The effect of embedded lies on the verbal quality of statements and implications for credibility assessment

  • Brianna L. Verigin

Student thesis: Doctoral Thesis


Embedded lies, the topic of investigation in this thesis, have been under researched within the deception detection literature. The overarching aim of this research was to examine how interviewees’ strategic inclusion of both truths and lies within a single account may affect statement quality, and the subsequent implications for verbal lie detection.

Across three experimental studies and one exploratory survey, I (i) explored the deception strategies reported by people who claim to be good liars (Chapter 2), (ii) examined how the combination of truths and lies within a single account affects the verbal quality of statements (Chapters 3 and 4), and (iii) tested if embedded lies can be exploited to facilitate within-statement lie detection (Chapter 5). Chapter 2 (n = 194) explored deception by investigating how laypeople’s self-reported ability to deceive was associated with their lie frequency, characteristics, and deception strategies. Of particular interest was whether the strategic inclusion of truthful details into lies corresponded to higher perceptions of deception ability. Results showed that self-reported good liars reported embedding lies as their most common strategy for deceiving successfully. Chapter 3 (n = 144), experimentally tested how interviewees strategically regulate the information they provide when their accounts contain both truthful and deceptive information. Results showed that interviewees calibrated the richness of detail provided in the first element of their statement to be consistent with the veracity of the second element, such that elements followed by a lie were less detailed than elements followed by a truth. Further examination revealed that participants also calibrated their lies according to both the preceding and the following element, with lies becoming more detailed when they were flanked by truthful information compared to when they were flanked by other lies. In light of these results, Chapter 4 (n = 111) examined whether embedded lies differed qualitatively from full fabrications. The results showed that the two types of lies did not differ on a number of content-based cues (e.g., detail richness), but that lies embedded in otherwise truthful statements could be distinguished from truths embedded in truthful statements on the basis of detail richness and statement quality (i.e., clarity and plausibility). Finally, Chapter 5 (n = 148) tested whether lie detection accuracy could be improved by using embedded lies as a within-statement baseline comparison. Contrary to the hypothesis, results showed that instructing participants to make a within-statement baseline comparison did not increase the accuracy of their veracity assessments.

Taking the results of these studies together, it could be concluded that liars aim to strategically maintain consistency regarding the quality of information provided between truths and lies within their statements; however, content-based methods of verbal credibility assessment based on the cues measured in this research appear to be robust against this strategy. The results of this thesis emphasise that lie detectors should exploit liars’ attempts at maintaining consistency by utilising methods of verbal baselining that control for both the individual and the situation.
Date of AwardDec 2019
Original languageEnglish
Awarding Institution
  • University of Portsmouth
SupervisorZarah Vernham (Supervisor), Aldert Vrij (Supervisor) & Sharon Leal (Supervisor)

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