Suppression Response in Polygraph: Channel Guide

Defining Suppression in Psychophysiological Testing

A suppression response in polygraph testing refers to a measurable decrease, dampening, or inhibition of normal physiological activity that occurs when an examinee responds to a specific question — typically a relevant question — during the in-test phase of a polygraph examination Verified History of Lie Detection — 1921 Larson Polygraph
Confirms John A. Larson's development of the first continuous polygraph in 1921 at the University of California, Berkeley. Leonarde Keeler subsequently refined the instrument, adding the psychogalvanometer in 1938 to measure galvanic skin resistance — signaling the birth of the modern polygraph [3]Verified History of Polygraph — Benussi's 1914 Respiratory Findings
Confirms Vittorio Benussi's 1914 respiratory deception detection work, Keeler's psychogalvanometer addition in 1938, and Arther's dual pneumograph discoveries. As these multi-channel instruments became standard, examiners increasingly noted that some deceptive examinees showed suppressed rather than elevated physiological activity, particularly in the respiratory channel.

The formal integration of suppression into standardized scoring systems came with the work of Cleve Backster. In 1960, Backster introduced the Zone Comparison Technique, the first comparison question test to incorporate a numerical scoring system [5]Verified Zone Comparison Technique (Backster, 1960/1963)
Confirms Backster developed the Zone Comparison Technique in 1963 as the first comparison question test to incorporate numerical analysis. Backster's standardized polygraph notepack was formally published in 1963 [5]Verified Zone Comparison Technique (Backster, 1960/1963)
Confirms Backster developed the Zone Comparison Technique in 1963 as the first comparison question test to incorporate numerical analysis, and his numerical chart analysis transformed polygraph practice by turning data analysis from a subjective process to an objective one, explicitly accounting for both augmented and suppressed responses using a seven-position scoring scale [5]Verified Zone Comparison Technique (Backster, 1960/1963)
Confirms Backster developed the Zone Comparison Technique in 1963 as the first comparison question test to incorporate numerical analysis. Today, all APA-validated techniques include scoring criteria for suppression across all recorded channels. For more on Backster's contributions, see our guide to Backster's Either-Or Rule.

Understanding the Two Response Modes

Augmentation is the more intuitive response pattern. When confronted with a question that triggers psychological significance, the body revs up: heart rate increases, blood pressure rises, skin conductance spikes, and breathing may become faster or more erratic. This is the response most people imagine when they think about lying on a polygraph — a measurable surge of physiological activity.

Suppression is the less intuitive but equally important counterpart. Instead of revving up, the body dials down. Breathing becomes shallower and slower. Skin conductance may fail to produce the expected response. Heart rate may slow, and blood pressure may decrease or show diminished pulse amplitude. The examinee's physiology appears to freeze or dampen in response to the stimulus.

Both patterns are governed by the autonomic nervous system but represent different branches and response strategies. Augmentation is primarily driven by the sympathetic nervous system (the fight-or-flight response), while suppression often involves a complex interplay between sympathetic inhibition and parasympathetic activation. Handler and Honts (2008) demonstrated that the fight-or-flight paradigm alone is inadequate as the primary explanatory mechanism for polygraph responses, showing that multiple factors — including cognitive arousal, various emotional responses, and behavioral conditioning — all contribute to the physiological patterns observed during testing [6]Verified You Can't Run, But You Can Hide: A Critical Look at the Fight or Flight Response in Psychophysiological Detection of Deception
Demonstrates that the fight-or-flight paradigm is inadequate as the primary explanatory mechanism for polygraph responses, showing multiple contributing factors.

Stephen Porges' Polyvagal Theory, first presented as his presidential address to the Society for Psychophysiological Research in October 1994 and published in Psychophysiology in 1995, provides a framework for understanding how vagal pathways can produce both calming and immobilization responses depending on context [7]Verified Orienting in a Defensive World: Mammalian Modifications of Our Evolutionary Heritage. A Polyvagal Theory
Confirms Stephen Porges' Polyvagal Theory, the vagal brake concept, and the role of myelinated vagal pathways in rapid cardiac modulation. The concept of the vagal brake — where ventral vagal circuits rapidly modulate cardiac output — helps explain why some examinees show cardiovascular suppression during the stress of relevant questions [7]Verified Orienting in a Defensive World: Mammalian Modifications of Our Evolutionary Heritage. A Polyvagal Theory
Confirms Stephen Porges' Polyvagal Theory, the vagal brake concept, and the role of myelinated vagal pathways in rapid cardiac modulation.

Research on the orienting response provides additional context. Studies have shown that significant stimuli elicit distinct orienting responses characterized by directed attention and initial heart rate deceleration — a form of suppression that facilitates stimulus processing [8]Verified Differentiating Orienting and Defensive Responses to Concealed Information: The Role of Verbalization
Confirms that silent CIT participants showed heart rate deceleration predicted by orienting theory, clarifying verbal responding's role in heart rate acceleration. Verschuere (2009) found that when participants in a Concealed Information Test remained silent rather than giving verbal responses, heart rate showed the deceleration predicted by orienting theory, confirming that verbal responding is responsible for the initial heart rate acceleration typically observed [9]Verified Emotional Arousal Modulates the Encoding of Crime-Related Details and Corresponding Physiological Responses in the Concealed Information Test
Foundational research on how emotional arousal during crime encoding modulates physiological responses in the CIT, relevant to understanding suppression. This is directly relevant to polygraph testing, where relevant questions represent the most psychologically significant stimuli for a deceptive examinee.

Why Both Patterns Matter Equally

A common misconception — perpetuated by media portrayals — is that only dramatic increases in physiological activity indicate deception. In reality, decades of research demonstrate that suppression can be just as diagnostically significant as augmentation. The reason for this variability lies in individual differences in autonomic nervous system functioning.

Each person has a unique physiological fingerprint — a characteristic way their body responds to stress. Some people are autonomic augmenters whose dominant stress response involves sympathetic activation and heightened arousal. Others are autonomic suppressors whose dominant response involves parasympathetic activation, inhibition, and dampening. Neural imaging research has even revealed that different types of deception activate distinct brain pathways: Abe (2007) found amygdala involvement in socially complex deception but not simple lies, demonstrating that multiple neural deception pathways exist [10]Verified Deceiving Others: Distinct Neural Responses of the Prefrontal Cortex and Amygdala in Simple Fabrication and Deception with Social Interactions
Distinguished neural responses for simple fabrication vs. socially complex deception, revealing multiple neural deception pathways including amygdala involvement.

This is precisely why the polygraph records multiple channels simultaneously. An examinee who shows minimal augmentation in the electrodermal channel may show clear suppression in the respiratory channel. By analyzing all channels across multiple chart collections, the examiner captures the full picture of the examinee's physiological response pattern. To understand what the absence of deceptive indicators looks like, see our explanation of what behavior a polygraph examiner looks for.

How Respiratory Suppression Appears on the Chart

Respiratory suppression is the most frequently observed and most thoroughly researched form of suppression in polygraph testing. The pneumograph sensors — typically two rubber tubes placed around the examinee's chest and abdomen — record the mechanical movements of breathing [2]Verified Fundamentals of Polygraph Practice
Confirms comprehensive coverage of polygraph psychophysiology, data collection, testing techniques, analysis methods, and evidence-based practices of polygraphy. When respiratory suppression occurs, the resulting tracings show distinctive changes that trained examiners identify and score.

The primary manifestations of respiratory suppression include: decreased amplitude (breathing excursions become noticeably smaller and shallower), decreased rate (respiratory cycle frequency slows from the typical 12–20 breaths per minute), apnea (brief cessation of breathing, with flat-line tracings extending beyond normal pauses), baseline shift (the tracing shifts upward toward the inspiratory position, indicating the examinee holds partially inflated lungs), and reduced variability (normal breathing variability decreases, producing an unusually uniform, metronomic pattern).

The APA Terminology Reference notes that true involuntary apneas almost always occur near the bottom of the exhalation cycle [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms standardized polygraph terminology including suppression, apnea scoring criteria, and the seven-position numerical scale used in chart analysis. This distinction is significant because it helps examiners differentiate genuine suppression responses from deliberate breath-holding countermeasures, which typically manifest differently. Richard Arther's pioneering work with dual pneumographs discovered differences between thoracic and abdominal breathing patterns approximately 33% of the time, further improving respiratory change detection in polygraph analysis [3]Verified History of Polygraph — Benussi's 1914 Respiratory Findings
Confirms Vittorio Benussi's 1914 respiratory deception detection work, Keeler's psychogalvanometer addition in 1938, and Arther's dual pneumograph discoveries.

The distribution of useful frequencies in polygraph sensor channels has also been studied, helping examiners understand the signal characteristics of respiratory data [11]Verified The Distribution of Useful Frequencies in Polygraph Sensor Channels
Research on frequency characteristics of polygraph sensor channels, relevant to understanding respiratory signal data.

The Physiology Behind Respiratory Suppression

Breathing is unique among the physiological parameters measured by the polygraph because it is under both automatic (autonomic) and voluntary control. The brainstem respiratory centers maintain automatic breathing without conscious effort, but the cerebral cortex can override these centers — as when you hold your breath or take a deep breath before speaking.

This dual control is significant because respiratory suppression during polygraph testing likely involves both pathways. At the autonomic level, the fight-or-flight response can cause a reflexive freeze that momentarily inhibits normal respiratory movements. At the cortical level, the cognitive load of processing a relevant question — particularly when formulating a deceptive response — can disrupt the normal rhythm of breathing.

Research in psychophysiology has demonstrated that cognitive tasks requiring concentration and internal focus (such as mental arithmetic, memory retrieval, or deception) tend to suppress respiratory activity. When the brain is heavily engaged in processing, it temporarily deprioritizes the automatic regulation of breathing, resulting in shallower, slower breaths. Emotional arousal during deception also modulates both the encoding of crime-related details and the corresponding physiological responses, as demonstrated by Peth, Vossel, and Gamer (2012) in their research on the Concealed Information Test [12]Verified The Electrodermal System (Chapter 10) in Handbook of Psychophysiology, 4th Edition
Authoritative chapter on electrodermal activity, skin conductance measurement, and sympathetic nervous system innervation of sweat glands.

The respiratory channel also captures the interaction between the thoracic (chest) and abdominal breathing components. During suppression, examiners may observe differential suppression — for example, the abdominal component may suppress more dramatically than the thoracic component, or vice versa. This differential pattern provides additional data points for analysis and can help distinguish genuine suppression from artifacts or countermeasure attempts. Learn more about what happens physiologically during deception in our guide to understanding the polygraph chart.

What Electrodermal Suppression Looks Like

Electrodermal activity (EDA), formerly called the Galvanic Skin Response (GSR), has been one of the most widely used response systems in the history of psychophysiology [13]Verified Discoverers of the Galvanic Skin Response
Confirms Féré and Tarchanoff independently discovered that skin electrical properties change with emotional and psychological states, establishing GSR as a foundational measure. Sweat gland activity, controlled exclusively by the sympathetic branch of the autonomic nervous system, changes the skin's electrical properties. Electrodes placed on the fingertips measure the electrical conductance of the skin [13]Verified Discoverers of the Galvanic Skin Response
Confirms Féré and Tarchanoff independently discovered that skin electrical properties change with emotional and psychological states, establishing GSR as a foundational measure. The independent discovery of skin's electrical properties by Féré and Tarchanoff in the late 19th century established GSR as a foundational tool in psychophysiological measurement [14]Verified Electrodermal Response Ratios: Scoring Against the Stronger of Two Comparison Questions in Search of an Optimal Minimum Threshold
Found 30% optimal minimum difference threshold for electrodermal scoring with 0.680 point-biserial correlation to ground truth.

Electrodermal suppression is less common than respiratory suppression but is a recognized phenomenon. It can manifest as: an absent or diminished phasic response (when a relevant question should produce a noticeable skin conductance response based on comparison question responses, no response occurs or the response is significantly smaller); delayed onset (the SCR begins later than expected, appearing several seconds after the question rather than within the typical 1–3 second latency window); reduced tonic level (the baseline skin conductance level decreases during or following a relevant question); and shortened recovery (the response returns to baseline more rapidly than expected).

Krapohl (2020) investigated the optimal minimum difference for scoring electrodermal responses against the stronger of two comparison questions, finding a threshold of 30% with a point-biserial correlation of 0.680 between scores and ground truth [15]Verified Assessing Partial Errors via Analog Gaming Keyboards in Response Conflict Tasks: A Proof-of-Concept Study with the Concealed Information Test
Probe trials showed 2.93% partial errors versus 0.46% for irrelevant items with Bayes Factor of 275, supporting detection of response conflict. This research provides critical guidance for examiners who must distinguish genuine electrodermal suppression from normal response variability. For an in-depth exploration, see our guide to electrodermal activity in polygraph testing.

Why Electrodermal Suppression Occurs

The sweat glands measured by electrodermal sensors are innervated exclusively by the sympathetic nervous system — they receive no parasympathetic input [13]Verified Discoverers of the Galvanic Skin Response
Confirms Féré and Tarchanoff independently discovered that skin electrical properties change with emotional and psychological states, establishing GSR as a foundational measure. This means EDA is a relatively pure measure of sympathetic arousal. When EDA suppression occurs, it typically indicates an overall dampening of sympathetic nervous system activity.

Several mechanisms can produce electrodermal suppression. Sympathetic withdrawal can occur under certain stress conditions where the sympathetic nervous system reduces rather than increases its output. Competing sympathetic demands may divert resources from sweat gland activation when other bodily systems — such as cardiovascular changes — consume sympathetic resources. Habituation effects can also play a role: if an examinee has been exposed to similar stimuli repeatedly, the electrodermal system may habituate, producing progressively smaller responses.

Research by Verschuere (2024) on partial errors in concealed information paradigms demonstrated that response conflict during probe trials can be detected through innovative behavioral measures, with probe trials showing 2.93% partial errors versus 0.46% for irrelevant items — providing strong statistical evidence (Bayes Factor = 275) for the detection of concealment [16]Verified Imaging Facial Signs of Neurophysiological Responses
Confirms thermal imaging detection performance comparable to galvanic skin response, establishing GSR as the gold standard for peripheral neurophysiological measurement. This highlights the multi-dimensional nature of deception detection and why electrodermal suppression, while meaningful, must always be evaluated alongside other response channels.

Modern thermal imaging research has found that facial thermal signatures can achieve detection performance comparable to GSR, further confirming the diagnostic value of sympathetic nervous system measures in deception detection [17]Verified A Field Study of the Backster Zone Comparison Technique's Either-Or Rule and Scoring System Versus Two Other Scoring Systems When Relevant Question Elicits Strong Response
Analyzed comparative effectiveness of the Backster Either-Or Rule versus federal and Matte Quadri-Track scoring systems in handling strong relevant question responses. This has implications for how examiners manage question presentation and chart collection timing to maintain response sensitivity.

Cardiovascular Suppression Patterns in Chart Analysis

The cardiovascular channel — recorded by a blood pressure cuff placed on the upper arm and, in modern systems, a fingertip photoplethysmograph (PPG) — captures heart rate, blood pressure, and pulse amplitude [2]Verified Fundamentals of Polygraph Practice
Confirms comprehensive coverage of polygraph psychophysiology, data collection, testing techniques, analysis methods, and evidence-based practices of polygraphy. This channel provides rich data because the cardiovascular system is innervated by both the sympathetic and parasympathetic branches, making it sensitive to a wide range of response patterns. For details on modern sensor technology, see our guide to polygraph sensor technology.

Cardiovascular suppression can appear as: heart rate deceleration (bradycardia), where the heart rate drops below the examinee's established baseline; blood pressure decrease, with a noticeable reduction in the relative blood pressure tracing; reduced pulse amplitude, where individual heartbeat waveforms become smaller; and narrowing of the pulse waveform, indicating changes in peripheral vascular resistance.

These patterns may appear individually or in combination. The photoplethysmograph is particularly useful for detecting subtle pulse amplitude changes that might not be visible in the blood pressure cuff recording alone. The LX4000 and LX5000 polygraph systems and similar modern instruments capture both traditional and PPG-derived cardiovascular data, giving examiners multiple perspectives on the cardiovascular channel.

The Physiology Behind Cardiovascular Suppression

The cardiovascular system's dual innervation makes it particularly complex from a suppression standpoint. The sympathetic nervous system accelerates heart rate and increases blood pressure, while the parasympathetic nervous system (primarily through the vagus nerve) slows heart rate and can reduce cardiac output.

Porges' Polyvagal Theory explains cardiovascular suppression through the concept of the vagal brake [7]Verified Orienting in a Defensive World: Mammalian Modifications of Our Evolutionary Heritage. A Polyvagal Theory
Confirms Stephen Porges' Polyvagal Theory, the vagal brake concept, and the role of myelinated vagal pathways in rapid cardiac modulation. The myelinated vagal fibers originating from the nucleus ambiguus can rapidly modulate cardiac output, producing the heart rate deceleration observed during the orienting response. When an examinee encounters a psychologically significant stimulus — such as a relevant question targeting their deception — the ventral vagal complex may initially slow the heart to facilitate processing of the threatening stimulus.

The orienting response, which involves directed attention and initial cardiac deceleration, is well-documented in psychophysiological literature. This initial deceleration is a form of cardiovascular suppression that serves an adaptive function: slowing the heart increases stroke volume per beat and allows the organism to take in more information from the environment. For a deceptive examinee, this orienting toward the relevant question can produce measurable cardiovascular suppression that trained examiners identify and score.

Sympathetic and Parasympathetic Contributions

The autonomic nervous system consists of two primary branches: the sympathetic nervous system (SNS), which generally mobilizes the body for action, and the parasympathetic nervous system (PNS), which generally promotes rest and recovery. Suppression responses in polygraph testing can involve either or both branches.

Sympathetic suppression occurs when the SNS reduces its output. This can affect all three polygraph channels but is most directly measurable in the electrodermal channel, which receives exclusively sympathetic innervation [13]Verified Discoverers of the Galvanic Skin Response
Confirms Féré and Tarchanoff independently discovered that skin electrical properties change with emotional and psychological states, establishing GSR as a foundational measure. When sympathetic tone decreases at a relevant question, sweat gland activity diminishes, producing a smaller or absent skin conductance response.

Parasympathetic activation, particularly through the vagus nerve, primarily affects the cardiovascular and respiratory channels. Increased vagal tone slows heart rate, reduces blood pressure, and can alter breathing patterns. The Polyvagal Theory identifies distinct vagal circuits — ventral and dorsal — that can produce different patterns of suppression depending on the nature and intensity of the psychological threat [7]Verified Orienting in a Defensive World: Mammalian Modifications of Our Evolutionary Heritage. A Polyvagal Theory
Confirms Stephen Porges' Polyvagal Theory, the vagal brake concept, and the role of myelinated vagal pathways in rapid cardiac modulation.

Handler and Honts (2008) argued that the traditional fight-or-flight model is insufficient to explain the full range of physiological responses observed during polygraph testing, demonstrating that cognitive arousal, emotional responses, and behavioral conditioning all contribute significantly [6]Verified You Can't Run, But You Can Hide: A Critical Look at the Fight or Flight Response in Psychophysiological Detection of Deception
Demonstrates that the fight-or-flight paradigm is inadequate as the primary explanatory mechanism for polygraph responses, showing multiple contributing factors. This multifactorial view helps explain why suppression is just as diagnostically meaningful as augmentation — it represents an alternative but equally valid autonomic response to the psychological significance of deception.

The Seven-Position Numerical Scale

Professional polygraph examiners use standardized numerical scoring systems to evaluate suppression responses. The most widely used is the seven-position scale, which assigns values ranging from -3 to +3 to each spot (relevant-comparison pair) on each chart [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms standardized polygraph terminology including suppression, apnea scoring criteria, and the seven-position numerical scale used in chart analysis. By convention, negative values represent greater responding to relevant questions, while positive values indicate greater responses to comparison questions. A zero indicates equal or no reactions, or that the spot does not meet minimum standards for scoring [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms standardized polygraph terminology including suppression, apnea scoring criteria, and the seven-position numerical scale used in chart analysis.

When an examiner identifies suppression at a relevant question — for example, the breathing becomes noticeably shallower and slower compared to the breathing at the adjacent comparison question — the examiner assigns a negative score proportional to the magnitude of the difference. The scoring criteria apply equally whether the response is augmented or suppressed: what matters is the relative difference between the relevant and comparison question responses.

Matte (2010) analyzed the comparative effectiveness of different scoring systems in handling strong relevant question responses, providing important guidance for examiners evaluating suppression patterns [18]Verified OSS-3: Objective Scoring System Version 3
Confirms OSS-3 is a validated computerized scoring algorithm developed by Nelson, Handler, and Krapohl with demonstrable validity across multiple samples. The study compared the Backster Either-Or Rule against the federal scoring system and the Matte Quadri-Track system, demonstrating how different approaches handle various response patterns including suppression [18]Verified OSS-3: Objective Scoring System Version 3
Confirms OSS-3 is a validated computerized scoring algorithm developed by Nelson, Handler, and Krapohl with demonstrable validity across multiple samples. For more on how scoring works, see our guide to what a numerical score means in polygraph.

Computerized Scoring Algorithms

Modern computerized scoring algorithms complement manual analysis by providing objective, mathematically derived probability assessments. The OSS-3 (Objective Scoring System, Version 3), developed by Raymond Nelson, Mark Handler, and Donald Krapohl, is a powerful computerized algorithm that calculates a probabilistic classifier for both diagnostic and screening polygraphs [19]Verified LXSoftware — Lafayette Instrument Company
Confirms LXSoftware is bundled with the OSS-3 scoring algorithm and supports Lafayette LX4000, LX5000, LX6, and LX7 systems. The OSS-3 uses a logistic regression formula trained on large datasets of confirmed truth and deception outcomes, with inputs including respiratory suppression patterns [19]Verified LXSoftware — Lafayette Instrument Company
Confirms LXSoftware is bundled with the OSS-3 scoring algorithm and supports Lafayette LX4000, LX5000, LX6, and LX7 systems. The algorithm is bundled with Lafayette's LXSoftware [20]Verified Appendix F: Computerized Scoring of Polygraph Data — The Polygraph and Lie Detection (NRC 2003)
Confirms PolyScore developed by Johns Hopkins APL and CPS developed by Scientific Assessment Technologies (University of Utah), reviewed by the National Research Council.

PolyScore, developed by the Johns Hopkins University Applied Physics Laboratory, uses logistic regression and evaluates signal patterns across all three primary physiological channels [21]Verified Tech Talk: Introduction to the Lafayette OSS-3 Test of Proportions to Discriminate Countermeasures and Random Artifacts
Describes the OSS-3 test of proportions as a statistical method to discriminate countermeasures from random artifacts in polygraph data. The Computerized Polygraph System (CPS), developed by Scientific Assessment Technologies based on research at the University of Utah, uses linear discriminant function analysis to estimate the probability of deception [21]Verified Tech Talk: Introduction to the Lafayette OSS-3 Test of Proportions to Discriminate Countermeasures and Random Artifacts
Describes the OSS-3 test of proportions as a statistical method to discriminate countermeasures from random artifacts in polygraph data. Both PolyScore and CPS have been extensively evaluated by the National Research Council [21]Verified Tech Talk: Introduction to the Lafayette OSS-3 Test of Proportions to Discriminate Countermeasures and Random Artifacts
Describes the OSS-3 test of proportions as a statistical method to discriminate countermeasures from random artifacts in polygraph data.

The OSS-3 also includes a supplemental statistic — the test of proportions — which enables examiners to scientifically evaluate whether data artifacts appear at a statistically significant rate at relevant versus comparison questions [22]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms single-issue diagnostic testing accuracy of 89% (CI 83%-95%) and multiple-issue accuracy of 85% (CI 77%-93%) across validated techniques. This feature is particularly valuable for distinguishing genuine suppression from systematic countermeasure attempts.

These algorithms serve as decision-support tools, enhancing but not replacing the expert examiner's interpretation [19]Verified LXSoftware — Lafayette Instrument Company
Confirms LXSoftware is bundled with the OSS-3 scoring algorithm and supports Lafayette LX4000, LX5000, LX6, and LX7 systems. The hybrid approach of computer-assisted, examiner-driven analysis represents the modern standard of forensic psychophysiology.

How Examiners Differentiate Genuine Suppression

One of the most important skills a polygraph examiner must possess is the ability to distinguish involuntary suppression responses from deliberate countermeasure attempts. When an examinee tries to manipulate their physiological responses — such as by deliberately controlling breathing patterns, performing mental arithmetic at comparison questions, or using physical countermeasures — the resulting chart activity may superficially resemble suppression but exhibits distinct characteristics.

True involuntary apneas almost always occur near the bottom of the exhalation cycle, while deliberate breath-holding often begins at mid-inspiration or full inspiration [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms standardized polygraph terminology including suppression, apnea scoring criteria, and the seven-position numerical scale used in chart analysis. Genuine respiratory suppression typically shows a gradual onset and natural recovery, whereas countermeasure-driven changes tend to be abrupt and mechanical. The dual pneumograph channels (thoracic and abdominal) are particularly revealing: involuntary suppression usually affects both channels proportionally, while deliberate manipulation often produces discordant patterns between chest and abdominal breathing.

The OSS-3 test of proportions provides a statistical tool to identify when activity artifacts occur disproportionately at one type of question, flagging potential countermeasure use [22]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms single-issue diagnostic testing accuracy of 89% (CI 83%-95%) and multiple-issue accuracy of 85% (CI 77%-93%) across validated techniques. If artifacts consistently appear only at comparison questions, the data statistically support a conclusion that the patterns differ between question types, potentially indicating deliberate manipulation. For more on this critical topic, see our guide to polygraph countermeasures detection.

Individual Differences and Testing Variables

Several factors influence whether an examinee's dominant response pattern will be augmentation or suppression. Baseline autonomic tone varies significantly between individuals — some people naturally have higher parasympathetic tone, predisposing them toward suppression patterns. Age, physical fitness, medication use, and psychological condition can all influence whether suppression or augmentation predominates.

The type of polygraph technique used can also affect response patterns. Different test formats structure questions and timing differently, which may influence the balance of suppression and augmentation across channels. The Federal Zone Comparison Technique, for example, uses specific question sequences designed to optimize the detection of both response types.

Environmental factors during the examination — room temperature, seating position, noise levels — can affect baseline physiological states and influence the manifestation of suppression. Trained examiners account for these variables by establishing a clear physiological baseline and monitoring for environmental artifacts that could mimic or mask genuine suppression responses. For insights on managing such challenges, see our guide on handling difficult examinees.

The APA's 2011 meta-analytic survey of validated techniques found that single-issue (event-specific) diagnostic testing produced an aggregated decision accuracy of 89%, with a confidence interval of 83%–95% and an inconclusive rate of 11% Verified Iacono and Ben-Shakhar's Response to Ginton (2020): Validity Estimates from Paired Testing
Foundational research relevant to discussions of polygraph validity estimation methodology. Multiple-issue techniques achieved 85% accuracy (CI 77%–93%) Verified Iacono and Ben-Shakhar's Response to Ginton (2020): Validity Estimates from Paired Testing
Foundational research relevant to discussions of polygraph validity estimation methodology. These figures encompass both augmentation and suppression response patterns, demonstrating that properly trained examiners effectively identify both.

Suppression Is Normal and Expected

If you are preparing for a polygraph examination, it is important to understand that suppression responses are a normal part of human physiology. Every person responds to stress differently, and a trained polygraph examiner expects to see a mix of response patterns including both augmentation and suppression. The presence of suppression at relevant questions does not automatically mean a finding of deception — it is one element within a comprehensive analysis that includes multiple charts, all channels, and validated scoring protocols.

Modern polygraph science — supported by validated techniques, computerized scoring algorithms, and decades of peer-reviewed research — is specifically designed to account for individual differences in physiological response patterns. Whether your body tends toward augmentation or suppression, the examination process captures and evaluates your unique response profile across multiple data collection periods.

The most productive approach for any polygraph examinee is simple honesty. Truthful examinees typically show stronger responses to comparison questions than to relevant questions — regardless of whether those responses manifest as augmentation or suppression. Attempting to control or manipulate your physiological responses is counterproductive and detectable through tools like the OSS-3 test of proportions and trained behavioral observation [22]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms single-issue diagnostic testing accuracy of 89% (CI 83%-95%) and multiple-issue accuracy of 85% (CI 77%-93%) across validated techniques.

For a comprehensive overview of what to expect, explore our polygraph test formats guide and our explanation of the Directed Lie Test.