Verbal cues to deceit when lying through omitting information: Examining the effect of a Model Statement interview protocol

This study examined whether the Model Statement interview technique can enhance detection of verbal cues when people lie by omitting information rather than fabricating false details. Results showed truth tellers reported more complications than lie tellers, while the Model Statement increased overall detail reporting but did not amplify veracity differences.

A 2×2 experimental design with 152 participants who watched a video and either truthfully recalled events or omitted one person's presence, with half receiving a Model Statement interview technique.

This laboratory study addressed the understudied area of lies of omission by testing whether Model Statement interview techniques could enhance verbal cue detection when deceivers withhold rather than fabricate information. Participants viewed a secret meeting video and either recalled it truthfully or omitted one person's presence, with half exposed to a detailed Model Statement example. Truth tellers consistently reported more complications than lie tellers, establishing complications as a diagnostic cue for omission-based deception. Notably, lie tellers provided more total details than truth tellers, contrasting with fabrication studies where truth tellers typically provide more information. The Model Statement increased overall reporting but did not amplify veracity differences between groups.

These findings suggest that complications serve as a reliable verbal indicator for detecting lies of omission, offering practitioners a specific cue to focus on when suspects may be withholding rather than fabricating information during interviews.

Background & Context

Deception detection research has historically focused on outright lies—false statements that contradict known truths. However, practitioners frequently report that lying through omitting information is highly relevant to their work, yet this critical form of deception has been largely ignored by verbal lie detection researchers. Omission lies present a unique challenge: everything the deceiver says may be entirely truthful, making traditional detection approaches ineffective when independent evidence is unavailable.

This study addresses a crucial gap by examining whether the Model Statement interview technique can enhance detection of verbal cues when people lie by omission. The Model Statement—a detailed example account unrelated to the investigation topic—has shown promise in eliciting information and detecting fabricated lies. In prior omission lies experiments examining various types of details, complications emerged as the most diagnostic veracity cue. This research extends that work by testing whether the Model Statement amplifies these verbal differences between truth tellers and lie tellers in omission scenarios.

Research Design & Methodology

Participants watched a video recording of a secret meeting between three people, with truth tellers instructed to recall the meeting truthfully and lie tellers instructed to pretend that one person (John) was not there. This created an ecologically valid omission lie scenario where deceivers reported genuine information while strategically withholding key details.

A G*Power analysis determined that at least 141 participants were needed to achieve 99% power with a medium effect size (f² = 0.15); the study recruited 157 participants, with five excluded due to non-compliance or recording failures, yielding a final sample of 152. The experimental design employed a 2×2 between-subjects factorial structure:

• Veracity condition: Truth tellers vs. lie tellers (omitting one person)
• Model Statement condition: Exposed vs. not exposed to detailed example account
• Dependent measures: Total details and complications reported
• Statistical approach: ANCOVA with participant status as covariate, plus equivalence testing

Interviews were conducted with initial free recall followed by the Model Statement (when applicable) and then a second recall phase. Rapport was measured using the nine-item Interaction Questionnaire to ensure interview quality.

Results & Key Findings

Truth tellers reported more complications than lie tellers, but lie tellers reported more details than truth tellers. This counterintuitive finding regarding total details distinguishes omission lies from fabrication-based deception, where truth tellers typically provide more information.

Key statistical outcomes:

• Complications: Truth tellers reported significantly more complications than lie tellers in Phase 1, with equivalence testing not supporting the null hypothesis
• Model Statement main effect: The Model Statement resulted in more complications and details being reported by both groups
• Interaction effect: The Veracity × Model Statement interaction effect was not significant
• Consistency across studies: Truth tellers reporting more complications than lie tellers was found in each of the previous four omission lies experiments examining complications

The robust complications finding is particularly significant. Complications—occurrences that make situations more complex to report, such as "I forgot my phone, so had to use my friend's phone to call my mum"—emerged as the most diagnostic veracity cue across multiple omission deception experiments.

Discussion & Significance

This research strengthens the evidence that complications serve as a reliable verbal indicator of truthfulness in omission lie scenarios, even when total detail counts prove unreliable or misleading. The finding that lie tellers reported more total details than truth tellers contradicts traditional deception research patterns and reveals important strategic differences: when omitting information, liars may compensate by elaborating on non-omitted elements to appear thorough and credible.

The Model Statement's effectiveness as an information elicitation tool was confirmed—it increased output from both groups without differentially benefiting truth tellers. However, the complications result strengthens the notion that complications is a diagnostic veracity indicator in omission lies. This suggests practitioners should focus on qualitative verbal markers (complications) rather than quantitative measures (total details) when evaluating statements where omission is suspected.

The study's theoretical contribution lies in demonstrating that omission lies require different detection approaches than fabrication-based lies. Strategic omitters employ a "keep it simple" strategy that specifically avoids complications—unnecessary complexities that would make their censored narrative harder to maintain—while potentially adding detail to non-omitted portions to project completeness.

Limitations & Considerations

The laboratory setting, while offering experimental control, differs from high-stakes investigative interviews. Participants watched a brief video rather than experiencing events directly, which may reduce the richness of genuine memories and the cognitive challenges of real-world omission scenarios. The specific omission task—pretending one person wasn't present—represents just one type of information omission that practitioners encounter.

The lack of a significant Veracity × Model Statement interaction suggests the Model Statement does not amplify differences between truth tellers and lie tellers in omission scenarios as it does in some fabrication contexts. Additionally, the study examined only two dependent variables; other verbal markers might reveal additional differences or interaction effects with the Model Statement technique.

Practical Applications

For investigators and examiners suspecting omission-based deception, this research provides clear guidance: assess complications rather than total detail counts. When interviewees describe events, listen for occurrences that made situations more difficult or complex—confusion, unexpected obstacles, changes in plans. Truth tellers naturally include these elements; omission liars systematically avoid them to maintain narrative simplicity.

The Model Statement remains valuable in omission lie interviews as an information elicitation tool, encouraging fuller disclosure from both truthful and deceptive interviewees. However, practitioners should not expect it to magnify veracity differences. Instead, use it to maximize information output, then apply complications analysis to the resulting narrative. This dual-pronged approach—elicit comprehensively, then evaluate qualitatively—offers the most promising pathway for detecting lies of omission when corroborating evidence is unavailable.