Strong, but wrong: lay people's and police officers' beliefs about verbal and nonverbal cues to deception

The present study investigated the beliefs of students and police officers about cues to deception. A total of 95 police officers and 104 undergraduate students filled out a questionnaire addressing beliefs about cues to deception. Twenty-eight verbal cues were included in the questionnaire, all extracted from verbal credibility assessment tools (i.e., CBCA, RM, and SCAN). We investigated to what extent beliefs about nonverbal and verbal cues of deception differed between lay people (students) and police officers, and whether these beliefs were in agreement with objective cues known from research. Both students and police officers believed the usual stereotypical, but non-diagnostic (nonverbal) cues such as gaze aversion and increased movement to be indicative of deception. Yet, participants were less inclined to overestimate the relationship between verbal cues and deception and their beliefs fitted better with what we know from research. The implications of these findings for practice are discussed.

A structured questionnaire study comparing 95 active police officers and 104 undergraduate students on their rated confidence in 28 verbal cues (from CBCA, RM, SCAN) and nonverbal cues as deception indicators, with results compared against meta-analytic findings on actual cue validity.

This study investigated a critical gap between scientific evidence and practitioner beliefs in deception detection by examining whether police officers and lay people's beliefs about verbal cues—derived from widely-used forensic assessment tools (CBCA, RM, SCAN)—better reflect research evidence than their beliefs about nonverbal cues. Using a questionnaire approach with 95 police officers and 104 students, researchers assessed participants' confidence ratings in 28 verbal cues and stereotypical nonverbal indicators, comparing responses to meta-analytic findings on actual cue validity. The results revealed that both groups held similarly inaccurate beliefs about nonverbal cues such as gaze aversion and fidgeting, indicating that professional training and experience do not protect against common deception myths. However, beliefs about verbal cues showed somewhat better alignment with research evidence, with smaller magnitude errors than nonverbal beliefs. Critically, no significant differences emerged between police officers and students, suggesting current training practices may be inadequate.

The findings highlight a concerning disconnect between the empirical foundation of credibility assessment tools and practitioners' understanding of their diagnostic value, with implications for training standards and the reliability of investigative interviews. This suggests that practitioner training on verbal assessment tools requires enhancement to improve alignment with research evidence and reduce reliance on debunked nonverbal indicators.

Background & Context

The ability to detect deception remains one of the most challenging tasks in forensic and investigative settings. Despite a large body of research showing that deception cannot be reliably inferred from behavior, practitioners and laypeople continue to rely on stereotypical cues that lack empirical support. This persistent gap between scientific evidence and practitioner beliefs has serious implications for criminal justice outcomes.

This 2016 study by Bogaard and colleagues addresses a critical question in deception detection: whether beliefs about verbal cues to deception—drawn from established credibility assessment tools—align better with research evidence than beliefs about nonverbal cues. Previous studies from the UK, Netherlands and Sweden comparing professionals and lay persons revealed that professionals typically hold as many incorrect nonverbal beliefs about deception as lay people. The investigation of verbal cue beliefs represents an important extension of this literature.

The study specifically examined twenty-eight verbal cues extracted from verbal credibility assessment tools (i.e., CBCA, RM, and SCAN)—methods widely used in forensic contexts for statement analysis. Understanding whether these tools reflect empirically validated indicators, and whether practitioners accurately understand their diagnostic value, has direct implications for training and practice standards.

Research Design & Methodology

The study investigated the beliefs of 95 police officers and 104 undergraduate students about cues to deception through a structured questionnaire approach. The police officers represented active practitioners with real-world experience in investigative interviewing, while undergraduate students served as a lay comparison group representing general public beliefs.

The questionnaire assessed beliefs about both nonverbal behavioral cues (the stereotypical indicators like gaze aversion and fidgeting) and 28 verbal cues systematically extracted from three established verbal credibility assessment frameworks:

• Criteria-Based Content Analysis (CBCA) – a structured method evaluating statement quality and detail
• Reality Monitoring (RM) – an approach distinguishing experienced from fabricated memories
• Scientific Content Analysis (SCAN) – a technique analyzing linguistic patterns in statements

Researchers investigated to what extent beliefs about nonverbal and verbal cues differed between lay people and police officers, and whether these beliefs were in agreement with objective cues known from research. Participants rated the extent to which various cues indicated deception, allowing direct comparison with meta-analytic findings on actual cue validity.

Results & Key Findings

The study revealed a striking pattern: both students and police officers believed the usual stereotypical, but non-diagnostic nonverbal cues such as gaze aversion and increased movement to be indicative of deception. This finding confirms that professional training and experience do not inoculate officers against common deception myths.

However, the results for verbal cues presented a more nuanced picture:

• Participants were less inclined to overestimate the relationship between verbal cues and deception
• Beliefs about verbal indicators from CBCA, RM, and SCAN fitted better with what we know from research
• Incorrect beliefs about cues to deception are not confined to gaze aversion, but the magnitude of error was smaller for verbal than nonverbal cues

The study found no significant difference between police officers and students in the accuracy of their beliefs about either verbal or nonverbal cues, suggesting that current training practices are insufficient to align practitioner knowledge with scientific evidence. Both groups demonstrated similar patterns of overconfidence in invalid nonverbal indicators while showing relatively better calibration for verbal statement characteristics.

Discussion & Significance

These findings reveal a fundamental asymmetry in deception detection beliefs: people hold strong but wrong convictions about nonverbal behavior while maintaining more research-consistent (though still imperfect) beliefs about verbal content. This pattern may reflect deeper cognitive biases, as people tend to rely heavily on nonverbal cues when making deception verdicts, despite their poor diagnostic value.

The relative accuracy of verbal cue beliefs is particularly significant given that verbal content analysis methods like CBCA have stronger empirical support than nonverbal indicators. The study suggests that practitioners may benefit more from focusing on statement content rather than behavioral observation—yet their actual practice often emphasizes the less valid nonverbal domain.

The absence of expertise effects between police officers and students is concerning for professional practice. It suggests that professional experience alone does not improve deception detection beliefs, and may even reinforce misconceptions through confirmation bias when stereotypical cues occasionally co-occur with deception by chance. This underscores the need for evidence-based training programs that actively challenge common myths rather than reinforcing intuitive but incorrect assumptions.

Limitations & Considerations

The study measured beliefs about cues rather than actual deception detection performance, leaving open the question of whether inaccurate beliefs necessarily translate to poor detection accuracy. Subsequent research by the same authors has explored this relationship, but the current study focuses on the belief-evidence gap rather than operational outcomes.

The police officer sample, while representing active practitioners, may not capture the full range of specialized training approaches used in different jurisdictions. Some advanced interview training programs (such as those emphasizing cognitive interview techniques or conversation management) may produce different belief patterns than observed in this Dutch sample.

The reliance on self-report questionnaires cannot capture the complex, dynamic process of real-world credibility assessment, where multiple cues are integrated over extended interactions. Laboratory beliefs may not fully reflect how practitioners weight different cues when conducting actual interviews with genuine consequences.

Practical Applications

For polygraph examiners and law enforcement professionals, this research provides a clear mandate: refocus attention from behavioral observation to statement content analysis. Training programs should explicitly address and debunk nonverbal deception myths while strengthening skills in systematic verbal credibility assessment using validated frameworks like CBCA.

For consumers and the legal system, the findings underscore caution regarding expert testimony based on behavioral analysis or "body language reading." The study demonstrates that even experienced professionals harbor misconceptions about deception cues that align more with popular stereotypes than scientific evidence. Credibility assessments should rely on structured, validated methods with documented accuracy rather than subjective behavioral impressions, regardless of the evaluator's experience level.