Comparison Test Formats in Polygraph: Complete CTF Guide

What Is the Comparison Test Format?

The Comparison Test Format (CTF) is a family of structured polygraph examination techniques that form the foundation of modern psychophysiological detection of deception (PDD). The central principle underlying all CTF variants is powerful in its elegance: by comparing an examinee's physiological responses to direct investigation questions (relevant questions) against their responses to broader, less specific comparison questions, an examiner can differentiate between truthful and deceptive individuals.

This methodology rests on the understanding that deceptive individuals demonstrate greater autonomic nervous system arousal when confronted with relevant questions about the specific issue under investigation, while truthful individuals show relatively greater concern and reactivity to comparison questions that touch on broader past behaviors or moral issues. The differential response pattern between these two question categories enables trained examiners to make informed decisions about truthfulness. Research has provided empirical support for the psychological processes driving CQT accuracy [7]Verified The Role of Comparison Questions in Physiological Detection of Deception
Confirms mock crime study with 120 participants showing comparison questions produce different physiological patterns for innocent vs. guilty subjects.

The CTF represents one of the most extensively researched approaches in the polygraph discipline. It is the primary testing methodology described in the Federal Psychophysiological Detection of Deception Examiner Handbook, published in Polygraph journal volume 40(1) [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Confirms the MGQT, ZCT, You-Phase ZCT protocols, inter-question timing guidelines, and scoring procedures used in federal polygraph programs. The National Center for Credibility Assessment (NCCA) — formerly the Department of Defense Polygraph Institute (DoDPI) — is the federal institution responsible for training government polygraph examiners, and CTF methodology is a core component of its curriculum [2]Verified NCCA: The National Center for Credibility Assessment
Confirms the NCCA as the federal training center for government polygraph examiners, formerly DoDPI and DACA. The largest meta-analysis ever conducted on the Comparison Question Test, analyzing 138 datasets, found a meta-analytic effect size of 0.69 including inconclusives, with motivation level showing a positive linear relationship with accuracy, and no publication bias was detected [3]Verified A Comprehensive Meta-Analysis of the Comparison Question Polygraph Test
Confirms meta-analytic effect size of 0.69 from 138 datasets, positive motivation-accuracy relationship, and no publication bias detected.

Historical Context and Development

The comparison question approach traces its origins to the work of John E. Reid. In 1947, Reid published "A Revised Questioning Technique in Lie-Detection Tests" in the Journal of Criminal Law and Criminology, introducing the concept of using "comparative response" and "guilt complex" questions alongside relevant questions in polygraph examinations [9]Verified Reid Method: Developing Probable Lie Comparison Questions
Confirms John Reid developed the probable lie comparison question in 1947 as one of the most significant developments in polygraph testing. Before Reid's innovation, polygraph testing relied primarily on the Relevant-Irrelevant (R-I) test, which simply compared responses to relevant questions against neutral, irrelevant questions. The R-I test suffered from a significant limitation: there was no way to distinguish physiological arousal caused by the emotional impact of being asked about a crime from arousal specifically related to deception.

Reid's contribution — the probable-lie comparison (PLC) question — is considered one of the most significant developments in polygraph testing [9]Verified Reid Method: Developing Probable Lie Comparison Questions
Confirms John Reid developed the probable lie comparison question in 1947 as one of the most significant developments in polygraph testing. The comparison question served as an internal control mechanism: if a truthful examinee was concerned about the broader moral questions raised by comparison items, their physiological responses to those questions would exceed their responses to the relevant questions. Conversely, a deceptive examinee focused on the relevant questions would show greater reactivity there.

In 1960, Cleve Backster introduced the Zone Comparison Technique (ZCT), building upon Reid's work [10]Verified Backster and Federal Scoring Compared / Backster Zone Comparison Technique Documentation
Confirms Backster developed the first numerical scoring system, ZCT circa 1960, and the Federal You-Phase scoring methodology. Backster also introduced numerical scoring systems for chart analysis around 1959, allowing for more objective evaluation of polygraph data [10]Verified Backster and Federal Scoring Compared / Backster Zone Comparison Technique Documentation
Confirms Backster developed the first numerical scoring system, ZCT circa 1960, and the Federal You-Phase scoring methodology. His concepts of anticlimax dampening, psychological set, zones, spots, and 7-position scoring revolutionized the profession [10]Verified Backster and Federal Scoring Compared / Backster Zone Comparison Technique Documentation
Confirms Backster developed the first numerical scoring system, ZCT circa 1960, and the Federal You-Phase scoring methodology. Backster published the foundational 'Standardized Polygraph Notepack and Technique Guide: Backster Zone Comparison Technique' in 1963, providing the first highly standardized rationale and structure for the administration and scoring of a comparison question technique [11]Verified Standardized Polygraph Notepack and Technique Guide: Backster Zone Comparison Technique
Confirms the 1963 foundational documentation of the Zone Comparison Test methodology by Cleve Backster. The federal government subsequently standardized comparison testing through the MGQT format, incorporating elements from various comparison question approaches while adding specific protocols for data collection, scoring, and quality assurance.

Primary Applications of CTF

Comparison Test Formats are employed across a wide spectrum of high-stakes assessment contexts:

Criminal Investigations: CTF is the standard technique for specific-issue criminal investigations, where law enforcement agencies assess whether a suspect, witness, or person of interest is being truthful about involvement in or knowledge of a specific criminal act.

National Security Screenings: Federal agencies including the CIA, NSA, and Department of Defense use CTF-based examinations — along with the Test for Espionage and Sabotage (TES) and Counterintelligence Scope Polygraph (CSP) — for personnel vetting [12]Verified A Comparison of PDD Accuracy Rates: CISP vs. TES Question Formats
Confirms comparison of two screening test formats used in U.S. intelligence community with significant detection rates. Research comparing the CSP and TES formats found significant differences in sensitivity and specificity profiles between these screening approaches [12]Verified A Comparison of PDD Accuracy Rates: CISP vs. TES Question Formats
Confirms comparison of two screening test formats used in U.S. intelligence community with significant detection rates.

Personnel Pre-Employment Screening: Federal law enforcement agencies use CTF protocols as part of pre-employment polygraph testing programs to assess applicant suitability and integrity. Learn more about how to find the best lie detector test service.

Legal and Evidentiary Testing: In jurisdictions where polygraph results may be considered as evidence, CTF examinations conducted under strict evidentiary protocols provide a standardized and defensible methodology. APA Standards require that evidentiary techniques demonstrate an unweighted average accuracy rate of 90% or greater [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

Post-Conviction Monitoring: Adapted versions of CTF are used in PCSOT programs, where convicted sex offenders are monitored through regular polygraph examinations as part of supervision conditions.

Modified General Question Test (MGQT)

The Modified General Question Test (MGQT) is the primary comparison test format used in federal polygraph examinations. It represents the U.S. government's standardized approach to criminal-specific and issue-specific polygraph testing, as described in the Federal Psychophysiological Detection of Deception Examiner Handbook [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Confirms the MGQT, ZCT, You-Phase ZCT protocols, inter-question timing guidelines, and scoring procedures used in federal polygraph programs.

The MGQT typically employs a question sequence beginning with an irrelevant question to establish physiological baseline conditions, followed by a carefully structured alternation of relevant, comparison, and sacrifice relevant questions. A standard MGQT examination includes between two and five relevant questions addressing the core issues under investigation. These are interspersed with two to four comparison questions — either probable-lie or directed-lie format — and one or more sacrifice relevant questions. The Air Force Modified General Question Test (AFMGQT) is one of the APA-validated testing methods that follows this structure [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

One defining characteristic of the MGQT is its requirement that relevant questions be "bracketed" by comparison questions in at least one chart during data collection. The Federal You-Phase format always scores relevant question tracings against the stronger bracketing comparison question tracings [10]Verified Backster and Federal Scoring Compared / Backster Zone Comparison Technique Documentation
Confirms Backster developed the first numerical scoring system, ZCT circa 1960, and the Federal You-Phase scoring methodology. This bracketing ensures that every relevant question is immediately preceded and followed by a comparison question, creating a rigorous comparison framework that minimizes positional effects.

Zone Comparison Test (ZCT)

The Zone Comparison Test (ZCT), developed by Cleve Backster around 1960, is a major CTF variant widely used in both government and private sector polygraph testing [10]Verified Backster and Federal Scoring Compared / Backster Zone Comparison Technique Documentation
Confirms Backster developed the first numerical scoring system, ZCT circa 1960, and the Federal You-Phase scoring methodology. The ZCT was the first modern PDD technique in general use to incorporate numerical analysis and was adopted by the U.S. Army Military Police School (USAMPS) in 1961 [10]Verified Backster and Federal Scoring Compared / Backster Zone Comparison Technique Documentation
Confirms Backster developed the first numerical scoring system, ZCT circa 1960, and the Federal You-Phase scoring methodology.

The ZCT organizes questions into distinct "zones" — pairs of comparison and relevant questions analyzed as units. In a typical ZCT structure, each zone contains one comparison question followed by one relevant question, with three TDA (test data analysis) spots in the standard ZCT format and two TDA spots in the You-Phase variant. The examiner evaluates whether the physiological response to the comparison question exceeds, equals, or is less than the response to the relevant question within each zone.

A significant theoretical contribution of the ZCT is Backster's concept of anticlimax dampening, which posits that an individual's physiological reactions will be dominated by whatever stimulus represents the greatest perceived threat [10]Verified Backster and Federal Scoring Compared / Backster Zone Comparison Technique Documentation
Confirms Backster developed the first numerical scoring system, ZCT circa 1960, and the Federal You-Phase scoring methodology. For a deceptive examinee, the relevant questions constitute the greatest threat, "dampening" their reactivity to comparison questions. For a truthful examinee, the comparison questions represent the greater concern. This theory provides a psychological framework for understanding why the comparison methodology works, and research on the psychological and physiological foundations of polygraph testing has further validated these principles.

You-Phase Zone Comparison Test

The You-Phase Zone Comparison Test is a variant of the standard ZCT that modifies the construction and delivery of comparison questions. In the You-Phase format, comparison questions are framed using second-person phrasing. Two versions of the You-Phase technique exist today: the U.S. Federal You-Phase format, taught by the Department of Defense, and the version originally developed by Backster in 1963 [11]Verified Standardized Polygraph Notepack and Technique Guide: Backster Zone Comparison Technique
Confirms the 1963 foundational documentation of the Zone Comparison Test methodology by Cleve Backster.

The You-Phase ZCT was also designed by Backster, and the version adopted by the federal Polygraph Examiner's Guide is the one taught at NCCA [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Confirms the MGQT, ZCT, You-Phase ZCT protocols, inter-question timing guidelines, and scoring procedures used in federal polygraph programs. This format was developed to address certain limitations in the standard ZCT's comparison question formulation. By making comparison questions more personally relevant, the You-Phase approach aims to ensure that truthful examinees produce robust physiological responses to comparison items, thereby reducing the risk of false positive outcomes.

Research comparing field study data from different comparison question types has provided evidence for the practical effectiveness of both exclusive and non-exclusive comparison questions in operational settings [8]Verified Examining Different Types of Comparison Questions in a Field Study of CQT Polygraph Technique
Confirms field study evidence for the practical effectiveness of both exclusive and non-exclusive comparison questions.

Matte Quadri-Track Zone Comparison Test

The Matte Quadri-Track Zone Comparison Test (MQTZCT), first described by James Allan Matte in a 1978 publication in the Polygraph journal, expands on traditional zone comparison methodology by incorporating a fourth "track" of questions designed to assess the examinee's fear of an error by the polygraph instrument [10]Verified Backster and Federal Scoring Compared / Backster Zone Comparison Technique Documentation
Confirms Backster developed the first numerical scoring system, ZCT circa 1960, and the Federal You-Phase scoring methodology.

This additional track addresses a potential confounding variable: an examinee who is truthful but intensely afraid of being falsely accused may produce elevated responses to relevant questions not because of deception, but because of fear of consequences from a wrong result. The MQTZCT includes "Inside Track" questions that directly assess whether the examinee is afraid the instrument will make a mistake on the relevant questions. By measuring this fear separately, the examiner can factor it into the analysis and potentially reduce false positive outcomes attributable to test anxiety rather than actual deception. Understanding calming techniques for polygraph examinations can help examinees manage this type of anxiety.

Relevant Questions

Relevant questions address the specific issue under investigation directly. They are the core questions around which the entire examination is built. Examples include: "Did you steal that car from the parking lot?" or "Did you disclose classified information to an unauthorized person?"

A deceptive individual is expected to produce a significantly stronger physiological response to relevant questions because they represent the greatest psychological threat. Relevant questions must be clear, unambiguous, and focused on a single issue to ensure valid physiological measurement. Typically, an MGQT examination includes two to five relevant questions. In the ZCT format, primary relevant questions (R5 and R7) test direct involvement, while a secondary relevant question (R10) tests secondary involvement [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Confirms the MGQT, ZCT, You-Phase ZCT protocols, inter-question timing guidelines, and scoring procedures used in federal polygraph programs.

Comparison Questions (Probable-Lie)

Also known as Probable-Lie Comparison Questions (PLCQs), these questions address broad categories of past behavior similar in nature to the relevant issue but deliberately separated from it in time or scope. For example: "Before 2015, did you ever steal anything of value?"

The PLC question was developed by John Reid in 1947 and is defined as "a question regarding a past act of wrongdoing of the same general nature as the relevant incident under investigation, to which the subject will probably lie or be doubtful as to accuracy of the answer" [9]Verified Reid Method: Developing Probable Lie Comparison Questions
Confirms John Reid developed the probable lie comparison question in 1947 as one of the most significant developments in polygraph testing. A truthful examinee, having nothing to hide regarding the relevant questions, focuses concern on these broader questions, producing greater physiological responses to them. A deceptive examinee, focused on the relevant questions, shows relatively suppressed responses to comparison items.

Reid's original PLCQ was later labeled the Non-Exclusive Control Question (NECQ), which Backster subsequently refined into the Exclusive Control Question (ECQ) [8]Verified Examining Different Types of Comparison Questions in a Field Study of CQT Polygraph Technique
Confirms field study evidence for the practical effectiveness of both exclusive and non-exclusive comparison questions. The time-barring element ensures the comparison question does not overlap with the relevant issue under investigation.

Directed-Lie Comparison Questions

Directed-Lie Comparison Questions (DLCQs) represent an alternative approach to comparison questioning that has been in use by some government agencies since the late 1960s [8]Verified Examining Different Types of Comparison Questions in a Field Study of CQT Polygraph Technique
Confirms field study evidence for the practical effectiveness of both exclusive and non-exclusive comparison questions. Instead of relying on the probability that the examinee will be deceptive about broad past behaviors, the examiner explicitly instructs the examinee to answer "No" to a question where the truthful answer is clearly "Yes." For example: "Did you ever tell a lie to someone who trusted you?"

The advantage of directed lies is standardization — the examiner knows with certainty that the examinee is lying on these items, providing a known deceptive baseline. DLCQs can be standardized more easily than PLCs, they are less intrusive, and their effectiveness is less subject to examiner skill [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards. Research has consistently shown little meaningful difference in effect size between DLCQs and PLCQs [8]Verified Examining Different Types of Comparison Questions in a Field Study of CQT Polygraph Technique
Confirms field study evidence for the practical effectiveness of both exclusive and non-exclusive comparison questions, and the Directed Lie Screening Test (DLST) uses a repeated series of two relevant and two directed-lie comparison questions with the conventional 7-position scoring system.

Sacrifice Relevant Questions

Sacrifice relevant questions serve a preparatory function within the test question sequence. They introduce the relevant topic without directly addressing the specific allegation. For example: "Regarding the theft of the car, do you intend to answer each question truthfully?"

This question type helps the examinee transition psychologically into the subject matter and "absorbs" the initial orienting response that naturally occurs when a sensitive topic is first introduced. By including a sacrifice relevant question early in the sequence, the examiner ensures that subsequent scored relevant questions are not artificially elevated by novelty or surprise effects. Sacrifice relevant questions are not scored in the numerical analysis.

Irrelevant Questions

Irrelevant questions are neutral, factual items completely unrelated to the investigation. Examples include: "Are you now in Alabama?" or "Is today Tuesday?" These questions are designed to elicit no emotional or psychological reaction and establish the examinee's physiological baseline — the normal resting state of their autonomic nervous system activity.

The first question in a chart is typically an irrelevant question, which also serves to absorb the physiological artifact associated with the start of data collection. Irrelevant questions are not scored but are essential for interpreting physiological data from the scored question categories.

Fundamental Rules for Effective CTF Questions

The validity and reliability of any CTF examination depend critically on the quality of question construction. Poorly worded, ambiguous, or improperly scoped questions can compromise the entire examination by introducing physiological noise that confounds the comparison analysis.

Several fundamental principles guide CTF question construction:

Single-Issue Focus: Each relevant question should address only one discrete issue or behavior. Compound questions that address multiple issues create interpretive ambiguity because a physiological response cannot be attributed to a specific element of a multi-part question.

Clarity and Simplicity: Questions should use straightforward language at an appropriate reading level. Technical jargon, legalistic phrasing, and complex sentence structures should be avoided. The examinee must understand the precise meaning of every question.

Yes/No Answer Format: All CTF questions require simple "yes" or "no" answers. Open-ended questions are not compatible with polygraph testing because physiological measurement occurs during and immediately after question delivery and answer.

Time Separation for Comparison Questions: Probable-lie comparison questions must be clearly separated in time from the relevant issue. If the relevant question asks about an event in 2020, the comparison question should reference a period such as "Before 2015."

Behavioral Parallel: Comparison questions should address a category of behavior psychologically similar to but distinct from the relevant issue. For a theft investigation, a comparison question about past dishonesty or stealing is appropriate.

The Art of Comparison Question Development

Developing effective comparison questions is often considered the most challenging aspect of CTF examination preparation. The comparison question must walk a fine line: broad enough that virtually anyone would feel concern about it, yet specific enough to generate genuine psychological engagement.

Field research has demonstrated the practical effectiveness of both exclusive and non-exclusive comparison questions in operational settings [8]Verified Examining Different Types of Comparison Questions in a Field Study of CQT Polygraph Technique
Confirms field study evidence for the practical effectiveness of both exclusive and non-exclusive comparison questions. If the comparison question is too mild, even truthful examinees may not produce sufficient physiological responses, potentially leading to false positive outcomes. If too strong or closely related to the relevant issue, it may overwhelm relevant question responses.

Experienced examiners develop comparison questions through a combination of structured protocols and clinical judgment refined through years of practice. The pretest interview provides valuable information about the examinee's background, values, and concerns that can inform comparison question development. For an in-depth look at effective pretest strategies, see our guide on building examiner-examinee rapport.

Research by Charles Robert Honts demonstrated that between-chart discussion of comparison questions significantly improved CQT accuracy, and this procedural refinement has become standard practice in modern CQT administration [6]Verified The Discussion of Comparison Questions Between List Repetitions Is Associated with Increased Test Accuracy
Confirms that between-chart discussion of comparison questions significantly improved CQT accuracy.

Why the Pretest Is Critical to CTF Success

The pretest phase is arguably as important as the in-test data collection itself. During this phase, the examiner accomplishes several critical objectives:

Informed Consent and Orientation: The examiner explains the polygraph process, the types of questions to be asked, and the physiological measurements involved. All questions are reviewed with the examinee prior to the collection of test data [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Confirms the MGQT, ZCT, You-Phase ZCT protocols, inter-question timing guidelines, and scoring procedures used in federal polygraph programs.

Question Review and Agreement: Every question is presented to the examinee before data collection begins. The examiner ensures the examinee understands the precise meaning of each question and agrees on the wording. This process eliminates ambiguity that could confound the physiological data.

Comparison Question Development: Through skilled interviewing, the examiner gauges the examinee's personality, communication style, and areas of sensitivity — all informing final question wording. Understanding what behavior a polygraph examiner looks for during this phase is essential for new practitioners.

Acquaintance Test Administration: APA Standards require examiners to conduct an acquaintance test for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards. The acquaintance test familiarizes the examinee with test procedures, helps set instrument gains and centerings, helps detect countermeasures, and assesses responsiveness range.

Chart Collection Procedures

During the data collection phase, the examiner presents the reviewed questions while recording physiological data across multiple channels. The polygraph instrument simultaneously records respiration patterns (thoracic and abdominal, recorded separately using two pneumograph components), electrodermal activity (EDA/skin conductance), cardiovascular measures including blood pressure and pulse rate, and in many protocols, peripheral vasomotor activity via finger plethysmograph [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

Examiners collect a minimum of three charts, with many protocols requiring three to five chart presentations. Each chart presents the full question sequence, allowing for repeated measurement of physiological responses to each question across multiple presentations. The consistency of responses across charts is a critical factor in decision making — research has demonstrated that chart repetitions are essential for ensuring that outcomes are not merely due to chance [6]Verified The Discussion of Comparison Questions Between List Repetitions Is Associated with Increased Test Accuracy
Confirms that between-chart discussion of comparison questions significantly improved CQT accuracy.

Question positions may be rotated between charts to control for order effects. The examiner pairs the strongest-responding questions for analysis, ensuring that scoring captures the most meaningful physiological comparisons.

Inter-Question Timing and Technical Parameters

According to APA Standards of Practice, questions used in the assessment of truth and deception shall be followed by time intervals of not less than 20 seconds from question onset to question onset [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards. The federal Polygraph Law Enforcement Pre-Employment Assessment (PLEA) guide specifies a question spacing of 15 to 25 seconds from onset of applied stimulus [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Confirms the MGQT, ZCT, You-Phase ZCT protocols, inter-question timing guidelines, and scoring procedures used in federal polygraph programs. In practice, experienced examiners typically maintain intervals of approximately 20 to 25 seconds, allowing sufficient time for physiological responses to develop and return toward baseline before the next stimulus.

Proper timing is essential for clean data collection. Insufficient inter-question intervals can cause physiological responses to overlap, making it difficult to attribute reactions to specific questions. Understanding suppression responses in polygraph testing helps examiners identify when interval adjustments may be needed.

Modern digital polygraph systems record data at sampling rates of not less than 25 samples per second, as specified by the APA Standard for Polygraph Instrumentation [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards. Audio and video recording of all phases of the examination is required under APA Standards.

The 7-Position Scoring Scale

The 7-position numerical scoring scale is the standard method for evaluating CTF polygraph data. For each physiological channel — respiration, electrodermal activity, relative blood pressure (cardiograph), and peripheral vasomotor activity — a score from +3 to -3 is assigned for each presentation of a relevant question [13]Verified The Utah Numerical Scoring System
Confirms the 7-position scoring scale with scores from +3 to -3 across respiration, EDA, cardiograph, and plethysmograph channels. The response to each relevant question is compared to the response to a nearby comparison question.

A positive score is assigned when the psychophysiological reaction is greater to the comparison question than to the relevant question, a negative score when the reaction is greater to the relevant question, and a zero when responses are approximately equal [13]Verified The Utah Numerical Scoring System
Confirms the 7-position scoring scale with scores from +3 to -3 across respiration, EDA, cardiograph, and plethysmograph channels. The 7-position scale is loosely based on the psychometric scales developed by Rensis Likert and is sometimes referred to as a semi-objective scoring system [13]Verified The Utah Numerical Scoring System
Confirms the 7-position scoring scale with scores from +3 to -3 across respiration, EDA, cardiograph, and plethysmograph channels.

For a comprehensive exploration of this scoring methodology, see our detailed guide to the 7-position scale in polygraph testing. The NCCA (formerly DACA) supports the use of the seven-position scale exclusively [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Confirms the MGQT, ZCT, You-Phase ZCT protocols, inter-question timing guidelines, and scoring procedures used in federal polygraph programs. Scores of +/-3 are rarely assigned in practice, typically reserved for the most extreme and unambiguous response differentials [13]Verified The Utah Numerical Scoring System
Confirms the 7-position scoring scale with scores from +3 to -3 across respiration, EDA, cardiograph, and plethysmograph channels.

The development of automated scoring in modern polygraph analysis has complemented manual scoring, though the APA maintains that hand-scoring by the examiner remains the primary method.

Scoring Rules and Computation

Scoring systems have three common components: scoring rules, computation rules, and decision rules (cut scores) [13]Verified The Utah Numerical Scoring System
Confirms the 7-position scoring scale with scores from +3 to -3 across respiration, EDA, cardiograph, and plethysmograph channels. Scoring rules relate to the choice of tracing features, rejection of artifacts, and how question pairs are compared and numbers assigned. Computation rules describe the weight and how numbers are combined. Decision rules — or cut scores — govern the relationship between computation rules and the examiner's categorical decision.

Backster was the first to apply a positive and negative scoring system comparing relevant questions against comparison questions [10]Verified Backster and Federal Scoring Compared / Backster Zone Comparison Technique Documentation
Confirms Backster developed the first numerical scoring system, ZCT circa 1960, and the Federal You-Phase scoring methodology. His numerical scoring technique has been modified for Federal and Utah polygraph examinations. The Federal You-Phase always scores relevant question tracings against the stronger bracketing comparison question, while the Backster You-Phase uses the Either-Or Rule (EOR) to select the bracketing comparison tracing [10]Verified Backster and Federal Scoring Compared / Backster Zone Comparison Technique Documentation
Confirms Backster developed the first numerical scoring system, ZCT circa 1960, and the Federal You-Phase scoring methodology.

The Utah Numerical Scoring System, detailed by Bell, Raskin, Honts, and Kircher (1999), formalized decision rules for specific-incident comparison question tests and has been extensively validated [4]Verified Meta-Analysis of the Comparison Question Test
Confirms the first meta-analysis of the CQT found significant moderator effects for subject type, incentives, and decision policy.

Three Decision Outcomes

After numerical scoring is complete, examiners render one of three possible opinions for specific-issue examinations:

No Deception Indicated (NDI): A favorable opinion based on test data analysis for all relevant questions in a completed test series. NDI indicates the probability of deception is within the lowest range, generally indicating truthfulness to the specific issue [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

Deception Indicated (DI): An unfavorable opinion based on test data analysis for at least one relevant question in a completed test series. DI indicates the probability of deception is in the highest range [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

No Opinion (NO): Rendered when there is insufficient physiological data for conclusive test data analysis. This may be caused by medical issues, medications, or the examinee's inability to remain still or follow instructions [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

For screening examinations, the corresponding terms are No Significant Responses (NSR), Significant Responses (SR), and No Opinion (NO) [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Confirms the MGQT, ZCT, You-Phase ZCT protocols, inter-question timing guidelines, and scoring procedures used in federal polygraph programs.

Decision Rules and Cut Scores

Multiple structured decision rules exist for translating numerical scores into categorical outcomes. Under federal evidentiary decision rules, a call of Deception Indicated (DI) is made when the total of all scores is -6 or below, or if the sum of any one relevant question is -3 or lower [15]Verified Polygraph Decision Rules for Evidentiary and Paired-Testing (Marin Protocol) Applications
Confirms DI threshold of -6 grand total or -3 per relevant question, and NDI requiring positive total scores for evidentiary rules. Decisions of No Deception Indicated (NDI) under evidentiary rules require a positive total score for each relevant question and a cumulative grand total meeting the established threshold [15]Verified Polygraph Decision Rules for Evidentiary and Paired-Testing (Marin Protocol) Applications
Confirms DI threshold of -6 grand total or -3 per relevant question, and NDI requiring positive total scores for evidentiary rules.

Six major decision rules are documented in the published literature: the Grand Total Rule (GTR), the Spot-Score Rule (SSR), the Two-Stage Rule (TSR — sometimes called the Senter Rule), and their variants [15]Verified Polygraph Decision Rules for Evidentiary and Paired-Testing (Marin Protocol) Applications
Confirms DI threshold of -6 grand total or -3 per relevant question, and NDI requiring positive total scores for evidentiary rules. The Two-Stage Rule functions by first applying the Grand Total Rule in Stage 1; if the result is inconclusive, Stage 2 applies the Spot-Score Rule for improved criterion accuracy [15]Verified Polygraph Decision Rules for Evidentiary and Paired-Testing (Marin Protocol) Applications
Confirms DI threshold of -6 grand total or -3 per relevant question, and NDI requiring positive total scores for evidentiary rules.

The selection of decision rules is typically made before conducting an examination and is most often a function of the examination type — whether diagnostic, investigative, or screening [15]Verified Polygraph Decision Rules for Evidentiary and Paired-Testing (Marin Protocol) Applications
Confirms DI threshold of -6 grand total or -3 per relevant question, and NDI requiring positive total scores for evidentiary rules. Evidentiary applications require balanced sensitivity and specificity, while investigative settings may prioritize avoiding false negatives [15]Verified Polygraph Decision Rules for Evidentiary and Paired-Testing (Marin Protocol) Applications
Confirms DI threshold of -6 grand total or -3 per relevant question, and NDI requiring positive total scores for evidentiary rules. Scoring thresholds can also be adjusted based on an agency's tolerance for error [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

Research using Between-Charts-Consistency Decision Rules on a sample of 1,000 verified scorings from the NCCA database achieved a mean decision accuracy of 87.81% (91.88% for truth-tellers and 83.40% for deceptive examinees), with an inconclusive rate of 9.8% [15]Verified Polygraph Decision Rules for Evidentiary and Paired-Testing (Marin Protocol) Applications
Confirms DI threshold of -6 grand total or -3 per relevant question, and NDI requiring positive total scores for evidentiary rules.

Meta-Analytic Evidence

The Comparison Question Test has been subjected to extensive scientific scrutiny. The largest meta-analysis ever conducted on the CQT, by Honts, Thurber, and Handler (2021), analyzed 138 datasets and found a meta-analytic effect size of 0.69 including inconclusives [3]Verified A Comprehensive Meta-Analysis of the Comparison Question Polygraph Test
Confirms meta-analytic effect size of 0.69 from 138 datasets, positive motivation-accuracy relationship, and no publication bias detected. The study found significant moderator effects, with motivation level showing a positive linear relationship with accuracy — higher-stakes testing produced better results [3]Verified A Comprehensive Meta-Analysis of the Comparison Question Polygraph Test
Confirms meta-analytic effect size of 0.69 from 138 datasets, positive motivation-accuracy relationship, and no publication bias detected. Critically, no publication bias was detected, and the results suggest that experimental studies are generalizable to real-world applications [3]Verified A Comprehensive Meta-Analysis of the Comparison Question Polygraph Test
Confirms meta-analytic effect size of 0.69 from 138 datasets, positive motivation-accuracy relationship, and no publication bias detected.

A CQT truthful outcome was found to be approximately 7 times more informative than a layperson's decision that a person is truth-telling, and a CQT deceptive outcome approximately 6 times more informative than a layperson's judgment that a person is lying [3]Verified A Comprehensive Meta-Analysis of the Comparison Question Polygraph Test
Confirms meta-analytic effect size of 0.69 from 138 datasets, positive motivation-accuracy relationship, and no publication bias detected.

Earlier meta-analytic work by Kircher, Horowitz, and Raskin (1988) — the first meta-analysis of the CQT — found significant moderator effects for subject type, incentives, and decision policy [4]Verified Meta-Analysis of the Comparison Question Test
Confirms the first meta-analysis of the CQT found significant moderator effects for subject type, incentives, and decision policy. A subsequent meta-analysis by Vrij, Mann, and Fisher (2008) found overall accuracy estimates above 85% across studies, identifying important moderator variables including examiner training and testing protocols [5]Verified A Meta-Analysis of the Comparison Question Polygraph Test: Moderator Effects
Confirms overall accuracy estimates above 85% across studies with important moderator variables identified. For a broader understanding of the spectrum of scientific studies in polygraph research, our dedicated guide provides comprehensive context.

Empirical Support for Comparison Question Mechanisms

Research has provided direct empirical evidence for the mechanisms underlying CQT effectiveness. A mock crime study with 120 participants by Horowitz, Kircher, Honts, and Raskin (1997) found that comparison questions produced different physiological patterns for innocent versus guilty subjects, providing empirical support for the CQT rationale [7]Verified The Role of Comparison Questions in Physiological Detection of Deception
Confirms mock crime study with 120 participants showing comparison questions produce different physiological patterns for innocent vs. guilty subjects.

Offe and Offe (2007) investigated the theoretical mechanisms underlying CQT effectiveness, examining the role of comparison questions in calibrating physiological responses and providing experimental evidence for the psychological processes driving accuracy [16]Verified The Comparison Question Test: Does It Work and If So How?
Confirms experimental evidence for the psychological processes driving CQT accuracy and the role of comparison questions in calibrating physiological responses. Additionally, Ginton (2017) conducted a field study comparing different types of comparison questions in real criminal investigations, providing evidence for the practical effectiveness of both exclusive and non-exclusive comparison questions [8]Verified Examining Different Types of Comparison Questions in a Field Study of CQT Polygraph Technique
Confirms field study evidence for the practical effectiveness of both exclusive and non-exclusive comparison questions.

The importance of procedural refinements has also been validated. Honts (1999) demonstrated that between-chart discussion of comparison questions significantly improved test accuracy — a finding that became standard practice in modern CQT administration [6]Verified The Discussion of Comparison Questions Between List Repetitions Is Associated with Increased Test Accuracy
Confirms that between-chart discussion of comparison questions significantly improved CQT accuracy.

Research comparing federal screening formats has also contributed to CTF validation. Studies by the DoDPI Research Division compared the Counterintelligence Scope Polygraph (CSP) and Test for Espionage and Sabotage (TES) formats, finding that both achieved significant detection rates with differences in sensitivity and specificity profiles [12]Verified A Comparison of PDD Accuracy Rates: CISP vs. TES Question Formats
Confirms comparison of two screening test formats used in U.S. intelligence community with significant detection rates [17]Verified A comparison of psychophysiological detection of deception accuracy rates obtained using the CSP and TES question formats
Confirms the CSP format had lower guilty detection rates compared to TES format, prompting evaluation of newer approaches.

APA Standards of Practice

The American Polygraph Association (APA) Standards of Practice establish comprehensive requirements for CTF examinations:

Validated Techniques: Member examiners shall use evidence-based validated testing techniques supported by research conducted in accordance with APA research standards [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

Accuracy Requirements: Evidentiary techniques must demonstrate an unweighted average accuracy rate of 90% or greater (excluding inconclusives, which shall not exceed 20%). Investigative techniques require 80% or greater accuracy [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

Inter-Question Intervals: Questions shall be followed by time intervals of not less than 20 seconds from question onset to question onset [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

Scoring Requirements: Examiner conclusions and opinions shall be based on validated scoring methods and decision rules [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

Recording: Audio and video recording of all examination phases must be maintained for a minimum of one year [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

Examination Limits: Examiners shall not conduct more than four diagnostic or three evidentiary examinations in one day, and no more than five examinations of any type in one day [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

The European Polygraph Association (EPA) maintains complementary standards for CTF examinations conducted in European jurisdictions.

Federal Examiner Handbook

The Federal Psychophysiological Detection of Deception Examiner Handbook serves as the authoritative reference for federal polygraph programs. Originally published by Counterintelligence Field Activity, it was reprinted in 2011 in the journal Polygraph, volume 40(1) [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Confirms the MGQT, ZCT, You-Phase ZCT protocols, inter-question timing guidelines, and scoring procedures used in federal polygraph programs. The handbook establishes essential elements for the conduct of the ZCT, You-Phase ZCT, MGQT, and screening formats for participating law enforcement agencies.

The NCCA's central mission is to assist federal agencies in the protection of U.S. citizens, interests, infrastructure and security by providing education and tools for credibility assessment [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards. Its responsibilities include qualifying DoD and other federal personnel for careers as PDD examiners, researching and validating credibility assessment tools, managing the Quality Assurance Program for federal polygraph standards, and providing strategic support to federal polygraph programs.

All federal polygraph examiners must be certified by the NCCA [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards. Polygraph examination types and completion dates are recorded in Scattered Castles or successor systems as required by Intelligence Community Policy Guidance (ICPG 704.6) [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards.

Directed-Lie vs. Probable-Lie Selection

The choice between directed-lie and probable-lie comparison questions remains an important practical consideration for CTF examiners. While Raskin introduced the Directed Lie Control Question in the 1980s [8]Verified Examining Different Types of Comparison Questions in a Field Study of CQT Polygraph Technique
Confirms field study evidence for the practical effectiveness of both exclusive and non-exclusive comparison questions, the consensus of published research has trended toward the conclusion that there is little, if any, real difference in effect size between DLCQs and PLCQs [8]Verified Examining Different Types of Comparison Questions in a Field Study of CQT Polygraph Technique
Confirms field study evidence for the practical effectiveness of both exclusive and non-exclusive comparison questions.

DLCQs offer several practical advantages: greater standardization, less dependence on examiner skill in question development, easier explanation in legal settings, and transparency about the comparison mechanism. PLCQs, when skillfully developed, may offer stronger psychological engagement for certain examinees. Examiners using the Reid Examination Technique for PLC development must have exceptional analytical, interviewing, listening, and discernment skills [9]Verified Reid Method: Developing Probable Lie Comparison Questions
Confirms John Reid developed the probable lie comparison question in 1947 as one of the most significant developments in polygraph testing.

The key principle is that whatever comparison question type is used, the manner in which it is introduced to the examinee during the pretest is crucial to effectiveness [8]Verified Examining Different Types of Comparison Questions in a Field Study of CQT Polygraph Technique
Confirms field study evidence for the practical effectiveness of both exclusive and non-exclusive comparison questions. This underscores the importance of thorough examiner training and mastery of pretest interviewing skills.

Countermeasure Detection and Chart Interpretation

Since breathing is more readily controlled than other physiological activity recorded with the polygraph, it is one of the first areas examiners look for indications of countermeasures [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards. Indicators include paced breathing, holding one's breath, very slow breathing, irregularly shaped waveforms, hyperventilation, and tactical use of deep breaths.

Modern polygraph instrumentation includes activity sensors (motion sensors) that monitor body movements to help differentiate reactions caused by physical issues from those caused by psychophysiological responses [14]Verified APA Standards of Practice
Confirms minimum 20-second inter-question intervals, validated technique requirements, accuracy standards, recording requirements, and scoring standards. A seat activity sensor provides an additional data channel for identifying movement artifacts.

For examinees, understanding these monitoring capabilities can be reassuring. Our guide on why guilty individuals might take a lie detector test explores the psychology of deceptive examinees, while statement analysis techniques can complement polygraph findings in comprehensive investigations.