth-tellers. The frequency of each cue was totaled for each participant, then divided by total word count (for verbal and paraverbal cues) or length of interview in seconds (for nonverbal cues) to control for interview length. Inter-rater analyses, conducted on 10% of cases, indicated 90% agreement across all cues initially, then 100% upon discussion. * * *
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Results
Three multivariate ANOVAs examined the effects of Veracity and Incentive on rates of verbal, paraverbal, and nonverbal cues exhibited during participants’ accounts, respectively. Contrary to hypotheses, significant effects of Incentive were not yielded via any of the three analyses [Fs < 1.53 , ps > .13; Wilks Lambda]. A series of F-tests, comparing rates of examined cues within each Incentive condition between the Honest and Deceptive conditions, revealed that for two cues, incentive instructions did increase the difference in mean exhibited cues relative to the control group between Honest and Deceptive participants (see Figures 1 & 2). However, these analyses also revealed that for six cues, means rates of each cue between Veracity conditions only differed if participants had not received incentive instructions (Fs > 5.69, ps < .03; see Figures 3-8). That is, incentive instructions appeared to reduce any differences in cues exhibited between Honest and Deceptive participants detected in the absence of such instructions.
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Hypothesis
It was predicted that differences in behavioural cues exhibited by honest versus deceptive informants as they recalled a criminal admission would be greater for incentivized than non-incentivized participants. * *
Methods
84 undergraduates participated in this study for course credit. In Session 1, participants were told they would view a videotaped admission to an assault, robbery, and murder. All participants heard a description of the contents of the admission. One-half of participants were randomly assigned to hear the admission and return to the lab one week later to recount it (Honest condition). The other half watched a video of the perpetrator answering questions about himself but did not hear him admit to any crimes. As such, each provided a fabricated account in Session 2 (Deceptive condition). All participants were told an independent rater would be viewing their account and that they must convince the rater that their admission report was honest and accurate.
Prior to leaving Session 1, two-thirds of participants were given incentive instructions. One-third of participants were randomly assigned to a Positive Incentive condition, whereby they were told that if they convinced the independent rater that they recalled the admission honestly and accurately, they would be entered into a draw for $200. (Methods cont’d on right) 
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Conclusion
The purpose of this study was to examine the effect that incentives have on cues exhibited while reporting a criminal admission. Preliminary results indicate that incentives may, in some cases, result in changes in informants’ behaviours that increase the similarity of rates of behavioural cues exhibited by truthful and deceptive informants. This finding is notable in light of the assertion that reliable detection of lies based on behavioural cues requires that the lies told be high stakes (e.g., O’Sullivan & Ekman, 2004). Offering incentives may in fact complicate the detection of deception in informants. Future research should examine this issue further by exploring the effect of incentives on a greater variety of cues in a larger sample of participants. * *
* = p < .05