Examining Different Types of Comparison Questions in a Field Study of CQT Polygraph Technique

Field study comparing different types of comparison questions in real criminal investigations, examining the practical effectiveness of exclusive and non-exclusive formats.

Field study in actual criminal investigations comparing outcomes from exclusive and non-exclusive comparison question formats.

Ginton's field study examined different comparison question formats under real investigative conditions, providing practical evidence that both exclusive and non-exclusive comparison questions produce effective physiological discrimination in operational settings. This finding has practical significance for examiner flexibility in question construction while maintaining test validity.

The validation of multiple comparison question formats gives practitioners flexibility in adapting questions to specific case circumstances without sacrificing accuracy.

Background & Context

The comparison question has been the cornerstone—and the most controversial element—of the Comparison Question Test (CQT) since John Reid first integrated it into the test format in 1947. For decades, practitioners have debated which type of comparison question produces the most effective physiological differentiation: Reid's Probable Lie format (later termed Non-Exclusive), Backster's Exclusive format with temporal restrictions, or Raskin's Directed Lie questions introduced in the 1980s.

Ginton's 2017 study addresses a fundamental theoretical question that had remained largely unexplored in field conditions. The research was actually conducted in 1981-1982 when Dr. Avital Ginton headed all polygraph activities in Israel National Police, though it was formally published decades later. This study challenges orthodox CQT theory by testing whether comparison questions must contain actual lies about past misdeeds to function effectively.

The research gains particular significance within the context of Ginton's Relevant Issue Gravity (RIG) strength framework, which proposes that the salience of questions—rather than their specific content or truth value—drives physiological responsiveness in truthful examinees.

Research Design & Methodology

The research was integrated into real-life examination of ongoing arson cases at an Air Force base over one year, during which over 300 alleged suspects were polygraphed, with 21 examinees receiving a unique test format. This naturalistic integration into actual criminal investigations represents a methodological strength rarely achieved in polygraph research.

Each of the 21 examinees was administered a CQT containing three relevant questions about warehouse fires alongside three distinctly different types of comparison questions:

• Probable Lie Question (traditional): "Have you ever damaged any public property?"
• Hypothetical Question: "Assuming you have very good reasons and opportunity, would you damage any public property out of rage or for pure fun?"
• Bizarre Question: "Do you like blue in particular?" (introduced with elaborate pretest discussion to increase salience)

The bizarre color question was introduced with statements emphasizing its importance, followed by several minutes discussing the examinee's habits and personality traits related to the color blue, thereby increasing the question's salience. The specific phrasing was tailored during pretest to ensure a "no" answer.

Three examiners independently judged each chart repetition, ranking the physiological responses of the three comparison question types by relative strength—strongest received 1 point, second received 2 points, weakest received 3 points. This ranking methodology focused on comparative reactivity rather than absolute numerical scoring.

Results & Key Findings

All three comparison question types produced statistically equivalent physiological responses. The probable lie comparison question received a mean total of 1.94, the hypothetical comparison question 2.14, and the bizarre comparison question 1.91—differences too small to be meaningful.

The core finding challenges fundamental CQT theory:

• No significant differences in physiological reactivity across the three comparison question formats
• The bizarre question about color preference—containing no lie whatsoever—functioned as effectively as traditional probable lie questions
• Hypothetical future-oriented questions produced responses comparable to questions about actual past behavior

Results suggest that with truthful examinees, comparison questions which do not incorporate any lies to be afraid of their exposure, or any lies at all, might function similarly to probable lie questions, by just increasing their salience in a manner that presumably creates some concerns about them. This finding fundamentally questions whether the "lie" component of comparison questions is theoretically necessary.

Many field examiners feel that what makes the question effective and responsive regardless of the format is the manner in which the comparison question is introduced to the examinee in the pretest, and Ginton's research supports this notion.

Discussion & Significance

These findings carry profound theoretical implications for understanding CQT mechanisms. Traditional "psychological set" theory holds that comparison questions must involve probable lies about past misdeeds to capture the truthful examinee's attention. Ginton's data directly challenge this assumption, demonstrating that question salience—not deceptiveness—appears to be the critical factor.

The results align with Ginton's Relevant Issue Gravity (RIG) framework, which proposes that CQT effectiveness depends on the differential allocation of cognitive resources between relevant and comparison questions. For innocent examinees with relatively low RIG strength, attention can be diverted away from relevant questions by any sufficiently salient comparison stimulus—whether it involves actual deception, hypothetical scenarios, or even seemingly irrelevant topics like color preference.

This research provides field validation for examiner flexibility in question construction. The findings challenge the Psychological Set theory by suggesting there is no need to build comparison questions on past misdeeds of the examinee, nor is there any need to build them on any kinds of lies at all. What matters is strategic question introduction during pretest to establish appropriate psychological salience.

Limitations & Considerations

The study's primary limitation is its modest sample size of 21 examinees, reflecting the challenges of controlled experimentation within genuine criminal investigations. The study was considered internal research of the Scientific Interrogation Lab of Israel National Police and was never officially published outside the Lab until decades after data collection, meaning contemporary peer review occurred long after the original work.

Originally the relevant questions were compared to all three comparison question types with similar outcomes, but unfortunately the exact data to enable statistical analysis could not be traced. This represents a significant loss of potentially valuable information about diagnostic accuracy with different question formats.

The research focused primarily on truthful examinees' responses. The study does not provide comprehensive data on how these different comparison question formats perform with deceptive examinees, leaving questions about differential accuracy rates across ground-truth categories. Additionally, ground truth was never conclusively established for most cases, limiting validation of actual diagnostic accuracy.

Practical Applications

This research liberates examiners from rigid adherence to specific comparison question formats. Practitioners can adapt question construction to the unique demands of each case, focusing on creating sufficient psychological salience through strategic pretest presentation rather than adhering to prescribed question content. The findings suggest that questions about hypothetical behaviors or even carefully introduced neutral topics may serve comparison functions effectively.

For consumers and stakeholders, these findings underscore that CQT validity depends heavily on examiner skill in question formulation and pretest procedures—not merely on following standardized question templates. The emphasis shifts from question content to question presentation, highlighting the importance of examiner training in strategic communication and psychological preparation of examinees. This flexibility may improve test applicability across diverse investigative contexts while maintaining diagnostic effectiveness.