COMPONENTE SOCIAL:

10.1. Introduction

In the introductory chapters of the present thesis, attention was drawn to the possible importance of considering multiple channels of behaviour when attempting to detect deception. Several leading researchers have suggested that the more cues to deception that a person exhibits, the more likely that person is to be lying (for example, DePaulo et al., 2003; ten Brinke & Porter, 2012; Vrij & Mann, 2004). The studies presented so far have examined subjective observer ratings, and verbal cues to deception; the study presented in this chapter, Study 6, adds to these by investigating nonverbal cues to deception in the same, larger sample of appeals used in Studies 4 and 5. As with verbal cues, some nonverbal behaviours are amenable to frequency counts and, therefore, may be more objectively measured, making them particularly useful for applied purposes.

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As has previously been noted, the findings regarding several nonverbal cues to deception in high stakes contexts have been mixed; for example, gaze aversion has been found to relate to deception in some studies (Vrij & Mann, 2001a; Wright Whelan, 2009), but to have no relationship to veracity in another study (Mann et al., 2002). Similarly, the findings regarding hand movements and blink rate have been equally inconsistent: self-adaptors and illustrators were found to decrease during deception in one study (Koper & Sahlman, 1991), gesticulation was found to increase during deception in another study (Davis et al., 2005), and hand movements were found to be unaffected by veracity in another study (Mann et al., 2002); blink rate has been found to decrease (Mann et al., 2002), and to increase (ten Brinke & Porter, 2012), during high stakes deception. Head shaking has been found to relate to deception in two investigations of high stakes deceptive communication (Davis et al., 2005; Mann et al., 2006), and shrugging was related to deception in one study as part of a ‘nonverbal overdone’ measure (Davis et al., 2005). In general, the findings regarding nonverbal behaviours in high stakes contexts are scant and patchy, and there is clearly a need for further investigation of this channel of behaviour.

Nevertheless, on the basis of previous research, it was hypothesised that some nonverbal cues to deception, previously identified in high stakes situations, would generalise to this appeals context. Gaze aversion and head shaking, both of which have been shown to relate to deception across high stakes contexts, were particularly expected to relate to deception in the context of appeals. The inclusion of shrugging as a cue was more speculative, as there is very little previous research on this behaviour in high stakes contexts. The present study did not include an investigation of cues specifically derived from Study 1 of the present thesis, as the only nonverbal

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cue amenable to frequency counts identified in Study 1 was gaze aversion, which, as mentioned above, has been identified in previous deception research.

As in Studies 2, 3, 4, and 5, case by case analyses were again conducted as it was hypothesised that the use of a combination of cues to classify cases (appeals) as honest or deceptive, would achieve high accuracy rates in discriminating between liars and truth-tellers. These analyses included combining verbal and nonverbal cues to classify cases, as it was considered that combining information from cues across two channels of behaviour, which are also amenable to frequency counts, would have the greatest utility in an applied context, and would be more accurate than case by case analyses using a single channel of behaviour. The final part of the case by case analyses involved combining the information from verbal cues, nonverbal cues, and cues subjectively rated by observers, to classify individual cases as honest or deceptive.

10.2 Method

10.2.1. Materials and Procedure

The same 32 appeals for help with missing or murdered relatives (16 honest and 16 deceptive) used in Studies 4 and 5 were used in this study.

Again, following protocols established in previous research on high stakes deception (Mann et al., 2002; ten Brinke & Porter, 2012), one coder counted frequencies of predetermined behaviours in the video clips, and a second coder, who was blind to the veracity of the appeals, coded a random sample of 25% of the

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deceptive appeals and 25% of the honest appeals. Both coders were graduate students studying deception. Inter-rater reliability for the frequency counts was high, ranging from r = .93 to r = .1.00 (see Table 10.1). As the inter-rater reliability for the frequency counts was high for the random sample, frequency counts produced by the coder who had coded all the transcripts were used in all analyses.

The behaviours included in the study were nonverbal cues to deception amenable to measurement by frequency counts, identified in previous research on real life, high stakes lies. The cues under consideration were in some ways proscribed by the footage available; for example, despite previous findings suggesting that blink rate may be related to deception in high stakes contexts (Mann et al., 2002; ten Brinke & Porter, 2012), in most cases the quality of the video clips was not of a sufficiently high standard to measure blink rate. Similarly, despite previous findings suggesting that the use of hand movements may be related to deception in high stakes contexts (Davis et al., 2005; Koper & Sahlman, 1991), in a large proportion of the appeals the hands were not visible, so that it was not possible to investigate the use of hand movements.

Gaze aversion was included as a cue in the present study, as the findings regarding this cue in the literature on high stakes deception have been mixed, and it therefore clearly warrants further investigation. Hence although in Study 4 of the present thesis, gaze aversion as a cue rated subjectively by observers did not achieve significant inter-rater reliability, it was considered useful to investigate this behaviour with more objective frequency counts. Appealers were coded as averting their gaze when they were not looking directly at the cameras or interviewer, but instead looked down, up or to the side. Appealers who were wearing sunglasses or hats so that their eyes were not visible, or whose eye-line was unclear, were not