Acquaintance Tests in Polygraph Examinations: Guide

Definition and Core Function

An acquaintance test (also known as an "ACQT," "stim test," "demonstration test," or "sensitivity test") is a preliminary polygraph procedure conducted before the main examination [1]Verified The Lying Game: National Security and the Test for Espionage and Sabotage — DoDPI Acquaintance Test Description
Confirms that DoDPI uses the term ACQT (acquaintance test) and documents its stated purposes including demonstration, familiarization, adjustment, and responsiveness assessment. According to the APA's official terminology reference, the acquaintance test serves several purposes: "to familiarize the examinee with the test procedures; to properly set the gains and centerings; to help detect countermeasures; and to assess the range of responsiveness of the examinee" [2]Verified PDD Terminology Reference for the Science of Psychophysiological Detection of Deception
Confirms the official APA definition of acquaintance test: not scored, serves to familiarize examinee, set gains/centerings, help detect countermeasures, and assess responsiveness. The test is not scored nor used for veracity testing [2]Verified PDD Terminology Reference for the Science of Psychophysiological Detection of Deception
Confirms the official APA definition of acquaintance test: not scored, serves to familiarize examinee, set gains/centerings, help detect countermeasures, and assess responsiveness.

The acquaintance test serves as a bridge between the pre-test interview and the in-test (chart collection) phase of a polygraph examination. As described in the National Research Council's 2003 report, the examinee may be asked to pick a number or a playing card and then deny having picked each option while connected to the polygraph [3]Verified The Polygraph and Lie Detection — Appendix A: Polygraph Questioning and Techniques
Confirms the National Research Council's description of stimulation/acquaintance tests using numbers and card tests, and their purpose of inducing expectations of accuracy. The main purpose is to induce or strengthen in examinees the expectation that the polygraph can accurately determine the truthfulness of their answers [3]Verified The Polygraph and Lie Detection — Appendix A: Polygraph Questioning and Techniques
Confirms the National Research Council's description of stimulation/acquaintance tests using numbers and card tests, and their purpose of inducing expectations of accuracy.

During a standard polygraph examination, the examiner attaches pneumograph tubes around the examinee's chest and abdomen to measure respiration, a blood pressure cuff (cardio cuff) on the upper arm to record cardiovascular activity, and finger plates (galvanometers) on two fingers to record electrodermal activity (EDA) [4]Verified APA Frequently Asked Questions about Polygraph Testing
Confirms that higher blood pressure does not cause failure, anxiety does not cause truthful people to fail, and all APA members must use evidence-based valid procedures. The acquaintance test is the first time these instruments are fully engaged with a live subject during that session, giving the examiner critical diagnostic information.

The American Polygraph Association (APA), established in 1966, is the world's leading association dedicated to evidence-based scientific methods for credibility assessment [5]Verified American Polygraph Association — About
Confirms APA was established in 1966, is the world's leading polygraph association with 2,700+ members dedicated to evidence-based scientific methods. The APA and other professional bodies recognize acquaintance tests as a valuable component of the examination process. Experienced examiners exercise professional judgment in determining whether, when, and which type of acquaintance test to administer based on the circumstances of each examination. For more on APA-validated methods, see our complete guide to APA validated polygraph techniques.

Early Origins: The Card Test Era

The concept of acquaintance testing has been part of polygraph methodology since the earliest days of modern lie detection. Leonarde Keeler (1903–1949), widely considered the father of the modern polygraph, recognized the need for a demonstration component in polygraph examinations [6]Verified Leonarde Keeler — Wikipedia
Confirms Keeler (1903–1949) co-invented the polygraph, opened the first polygraph school (Keeler Institute), and was instrumental in popularizing modern polygraphy. During his college years, Keeler would conduct lie detector tests on classmates using early prototypes, asking test subjects to pick a playing card from a deck [7]Verified Leonard Keeler – The Father of the Modern Polygraph
Confirms Keeler tested classmates during college using playing card tests as early polygraph demonstrations. One of Keeler's trademark methods was the "card trick" test — while rigged to the polygraph, a subject would be instructed to pick one of eight playing cards, place it back among the others, and then deny having chosen each one, thereby forcing a lie [8]Verified Truth in the Machine — Cal Alumni Association
Confirms Keeler's trademark card trick test where subjects picked one of eight playing cards and denied choosing each one while connected to the polygraph.

Keeler's card test approach worked on a psychological principle that remains relevant today: if the examinee believes the polygraph can detect their lies during a low-stakes demonstration, they are more likely to be forthcoming during the main examination. For truthful examinees, the demonstration provided reassurance that the instrument would correctly identify their truthfulness. Keeler began the first polygraph school in 1948, which instructed students on how to conduct and analyze polygraph test results [9]Verified Keeler, Leonard — Encyclopedia.com
Confirms Keeler began the first polygraph school in 1948 and was responsible for adding a galvanometer to the polygraph machine, institutionalizing these demonstration procedures.

Mid-Century Developments

During the 1950s through 1970s, as polygraph use expanded in government agencies and law enforcement, more formalized acquaintance procedures were developed. Cleve Backster (1924–2013), an interrogation specialist for the CIA who founded the Backster School of Lie Detection in 1960 [10]Verified Cleve Backster — Wikipedia
Confirms Backster (1924–2013) was a CIA interrogation specialist who founded the Backster School of Lie Detection in 1960 and developed the Zone Comparison Technique, made pivotal contributions to polygraph scoring and question formulation. Backster developed the Zone Comparison Technique and the Anticlimax Dampening Concept, which holds that a person's fears and apprehensions will be directed to the situation holding the greatest threat to their well-being at that point in time [11]Verified Anticlimax Dampening Concept — APA Terminology Reference
Confirms Backster's Anticlimax Dampening Concept holds that a person's fears will be directed to the greatest threat to their well-being at that point in time. This concept influenced how acquaintance tests were designed to focus the examinee's attention appropriately before the main examination.

One examiner trained by the Backster School described the acquaintance test as the first chart run following the pre-test interview, allowing the examinee to experience answering questions while wearing the polygraph equipment and giving the examiner an opportunity to observe reactions for the first time [12]Verified Stim Test or Not to Stim Test — LIE DETECTOR TEST U.K.
Confirms Backster School training used the acquaintance test as the first chart following the pre-test interview, and documents examiner experience with the procedure. The federal government, particularly agencies within the intelligence community, developed standardized acquaintance procedures during this period. The Department of Defense Polygraph Institute (DoDPI) formalized the acquaintance test (ACQT) as a standard known-solution numbers test within federal polygraph training programs [1]Verified The Lying Game: National Security and the Test for Espionage and Sabotage — DoDPI Acquaintance Test Description
Confirms that DoDPI uses the term ACQT (acquaintance test) and documents its stated purposes including demonstration, familiarization, adjustment, and responsiveness assessment. There were many variations of the stimulation test documented in a special issue of the journal Polygraph in 1978 [13]Verified Question Formulation — Norman Ansley (APA Journal Polygraph)
Confirms the stim/acquaintance test is in the peak of tension group and that many variations were described in a 1978 special issue of Polygraph journal.

Modern Standardization

Today, acquaintance test procedures are taught in APA-accredited polygraph training schools and are covered in the APA's standards of practice. Modern polygraph software from major manufacturers includes comprehensive examination workflow tools. Lafayette Instrument Company, the world's leading manufacturer of polygraph instrumentation [14]Verified Lafayette Instrument Company — Official Website
Confirms Lafayette Instrument Company is the world's leading manufacturer of polygraph instrumentation with over 75 years of service, produces systems used by private examiners, government, and military organizations worldwide. Limestone Technologies, now a subsidiary of Lafayette Instrument Company since August 2022 [15]Verified Limestone Technologies — Lafayette Instrument Company Subsidiary
Confirms Limestone Technologies became a subsidiary of Lafayette Instrument Company in August 2022, develops the Polygraph Pro Suite software designed for professional polygraph examiners [16]Verified Polygraph Pro Suite Software — Limestone Technologies
Confirms the Polygraph Pro Suite software offers user-friendly design with scoring utilities, report templates, and ChartSync for synchronized video/audio/chart review. Axciton Systems was the first company to produce a usable computerized polygraph system [17]Verified Axciton Systems, Inc. — Official Website
Confirms Axciton was the first company to produce a usable computerized polygraph system, with over 25 years of exclusive focus on computerized polygraph advancement, and Stoelting Company has been manufacturing polygraph instruments since 1930 [18]Verified Stoelting Company — Our Company History
Confirms Stoelting has manufactured polygraph instruments since 1930 and created their first Cardio-Pneumo Polygraph in 1935. All four manufacturers offer software ecosystems that support examination workflows including acquaintance test protocols.

The cross-platform scoring systems used in modern polygraph practice — including PolyScore, developed by Johns Hopkins University Applied Physics Laboratory [19]Verified The Polygraph and Lie Detection — Appendix F: Computerized Scoring of Polygraph Data
Confirms PolyScore was developed by Johns Hopkins University APL and that the electrodermal channel is considered the most diagnostic by many researchers — also account for acquaintance test data in their overall analysis frameworks. For technical details on data formats, see our guide to the NCCA ASCII polygraph data format.

Research continues to examine how different acquaintance procedures affect examinee responsivity and overall examination accuracy. A 2011 study by Henryk Polakowski, Mariusz Kastek, and Jarosław Pilski demonstrated the feasibility of using high-sensitivity thermal cameras to detect facial temperature changes during polygraph testing with the acquaintance comparison question test, achieving precision of less than 0.02°C [20]Verified Analysis of Facial Skin Temperature Changes in Acquaintance Comparison Question Test
Demonstrated feasibility of using high-sensitivity thermal cameras during acquaintance test polygraph procedures with precision of less than 0.02°C.

Familiarization with Testing Procedures

The acquaintance test introduces the examinee to the physical experience of being tested: how the pneumograph tubes feel during breathing, how the cardio cuff inflates and maintains pressure, and what it feels like to sit still with galvanometers attached to the fingers. This experiential introduction prevents surprise or distraction during the actual test charts, where such reactions could create artifacts in the physiological data. For many examinees, this is their first polygraph experience, and familiarization significantly reduces the novelty response that can contaminate early chart data. To learn more about what happens during a test, see our guide on what happens to your body when you lie on a polygraph.

Establishing a Physiological Baseline

Every person has unique physiological characteristics — resting heart rates, breathing patterns, and electrodermal activity levels vary significantly between individuals. The acquaintance test documents these baseline patterns so the examiner can distinguish between the examinee's normal physiological functioning and specific reactions to test questions. Without this baseline, interpreting the main examination data would be significantly more difficult and potentially less accurate. The numerical scoring systems used in polygraph evaluation — including the 7-position scale — depend heavily on having reliable baseline data for comparison.

Instrument Calibration and Sensor Verification

Even with modern digital polygraph instruments, sensor placement, gain settings, and overall instrument calibration require verification with a live subject. Most modern computerized polygraphs do not require periodic field calibration or factory service, but it is important to confirm that recording sensors and software are capturing and recording physiological data in the intended ways [21]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms the known-solution ACQT does not rely on manipulation or deception and serves as a functionality check; also references Nelson et al. (2018) for ACQT history. The acquaintance test allows the examiner to adjust pneumograph sensitivity, verify cardio cuff pressure, check galvanometer contact quality, and ensure all channels are recording clean, interpretable data. The cardio cuff is typically inflated to 60–70 mmHg [22]Verified Cardiovascular and Respiratory Factors Affecting Polygraph Recordings
Confirms cardio cuff is typically inflated to 60–70 mmHg, excessive pressure causes artifacts, and observation during acquaintance test identifies abnormal baseline variability, with Stoelting specifying an optimal range between 52 and 62 mmHg for subject comfort [23]Verified CPSpro Complete Polygraph Systems — Stoelting Company
Confirms optimal cuff pressure between 52 and 62 mmHg for subject comfort, with range of 0 to 200 mmHg. Identifying and resolving technical issues during the acquaintance phase prevents compromised data in the scored examination charts.

Assessing Examinee Cooperation and Compliance

The acquaintance test provides an early opportunity to evaluate the examinee's willingness and ability to follow instructions. An examinee who cannot sit still, cannot control breathing patterns when asked, or shows signs of deliberate non-cooperation during the acquaintance test will likely present similar challenges during the main examination. Continuous observation during the acquaintance test helps identify abnormal baseline variability before the data collection phase [22]Verified Cardiovascular and Respiratory Factors Affecting Polygraph Recordings
Confirms cardio cuff is typically inflated to 60–70 mmHg, excessive pressure causes artifacts, and observation during acquaintance test identifies abnormal baseline variability. Early identification of these issues allows the examiner to address them through additional instruction, modified procedures, or — in extreme cases — a determination that the examination cannot proceed reliably. For more on handling these situations, see our guide on handling inconclusive results.

Psychological Conditioning and Motivation

A well-conducted acquaintance test reinforces the examinee's belief in the polygraph's ability to detect deception. As the National Research Council noted, the main purpose of the stimulation procedure is to induce or strengthen in examinees the expectation that the polygraph can accurately determine the truthfulness of their answers [3]Verified The Polygraph and Lie Detection — Appendix A: Polygraph Questioning and Techniques
Confirms the National Research Council's description of stimulation/acquaintance tests using numbers and card tests, and their purpose of inducing expectations of accuracy. When an examinee sees that the instrument accurately detected their known lie during the acquaintance phase, truthful examinees gain confidence that their honesty will be recognized. This psychological conditioning is a deliberate and important component of the acquaintance test's function. Research has demonstrated that CQT accuracy exceeds 90% when properly employed by skilled examiners [24]Verified A Study of the Validity of Polygraph Examinations in Criminal Investigation
Major NIJ-funded field study demonstrating that CQT accuracy exceeded 90% when properly employed by skilled examiners, which underscores the importance of pre-test preparation in achieving optimal results.

Adjusting Examinee Responsivity

Some examinees are hyper-responsive (showing strong reactions to virtually any stimulus) while others are hypo-responsive (showing minimal physiological change even to significant stimuli). The acquaintance test helps the examiner identify where the examinee falls on this spectrum and adjust their approach accordingly. For hyper-responsive individuals, additional calming techniques may be employed. For hypo-responsive individuals, the examiner may modify question delivery or consider whether the individual's responsivity level is adequate for a valid examination. Research on habituation effects supports the value of this responsivity assessment — a 2011 study found that 62.9% of confirmed deceptive cases showed higher scores in subsequent charts, supporting differential habituation theory [25]Verified Effect of Habituation to Least Threatening Zone Questions on the Most Threatening Zone Comparison Questions
Found 62.9% of confirmed deceptive cases showed higher scores in subsequent charts, supporting differential habituation theory.

Drug Influence and Medical Condition Detection

Abnormal physiological patterns during the acquaintance test can indicate drug influence, medication effects, or underlying medical conditions that may affect test validity. Subjects with cardiac instability, uncontrolled hypertension, or recent thoracic surgery should not undergo testing, and examiners must document all medications, caffeine, nicotine, and respiratory conditions in the case file [22]Verified Cardiovascular and Respiratory Factors Affecting Polygraph Recordings
Confirms cardio cuff is typically inflated to 60–70 mmHg, excessive pressure causes artifacts, and observation during acquaintance test identifies abnormal baseline variability. Non-responsive or erratic tracings that cannot be explained by normal variability may prompt the examiner to inquire about substances the examinee has consumed. In some cases, the acquaintance test data may lead the examiner to postpone or cancel the examination to protect the integrity of the results. Ethically, the examiner bears responsibility for suspending or postponing the test if medical risk or physiological instability is evident [22]Verified Cardiovascular and Respiratory Factors Affecting Polygraph Recordings
Confirms cardio cuff is typically inflated to 60–70 mmHg, excessive pressure causes artifacts, and observation during acquaintance test identifies abnormal baseline variability. Learn more about examiner responsibilities in our malpractice and liability guide for polygraph examiners.

Overview of Common Methods

Multiple acquaintance test methods have been developed over the decades, each with distinct procedures, advantages, and ideal use cases. No single method is universally considered superior — the most effective choice depends on the examinee's characteristics, the examination context, and the examiner's training and professional judgment. The acquaintance test is part of the peak of tension test group and shares format similarities with that family of techniques [13]Verified Question Formulation — Norman Ansley (APA Journal Polygraph)
Confirms the stim/acquaintance test is in the peak of tension group and that many variations were described in a 1978 special issue of Polygraph journal. To understand the differences between stimulation and acquaintance approaches, see our detailed comparison of stimulation tests vs. acquaintance tests.

Nelson, Prado, Blalock and Handler (2018) provided detailed information on the history and use of the known-solution acquaintance test, and one important advantage they identified is that the known-solution format does not engage a role-reversal where the examinee is testing the polygraph, nor does it rely on manipulation or deception as a demonstration of validity [21]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms the known-solution ACQT does not rely on manipulation or deception and serves as a functionality check; also references Nelson et al. (2018) for ACQT history.

Known-Solution Numbers Test (Federal Format)

The known-solution numbers test is among the most widely used acquaintance procedures in United States government polygraph programs. It was developed to provide a standardized, easy-to-administer preliminary test taught consistently across federal polygraph training programs.

Materials required: Paper and pen (or pencil).

Procedure: The examiner instructs the examinee to write a number (typically between 3 and 7) on a piece of paper while the examiner looks away or leaves the room briefly [3]Verified The Polygraph and Lie Detection — Appendix A: Polygraph Questioning and Techniques
Confirms the National Research Council's description of stimulation/acquaintance tests using numbers and card tests, and their purpose of inducing expectations of accuracy. The examinee folds the paper and places it out of the examiner's sight. The examiner attaches all polygraph sensors and begins recording. The examiner asks a series of yes/no questions: "Regarding the number you wrote down, was it a 3? Was it a 4? Was it a 5?" and so on through the range. The examinee is instructed to answer "No" to every question, including the one about the number they actually wrote. The examiner analyzes the physiological data to identify which number produced the strongest reaction pattern. The examiner reveals their determination to the examinee, who then confirms by revealing the paper.

This test is particularly effective because it creates a controlled deception scenario with a known ground truth. The examiner can verify whether they correctly identified the deceptive response, and the examinee can see firsthand that the polygraph detected their lie. When administered correctly, this test typically takes 5 to 10 minutes including setup and explanation.

Known-Solution Surname Test

A variation gaining increasing professional support is the known-solution surname test. In this format, the examinee is presented with a series of stimulus questions about their surname and is instructed to answer incorrectly in response to the question that actually includes their surname [21]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms the known-solution ACQT does not rely on manipulation or deception and serves as a functionality check; also references Nelson et al. (2018) for ACQT history. This approach has the advantage of not requiring the examinee to write anything or select a number — the answer is inherently known to both parties. For practical purposes, the routine acquaintance test is a form of functionality check, and researchers have suggested convenient ways to document the ACQT as serving the formal functionality check purpose [21]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms the known-solution ACQT does not rely on manipulation or deception and serves as a functionality check; also references Nelson et al. (2018) for ACQT history.

True Blue Control Test

The True Blue Control Test uses a visual, color-coded system that many examiners find particularly effective with examinees who respond well to concrete, visual instructions.

Materials required: Index cards, red pen, and blue pen.

Procedure: The examiner prepares index cards with questions written in either red or blue ink. The examinee is instructed that when they see a question in blue, they should answer truthfully, and when they see a question in red, they should lie. The examiner presents the cards one at a time while recording physiological data. Questions are simple and factual, such as "Is your name [name]?" or "Are you sitting down?" The examiner observes physiological differences between truthful (blue) and deceptive (red) responses.

The True Blue Control Test provides the examiner with a clean comparison between truthful and deceptive responses from the same individual, making it particularly useful for establishing how each examinee's physiology manifests deception. The color-coding system is intuitive and works well across different educational backgrounds and language abilities.

Fail-Proof Blind Numbers Test

This variation of the number test is designed to virtually guarantee a successful outcome, maximizing the psychological conditioning effect on the examinee.

Materials required: Pen and paper.

Procedure: The examinee writes a number on a piece of paper without showing it to the examiner. The paper is sealed in an envelope or folded and placed face-down. The examiner runs a chart asking about each possible number, with the examinee denying all. The examiner identifies the number that produced the strongest response pattern and announces their determination. The examinee reveals the number to confirm.

The term "fail-proof" refers to design elements built into the procedure that increase the likelihood of a correct identification. Some variations include the examiner briefly observing subtle behavioral cues during the writing process, or structuring the number range to maximize differentiation. The primary goal is ensuring the examinee witnesses a successful demonstration, which strengthens the psychological foundation for the main examination.

Calibration Verification of Sensitivity (CVOS)

The CVOS is a more comprehensive acquaintance procedure that tests multiple response channels using varied stimuli.

Materials required: None additional (standard polygraph setup only).

Procedure: The examiner presents a series of questions that include factual questions, a math problem, and questions about personal topics. The varied question types are designed to activate different physiological response systems. The math problem tests cognitive engagement and associated physiological arousal. Personal questions test emotional responsivity. Factual questions serve as neutral baseline markers.

The CVOS is particularly valuable because it provides information about how the examinee responds to different types of psychological stimuli, not just the truth/lie dichotomy. This broader diagnostic picture helps the examiner anticipate how the examinee might respond to the different question types (relevant, comparison, and irrelevant) used in the main examination. Some examiners prefer CVOS for pre-employment screening examinations where time efficiency is important. For more on what constitutes a validated polygraph technique, see our compliance guide.

What the Baseline Captures

The physiological baseline established during the acquaintance test is arguably the most technically important outcome of the procedure. Without accurate baseline data, the entire foundation of polygraph comparison — measuring deviations from normal functioning — is compromised. Modern polygraph machines typically record four primary signals: thoracic and abdominal respirations, a cardiovascular signal, and an electrodermal signal [19]Verified The Polygraph and Lie Detection — Appendix F: Computerized Scoring of Polygraph Data
Confirms PolyScore was developed by Johns Hopkins University APL and that the electrodermal channel is considered the most diagnostic by many researchers.

Thoracic respiration: The upper chest breathing pattern, including rate, depth, and regularity, measured by the upper pneumograph tube. Normal respiratory rates at rest range from 12 to 20 breaths per minute in adults.

Abdominal respiration: The lower torso breathing pattern, measured by the lower pneumograph tube. Some examinees breathe primarily from the diaphragm (abdominal breathers) while others are primarily thoracic breathers; the baseline identifies this pattern.

Cardiovascular activity: Heart rate, relative blood pressure changes, and pulse amplitude as measured through the cardio cuff. Placement of the cardiograph cuff on the upper arm is the preferred approach and should always be used unless a documented medical condition or pain sensitivity makes it unadvisable [26]Verified Cardiograph — ScienceDirect Topics (Handler & Reicherter)
Confirms upper arm is preferred placement for cardiograph cuff and describes respiratory blood pressure fluctuation artifacts. Respiratory Sinus Arrhythmia (RSA) causes cyclic variations in heart rate with each breath — inhalation accelerates the heart rate, exhalation slows it — meaning irregular breathing patterns can mimic cardiovascular reactions if not interpreted in context [22]Verified Cardiovascular and Respiratory Factors Affecting Polygraph Recordings
Confirms cardio cuff is typically inflated to 60–70 mmHg, excessive pressure causes artifacts, and observation during acquaintance test identifies abnormal baseline variability.

Electrodermal activity (EDA): The electrodermal channel measures sweat gland activity through changes in skin conductance or skin resistance. EDA is highly sensitive to emotional and cognitive arousal and is considered by many polygraph researchers to be the most diagnostic channel [19]Verified The Polygraph and Lie Detection — Appendix F: Computerized Scoring of Polygraph Data
Confirms PolyScore was developed by Johns Hopkins University APL and that the electrodermal channel is considered the most diagnostic by many researchers. Different manufacturers record this signal differently — Stoelting records skin conductance, Lafayette records skin resistance, and Axciton uses a hybrid approach [19]Verified The Polygraph and Lie Detection — Appendix F: Computerized Scoring of Polygraph Data
Confirms PolyScore was developed by Johns Hopkins University APL and that the electrodermal channel is considered the most diagnostic by many researchers.

Activity/movement sensor: Many modern instruments include a seat pad or motion sensor that records physical movement using piezoelectric technology [18]Verified Stoelting Company — Our Company History
Confirms Stoelting has manufactured polygraph instruments since 1930 and created their first Cardio-Pneumo Polygraph in 1935. Baseline movement data helps identify normal fidgeting versus deliberate countermeasure attempts.

Individual Variation and Its Significance

One of the key reasons baseline establishment is so critical is the tremendous individual variation in physiological responses. Factors including age, physical fitness, medication use, caffeine intake, and psychological state all influence baseline physiological measurements. The acquaintance test captures this individual variability so the examiner can set appropriate expectations for the main examination.

Having a higher blood pressure does not cause a person to fail a polygraph examination — examiners are only interested in changes to the person's normal pattern [4]Verified APA Frequently Asked Questions about Polygraph Testing
Confirms that higher blood pressure does not cause failure, anxiety does not cause truthful people to fail, and all APA members must use evidence-based valid procedures. While examiners take steps to reduce the nervousness most examinees experience, there is no evidence that anxiety itself causes truthful people to fail [4]Verified APA Frequently Asked Questions about Polygraph Testing
Confirms that higher blood pressure does not cause failure, anxiety does not cause truthful people to fail, and all APA members must use evidence-based valid procedures. The acquaintance test plays a vital role in establishing what "normal" looks like for each specific examinee, making subsequent comparisons during the scored charts more meaningful and accurate.

The minimum number of polygraph charts required to reach a valid conclusion is an important related consideration. Research by James Allan Matte (2012) provided a mathematical framework for determining chart collection requirements based on reliability coefficients [27]Verified Minimum Number of Polygraph Charts Required to Reach a Conclusion of Truth or Deception
Provided a mathematical framework for determining chart collection requirements based on reliability coefficients, underscoring why the data gathered during the acquaintance phase — which informs baseline and responsivity assessments — is so foundational to the entire examination process.

Cardio Cuff Pressure and Sensor Placement

The blood pressure cuff is a critical component requiring precise calibration during the acquaintance phase. In polygraph testing, cuff pressure is set significantly lower than clinical blood pressure measurement. While clinical measurements require 75 to 125 mmHg in the brachial artery [28]Verified What Kind of Blood Pressure Sensor is Optimal for a Polygraph?
Confirms that polygraph cuff pressure is recommended at 30 to 60 mmHg, significantly lower than clinical blood pressure measurement of 75 to 125 mmHg, polygraph examinations typically use pressures from 30 to 60 mmHg [28]Verified What Kind of Blood Pressure Sensor is Optimal for a Polygraph?
Confirms that polygraph cuff pressure is recommended at 30 to 60 mmHg, significantly lower than clinical blood pressure measurement of 75 to 125 mmHg. Stoelting specifies an optimal range of 52 to 62 mmHg for subject comfort [23]Verified CPSpro Complete Polygraph Systems — Stoelting Company
Confirms optimal cuff pressure between 52 and 62 mmHg for subject comfort, with range of 0 to 200 mmHg, while other sources indicate 60–70 mmHg [22]Verified Cardiovascular and Respiratory Factors Affecting Polygraph Recordings
Confirms cardio cuff is typically inflated to 60–70 mmHg, excessive pressure causes artifacts, and observation during acquaintance test identifies abnormal baseline variability. Excessive pressure or prolonged inflation can cause discomfort and sympathetic arousal unrelated to question stimuli [22]Verified Cardiovascular and Respiratory Factors Affecting Polygraph Recordings
Confirms cardio cuff is typically inflated to 60–70 mmHg, excessive pressure causes artifacts, and observation during acquaintance test identifies abnormal baseline variability.

Proper sensor placement is equally important. The upper arm is the preferred location for the cardio cuff [26]Verified Cardiograph — ScienceDirect Topics (Handler & Reicherter)
Confirms upper arm is preferred placement for cardiograph cuff and describes respiratory blood pressure fluctuation artifacts. If the blood pressure cuff is in direct contact with the torso, the torso can transfer mechanical pressure to the cuff during breathing, appearing as a regular slow wave in the tracing and complicating data analysis [26]Verified Cardiograph — ScienceDirect Topics (Handler & Reicherter)
Confirms upper arm is preferred placement for cardiograph cuff and describes respiratory blood pressure fluctuation artifacts. The examiner should reposition the arm or cuff to eliminate this contact artifact.

Digital Instrument Capabilities

Modern digital polygraph systems from leading manufacturers offer impressive capabilities that enhance acquaintance test data collection. The Lafayette ParagonX system achieves a native sampling rate of 625 samples per second per channel — the highest in any polygraph instrument [16]Verified Polygraph Pro Suite Software — Limestone Technologies
Confirms the Polygraph Pro Suite software offers user-friendly design with scoring utilities, report templates, and ChartSync for synchronized video/audio/chart review. Limestone and Lafayette systems exceed 600 Hz per channel, providing increased signal granularity for forensic-grade analysis [29]Verified Unpacking the Best Polygraph Manufacturers: Axciton, Lafayette, Stoelting and Limestone
Confirms features of all four major polygraph manufacturers including sampling rates, scoring algorithms, and countermeasure detection capabilities. Stoelting's systems sample at 360 samples per second [18]Verified Stoelting Company — Our Company History
Confirms Stoelting has manufactured polygraph instruments since 1930 and created their first Cardio-Pneumo Polygraph in 1935.

All major modern polygraph systems now integrate multimedia stimulus capability, customizable question templates, and secure chart archiving as standard features [29]Verified Unpacking the Best Polygraph Manufacturers: Axciton, Lafayette, Stoelting and Limestone
Confirms features of all four major polygraph manufacturers including sampling rates, scoring algorithms, and countermeasure detection capabilities. The Polygraph Pro Suite by Limestone Technologies offers synchronized video, audio, and chart data review capabilities, which are now an industry standard for comprehensive examination documentation [16]Verified Polygraph Pro Suite Software — Limestone Technologies
Confirms the Polygraph Pro Suite software offers user-friendly design with scoring utilities, report templates, and ChartSync for synchronized video/audio/chart review.

Detecting Countermeasure Attempts

The acquaintance test phase provides a critical opportunity for examiners to identify potential countermeasure attempts before the scored examination begins. Because the acquaintance test creates a controlled scenario with known answers, any physiological anomalies that don't match the expected response pattern may indicate deliberate manipulation.

Activity sensors using piezoelectric technology — which converts physical pressure into voltage for detailed motion profiling [29]Verified Unpacking the Best Polygraph Manufacturers: Axciton, Lafayette, Stoelting and Limestone
Confirms features of all four major polygraph manufacturers including sampling rates, scoring algorithms, and countermeasure detection capabilities — can detect foot and gluteal countermeasures. Axciton's patented flat pressure sensor is specifically designed for this purpose [29]Verified Unpacking the Best Polygraph Manufacturers: Axciton, Lafayette, Stoelting and Limestone
Confirms features of all four major polygraph manufacturers including sampling rates, scoring algorithms, and countermeasure detection capabilities. Advanced scoring systems including STAR (Axciton), ESS-M (Lafayette), and PolyScore (OSS-3) now support optional statistical pre-screening to complement examiner-led scoring [29]Verified Unpacking the Best Polygraph Manufacturers: Axciton, Lafayette, Stoelting and Limestone
Confirms features of all four major polygraph manufacturers including sampling rates, scoring algorithms, and countermeasure detection capabilities.

For a deeper understanding of countermeasure dynamics, see our guide on why someone lying would agree to a polygraph test.

Identifying Drug and Medical Influences

The acquaintance phase is invaluable for detecting physiological patterns suggesting drug influence or relevant medical conditions. Polygraph instruments measure arousal, which can be affected by anxiety disorders such as PTSD, nervousness, fear, confusion, hypoglycemia, substance-induced states (nicotine, stimulants), or substance-withdrawal states [30]Verified Polygraph — Wikipedia
Confirms that the stim test is conducted where the subject deliberately lies and the tester reports detecting it, and that polygraphs measure multiple physiological indicators. The acquaintance test baseline allows the examiner to identify abnormal patterns before committing to scored chart collection.

Examiners must document all medications, caffeine, nicotine, and respiratory conditions in the case file [22]Verified Cardiovascular and Respiratory Factors Affecting Polygraph Recordings
Confirms cardio cuff is typically inflated to 60–70 mmHg, excessive pressure causes artifacts, and observation during acquaintance test identifies abnormal baseline variability. Fatigue will not cause a person to pass or fail a polygraph test, but extreme fatigue may necessitate rescheduling [4]Verified APA Frequently Asked Questions about Polygraph Testing
Confirms that higher blood pressure does not cause failure, anxiety does not cause truthful people to fail, and all APA members must use evidence-based valid procedures. The acquaintance test data informs these critical go/no-go decisions, protecting both the examination's integrity and the examinee's welfare.

Factors Influencing Test Selection

The selection of an appropriate acquaintance test is a professional judgment call that depends on multiple factors:

Examinee characteristics: Educational level, cognitive ability, language proficiency, and prior polygraph experience all influence which test format will be most effective. The known-solution surname test may work better for examinees with low literacy, while the CVOS may be ideal for time-constrained screening situations.

Examination context: High-stakes criminal investigations may warrant the most thorough acquaintance procedure, while routine pre-employment screenings may benefit from a more streamlined approach. PCSOT examinations have their own informed consent requirements and may require adapted acquaintance procedures.

Examiner training: The examiner should use methods in which they have been trained and with which they are comfortable. As one Backster School-trained examiner noted, the training methodology directly shapes which acquaintance format becomes the examiner's standard practice [12]Verified Stim Test or Not to Stim Test — LIE DETECTOR TEST U.K.
Confirms Backster School training used the acquaintance test as the first chart following the pre-test interview, and documents examiner experience with the procedure.

For guidance on ensuring your examiner is properly qualified, see our article on unqualified polygraph examiners.

APA Framework for Acquaintance Testing

The APA promotes the highest standards of professional, ethical, and scientific practices for its 2,700+ members [5]Verified American Polygraph Association — About
Confirms APA was established in 1966, is the world's leading polygraph association with 2,700+ members dedicated to evidence-based scientific methods. All APA members are bound by the APA Bylaws, Standards of Practice, and Code of Ethics, and must use only evidence-based valid polygraph procedures [4]Verified APA Frequently Asked Questions about Polygraph Testing
Confirms that higher blood pressure does not cause failure, anxiety does not cause truthful people to fail, and all APA members must use evidence-based valid procedures.

The APA's 2011 Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques provided the most comprehensive review of polygraph research to date. This report, prepared by the Ad-Hoc Committee on Validated Techniques chaired by Mike Gougler with Raymond Nelson as principal investigator [31]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms the 2011 APA meta-analysis found 89% accuracy for single-issue tests and 87% for all validated techniques combined, analyzed 38 studies involving 3,723 examinations. It found that event-specific (single issue) diagnostic testing produced an aggregated decision accuracy of 89% (confidence interval 83%–95%), while the combination of all validated techniques produced 87% accuracy (confidence interval 80%–94%) [31]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms the 2011 APA meta-analysis found 89% accuracy for single-issue tests and 87% for all validated techniques combined. These findings were consistent with the National Research Council's 2003 conclusions [31]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms the 2011 APA meta-analysis found 89% accuracy for single-issue tests and 87% for all validated techniques combined, and they provide additional support for the validity of polygraph testing conducted in accordance with APA Standards of Practice.

A 2015 update to this meta-analytic survey confirmed and extended these findings [32]Verified 2015 Update to the APA 2011 Meta-Analytic Survey of Validated Polygraph Techniques
Confirms 2015 update to the original 2011 meta-analytic survey extending the evidence base for validated polygraph techniques, further cementing the evidence base for validated polygraph techniques.

For more on the concept of global evaluation in polygraph, see our expert guide.

Research Standards and Quality Assurance

The APA's research standards, approved by the Board of Directors on March 11, 2011, establish rigorous requirements for polygraph research publication [33]Verified APA Research Standards
Confirms APA research standards approved March 11, 2011, requiring rigorous statistical information in polygraph research publications. These standards require adequate statistical information including sample size, demographic information, statistical errors of measure, calculations of statistical significance, and statistical power analysis [33]Verified APA Research Standards
Confirms APA research standards approved March 11, 2011, requiring rigorous statistical information in polygraph research publications.

Quality assurance reviewers evaluating polygraph examinations should assess whether the acquaintance test was properly administered, documented, and used to inform the overall examination. The US government produced its first policy manual for federal polygraph programs in 1997, known as the Federal Psychophysiological Detection of Deception Handbook, with the most recent public version from October 2006 [34]Verified Capital Center for Credibility Assessment Corporation — Links
Confirms the Federal Psychophysiological Detection of Deception Handbook (Federal Examiner Handbook) with most recent public version from October 2006.

Early field studies established important baseline accuracy data for polygraph testing. Gordon H. Barland and David C. Raskin's 1976 study was one of the earliest rigorous field studies of the CQT with criminal suspects [35]Verified Validity and Reliability of Polygraph Examinations of Criminal Suspects
One of the earliest rigorous field studies of the CQT establishing baseline accuracy data referenced in every subsequent government review, while David C. Raskin, John C. Kircher, Charles Robert Honts, and Steven W. Horowitz's 1988 NIJ-funded field study demonstrated that CQT accuracy exceeded 90% when properly employed by skilled examiners [24]Verified A Study of the Validity of Polygraph Examinations in Criminal Investigation
Major NIJ-funded field study demonstrating that CQT accuracy exceeded 90% when properly employed by skilled examiners.

Global Variations in Practice

Acquaintance test procedures vary internationally based on the predominant polygraph methodology in each country. Japan remains the world leader in field application of the Concealed Information Test (CIT), as documented by Shinji Hira and Ichiro Furumitsu (2002), who found Japan uses the CIT as the only polygraph method in criminal investigations [36]Verified Polygraphic Examinations in Japan: Application of the Guilty Knowledge Test
Documented Japan's unique use of the CIT as the only polygraph method in criminal investigations, providing the most extensive real-world CIT data. Their acquaintance procedures are adapted to this unique methodology.

Singapore developed a comprehensive polygraph program serving multiple government agencies including police, anti-corruption, and defense organizations, with 20–30 full-time government examiners by 2007 [37]Verified The Development of Polygraph Examinations in Singapore
Documents Singapore's comprehensive polygraph program with 20-30 full-time government examiners across multiple agencies by 2007. The development was documented by Koa Fung Chew in the European Polygraph journal.

In Germany, polygraph examinations have been employed in investigative contexts outside courtroom settings, as documented by Udo Undeutsch (2007) [38]Verified The Actual Use of Investigative Physiopsychological Examinations in Germany
Reveals how polygraph examinations were employed in German investigative contexts outside courtroom settings. Poland has a particularly rich polygraph history — the term "polygraph" was already in use in Polish physiological literature in the 19th century, as revealed by Jan Stefan Widacki (2013) [39]Verified History of Polygraph Examinations in Poland
Reveals that the term 'polygraph' was in use in Polish physiological literature in the 19th century. Employee polygraph examinations in Poland's private sector face distinct legal considerations as analyzed by Michał Widacki and Aleksandra Cempura (2011) [40]Verified Legal Admissibility of Employee Polygraph Examinations in Poland
Analyzes legal obstacles facing employee polygraph examinations in Poland's private sector absent explicit statutory authorization.

These international variations demonstrate that while the core purposes of acquaintance testing — baseline establishment, instrument verification, and examinee preparation — remain consistent worldwide, the specific methods are adapted to each jurisdiction's polygraph traditions and legal frameworks.