What Is the Acquaintance Test in Polygraph? Full Guide

Definition and Core Purpose

The acquaintance test — also widely known as the stimulation test, stim test, demonstration test, numbers test, or known-truth test — is a short preliminary procedure that polygraph examiners conduct before the main diagnostic examination begins [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms acquaintance test purposes, alternate names (Numbers Test, Demonstration Test, Stim Test, CVOS, etc.), and that it is not scored nor used for veracity testing. According to the official APA Terminology Reference for the Science of Psychophysiological Detection of Deception (4th edition, 2022), authored by Krapohl, Handler, and Lynch, 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 [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms acquaintance test purposes, alternate names (Numbers Test, Demonstration Test, Stim Test, CVOS, etc.), and that it is not scored nor used for veracity testing. Other recognized terms for this procedure include Blind Numbers Test, Calibration Verification of Sensitivity Test (CVOS), Practice Test, and True Blue Control Test [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms acquaintance test purposes, alternate names (Numbers Test, Demonstration Test, Stim Test, CVOS, etc.), and that it is not scored nor used for veracity testing.

As taught by the National Center for Credibility Assessment (NCCA), the acquaintance test is a form of the known-solution Peak of Tension (POT) test used to demonstrate the basic concepts of polygraph to an examinee [2]Verified Federal Psychophysiological Detection of Deception Examiner Handbook (NCCA/DoDPI)
Confirms ACQT is a form of known-solution Peak of Tension test as taught by NCCA, used to demonstrate basic concepts of polygraph to the examinee. The primary purpose is to assure the examinee that the polygraph process is effective for that individual [2]Verified Federal Psychophysiological Detection of Deception Examiner Handbook (NCCA/DoDPI)
Confirms ACQT is a form of known-solution Peak of Tension test as taught by NCCA, used to demonstrate basic concepts of polygraph to the examinee.

Think of it like a musician tuning an instrument before a performance. The polygraph measures subtle changes in breathing, sweat gland activity, cardiovascular responses, and sometimes muscular movement. Every person produces these responses at different intensities and baselines. Without this calibration step, the examiner would attempt to interpret your main test data without understanding your personal physiological norms.

The acquaintance test is not part of the scored examination [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms acquaintance test purposes, alternate names (Numbers Test, Demonstration Test, Stim Test, CVOS, etc.), and that it is not scored nor used for veracity testing. It does not contribute to a pass or fail determination. Its results are used exclusively to ensure the instrument and sensors are functioning properly and that the examiner can read your physiological patterns with confidence. If you are preparing for your polygraph, the acquaintance test will almost certainly be part of the process. You can book a polygraph test with a qualified examiner who follows these professional standards.

Where the Acquaintance Test Fits in the Overall Process

A complete polygraph examination follows a structured, multi-phase format. Understanding where the acquaintance test fits helps demystify the overall experience. The standard polygraph testing phases are:

Pre-test interview — The examiner explains the process, reviews the questions, obtains informed consent, and discusses the issues to be tested. The APA recommends that informed consent be obtained after an overview of the polygraph process, including instrumentation, sensors, and requirements for cooperating during testing [3]Verified APA Standards of Practice (Adopted August 23, 2019)
Confirms acquaintance test is mandatory under Section 1.7.5 for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations.

Acquaintance/stimulation test — The calibration phase described in this article.

In-test (chart collection) — The actual scored examination where relevant, comparison, and irrelevant questions are asked across multiple chart repetitions.

Post-test interview — The examiner reviews results and may discuss findings with the examinee.

The acquaintance test acts as the bridge between the conversational pre-test interview and the formal data collection. By the time you move into the scored portion of the exam, both you and the examiner have confirmed that the instrument is reading your responses correctly and that the sensors are properly attached. Understanding each phase can help reduce nervousness — learn more in our guide on whether you should be nervous about your polygraph test.

Instrument Calibration and Sensor Verification

The primary technical reason for the acquaintance test is calibration. A polygraph instrument typically monitors four to five physiological channels simultaneously: thoracic (upper chest) respiration, abdominal respiration, electrodermal activity (skin conductance), and cardiovascular measures via a blood pressure cuff or cardio monitor. Some modern systems also include a photoplethysmograph (PPG) sensor and motion-sensing pads. For more on how software has changed polygraph technology, see our digital revolution guide.

Each of these sensors must produce clean, readable data before the main test can begin. The acquaintance test gives the examiner a controlled opportunity to verify that all channels are functioning properly and that the sensitivity settings are appropriate for your individual physiology [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms acquaintance test purposes, alternate names (Numbers Test, Demonstration Test, Stim Test, CVOS, etc.), and that it is not scored nor used for veracity testing. Lafayette Instrument Company notes that for practical purposes, the acquaintance test serves as a de-facto functionality check for the polygraph system [4]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms the acquaintance test serves as a de-facto functionality check for polygraph instruments and describes procedures for documenting the ACQT.

For example, some examinees produce very strong electrodermal responses but subtle respiratory changes, while others show the reverse pattern. The examiner needs to identify this before interpreting your main test charts. You can learn more about the equipment and warranty considerations in our manufacturer comparison guide.

Demonstrating the Instrument's Capability

Perhaps equally important from a psychological standpoint, the acquaintance test demonstrates to you that the polygraph works. The National Research Council (2003) noted that stimulation tests are intended to strengthen in examinees the expectation that the polygraph can accurately determine the truthfulness of their answers [5]Verified The Polygraph and Lie Detection
Confirms stimulation tests are intended to strengthen examinee expectation of polygraph accuracy, and that research provides some support for the hypothesis that they improve detection accuracy. When the examiner correctly identifies which number you selected — even though you denied it — it provides a tangible demonstration that deception produces measurable physiological changes.

Research by Bradley and Janisse (1981), published in the journal Psychophysiology (volume 18, pages 307-315), studied the effects of accuracy demonstrations on the detection of deception using cardiovascular, electrodermal, and pupillary measures [6]Verified Accuracy Demonstrations, Threat, and the Detection of Deception: Cardiovascular, Electrodermal, and Pupillary Measures
Confirms that accuracy demonstrations (stimulation tests) can affect detection of deception using cardiovascular, electrodermal, and pupillary measures. The National Research Council cited this study as providing some support for the hypothesis that stimulation tests improve detection accuracy [5]Verified The Polygraph and Lie Detection
Confirms stimulation tests are intended to strengthen examinee expectation of polygraph accuracy, and that research provides some support for the hypothesis that they improve detection accuracy.

Nelson (2015) further confirmed that research by Kircher, Packard, Bell, and Bernhardt (2001) showed that the acquaintance test can contribute to increased test accuracy [7]Verified Scientific Basis for Polygraph Testing
Confirms acquaintance test should be conducted as part of standardized field practice, and that Kircher et al. (2001) showed it can contribute to increased test accuracy. This landmark study, commissioned by the U.S. Department of Defense Polygraph Institute, tested 336 participants in a mock crime experiment and examined whether stimulation pretests improve the accuracy of both probable-lie and directed-lie tests [8]Verified Effects of Prior Demonstrations of Polygraph Accuracy on Outcomes of Probable-Lie and Directed-Lie Polygraph Tests
Confirms the 336-participant mock crime experiment testing whether stimulation pretests improve accuracy of probable-lie and directed-lie tests.

A meta-analysis by Honts also suggests that between-chart stimulation offers a positive improvement in comparison question test (CQT) accuracy [9]Verified The Comparison Question Polygraph Test: A Contrast of Methods and Scoring
Confirms meta-analysis by Honts suggests between-chart stimulation offers positive improvement in CQT accuracy. The 1983 Office of Technology Assessment (OTA) review for the U.S. Congress likewise noted that stimulation tests are designed to increase differential responsivity between deceptive and nondeceptive subjects, and that some research suggests they increase the validity of polygraph examinations [10]Verified Scientific Validity of Polygraph Testing: A Research Review and Evaluation
Confirms stimulation tests are designed to increase differential responsivity and that some research suggests they increase validity of polygraph examinations.

Reducing Test Anxiety and Building Rapport

Anxiety is a universal part of taking a polygraph test, whether you are truthful or deceptive. The acquaintance test helps reduce some of this anxiety by giving you a practice run with the equipment. By the time you have completed it, you have already experienced what it feels like to sit with sensors attached, to hear the examiner ask questions, and to respond in the required yes-or-no format.

This familiarity reduces the novelty effect, which can otherwise create artificially elevated physiological responses on the first chart of the main test. For more on understanding how nervousness may affect your results, see our guide on the 9 factors that affect lie detector test results.

The acquaintance test also serves as a rapport-building tool. The interaction during this phase is low-stakes and collaborative — you and the examiner are working together to confirm the instrument is functioning. This collaborative dynamic can help ease the adversarial tension some examinees feel. Professional examiners understand that building rapport with the examinee is essential for obtaining valid results. If you are considering discussing a test with a partner, see our guide on how to tell your partner you want a lie detector test.

The Complete Procedure

While the specific format varies depending on the examiner's training and the polygraph technique being used, the general procedure follows a consistent pattern. According to the NCCA curriculum, the acquaintance test is conducted in a mini-polygraph examination format consisting of a pretest interview, data collection phase, data analysis phase, and post-test interview [2]Verified Federal Psychophysiological Detection of Deception Examiner Handbook (NCCA/DoDPI)
Confirms ACQT is a form of known-solution Peak of Tension test as taught by NCCA, used to demonstrate basic concepts of polygraph to the examinee.

Step 1: Sensor Attachment — The examiner attaches all polygraph sensors before the acquaintance test begins. This includes two pneumograph tubes (one around your upper chest, one around your abdomen), finger plates or electrodes for measuring skin conductance, a blood pressure cuff on your upper arm, and potentially a finger clip for pulse measurement. If a motion-sensing pad is used, you will be seated on it. Understanding respiratory suppression patterns can help you appreciate how breathing data contributes to the examination.

Step 2: Selection Phase — You are asked to select a number (typically between 2 and 6), a playing card, or another item from a defined set [11]Verified Validated Polygraph Techniques
Confirms Krapohl's (2006) review of validated polygraph techniques published in Polygraph, 35(3), and the standards for technique validation. In many cases, you write your selection on a piece of paper. The key is that one answer will be the lie — you know which one it is. A visual stimulus is used in the ACQT to ensure the examinee knows the sequence of the examination and the location of the selected key [2]Verified Federal Psychophysiological Detection of Deception Examiner Handbook (NCCA/DoDPI)
Confirms ACQT is a form of known-solution Peak of Tension test as taught by NCCA, used to demonstrate basic concepts of polygraph to the examinee.

Step 3: Question Presentation — The examiner asks a series of questions, one for each possible option. For example: "Did you write the number 1?" through "Did you write the number 7?" All questions are worded to elicit a "No" answer [2]Verified Federal Psychophysiological Detection of Deception Examiner Handbook (NCCA/DoDPI)
Confirms ACQT is a form of known-solution Peak of Tension test as taught by NCCA, used to demonstrate basic concepts of polygraph to the examinee. You answer "No" to every question, meaning you tell the truth on all answers except the one matching your selection.

Step 4: Physiological Recording — While you answer, the polygraph instrument records all physiological channels simultaneously. The examiner looks for a distinct response — typically a spike in electrodermal activity, a change in breathing pattern, or a blood pressure shift — at the moment you give your deceptive answer.

Step 5: Identification and Review — After the question series is complete, the examiner reviews the chart data and identifies which answer produced the strongest physiological response. The ACQT is not evaluated numerically but is analyzed using Peak of Tension test data analysis procedures [2]Verified Federal Psychophysiological Detection of Deception Examiner Handbook (NCCA/DoDPI)
Confirms ACQT is a form of known-solution Peak of Tension test as taught by NCCA, used to demonstrate basic concepts of polygraph to the examinee.

Step 6: Feedback and Adjustment — The examiner shares the result ("The instrument shows that you selected number 4. Is that correct?") to reinforce confidence in the process. If the data was unclear, the examiner may adjust sensor placement or sensitivity and repeat the acquaintance test.

Standard Formats Used in Professional Practice

There are several standard formats used for the acquaintance test. The APA Terminology Reference lists multiple recognized variants [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms acquaintance test purposes, alternate names (Numbers Test, Demonstration Test, Stim Test, CVOS, etc.), and that it is not scored nor used for veracity testing, and the one your examiner selects depends on their training background, the polygraph technique being employed, and the purpose of the examination.

The Number Test is the most common format. You select a number from a defined range (typically 2 through 6 to allow padding numbers before and after your selection), write it on a slip of paper, and then deny choosing each number as the examiner asks about them one by one from 1 through 7 [11]Verified Validated Polygraph Techniques
Confirms Krapohl's (2006) review of validated polygraph techniques published in Polygraph, 35(3), and the standards for technique validation. The OTA review confirmed that the number and card tests are the most common stim tests [10]Verified Scientific Validity of Polygraph Testing: A Research Review and Evaluation
Confirms stimulation tests are designed to increase differential responsivity and that some research suggests they increase validity of polygraph examinations. The simplicity of this format makes it ideal for nervous examinees.

The Card Test is one of the earliest forms of the stimulation test. You select a playing card from a small set, and the examiner presents each card verbally while you answer "No" to each question. While widely practiced in the early years of the polygraph profession, it has been partially replaced by other methods [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms acquaintance test purposes, alternate names (Numbers Test, Demonstration Test, Stim Test, CVOS, etc.), and that it is not scored nor used for veracity testing.

The Color Test is less commonly used and asks you to select a color from a set of swatches or cards. This format is sometimes employed when working with examinees who have limited literacy or language challenges.

The Surname Test is a newer variant described in recent literature. The subject is presented with a series of stimulus questions about their surname and instructed to answer incorrectly to the question that includes their actual surname [12]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms known-solution ACQT is better supported by evidence than unknown-solution variant, describes surname-based format, and reviews literature on acquaintance test procedures. Nelson, Prado, Blalock, and Handler (2018) provided detailed information on the history and use of this known-solution acquaintance test format [12]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms known-solution ACQT is better supported by evidence than unknown-solution variant, describes surname-based format, and reviews literature on acquaintance test procedures.

Regardless of the format, the underlying principle remains the same. Various polygraph examination techniques employ these acquaintance test variations, including the Backster Zone Comparison Test and the Federal Zone Comparison Technique.

Physiological Channels Recorded

During the acquaintance test, the same physiological channels that will be monitored in the main examination are actively recording data. Understanding what these channels measure helps you appreciate why the calibration step matters.

Respiratory Activity: Two pneumograph tubes monitor your breathing — one around the upper chest and one around the abdomen. When people lie, their breathing patterns often change in subtle but measurable ways: they may take a deeper breath before answering, hold their breath slightly, or experience a shift in breathing rate. Learn more about these patterns in our detailed guide to respiratory suppression in polygraph testing.

Electrodermal Activity (EDA): Metal plates or disposable adhesive electrodes attached to the fingers measure changes in skin conductance caused by sweat gland activity [13]Verified Polygraph Frequently Asked Questions
Confirms polygraph sensor types including finger electrodes for sweat gland activity, blood pressure cuff, finger plethysmograph, and motion sensors. Orienting responses — such as those triggered by recognition of a significant stimulus — have been shown to be accompanied by measurable physiological reactions, most prominently an increase in electrodermal activity [14]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms orienting responses are accompanied by measurable physiological reactions including changes in cardiovascular activity, respiration, and electrodermal activity. The electrodermal channel is often the most reactive during the acquaintance test.

Cardiovascular Activity: A blood pressure cuff on the upper arm or a cardio monitor records changes in blood pressure, heart rate, and blood volume. Some instruments also include a finger plethysmograph that monitors blood volume in a fingertip [13]Verified Polygraph Frequently Asked Questions
Confirms polygraph sensor types including finger electrodes for sweat gland activity, blood pressure cuff, finger plethysmograph, and motion sensors. Cardiovascular changes during deception can include increased heart rate and subtle blood pressure elevation.

Motion Detection: Many modern polygraph systems include motion-sensing pads placed in the examinee's chair. These sensors detect deliberate or involuntary physical movements that could indicate countermeasure attempts or artifacts that might interfere with test data.

Research from Polakowski, Kastek, and Pilski (2011) has even demonstrated the feasibility of using high-sensitivity thermal cameras to detect facial temperature changes during polygraph testing, achieving precision of less than 0.02°C [15]Verified Analysis of Facial Skin Temperature Changes in Acquaintance Comparison Question Test
Demonstrates feasibility of using high-sensitivity thermal cameras to detect facial temperature changes during polygraph testing with the acquaintance comparison question test format. While thermal imaging is not yet standard practice, it illustrates the expanding range of physiological indicators being explored.

The Key Distinction

One important distinction in professional practice is between known-solution and unknown-solution acquaintance tests. In a known-solution test, the examiner knows which number or item you selected — either because you showed them, wrote it on a visible paper, or the items were arranged so the answer is apparent. In an unknown-solution test, the examiner does not know the correct answer and must rely entirely on the physiological data to identify it.

The published literature provides stronger support for the known-solution ACQT than for the unknown-solution variant [12]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms known-solution ACQT is better supported by evidence than unknown-solution variant, describes surname-based format, and reviews literature on acquaintance test procedures. Nelson and colleagues noted that although studies have not supported a significant effect for the unknown-solution ACQT, the known-solution ACQT is better supported by scientific evidence [12]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms known-solution ACQT is better supported by evidence than unknown-solution variant, describes surname-based format, and reviews literature on acquaintance test procedures. Important advantages of the known-solution approach include that it does not engage a role-reversal — where the examinee is testing the polygraph rather than the other way around — and it does not rely on manipulation or deception as a form of demonstration [12]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms known-solution ACQT is better supported by evidence than unknown-solution variant, describes surname-based format, and reviews literature on acquaintance test procedures.

The known-solution format is now the preferred approach in many modern polygraph training programs, including those aligned with NCCA curriculum standards.

Practical Expectations

If you are about to take a polygraph examination, here is what the acquaintance test phase will feel like in practice. After the pre-test interview — during which the examiner explains the process, discusses the questions, and obtains your informed consent — you will be asked to sit in the examination chair.

The examiner will attach the polygraph sensors: two rubber tubes around your torso, finger electrodes or plates on your hand, and a blood pressure cuff on your arm. You may also sit on a motion-sensing pad. The equipment may feel slightly unusual but should not cause discomfort.

The examiner will explain the acquaintance test procedure clearly. You will be asked to select a number, typically by writing it on a piece of paper. The examiner will then ask a series of yes/no questions about which number you chose. You will answer "No" to every question, including the one that matches your selection — making that one response a deliberate lie.

After the series is complete, the examiner will review the chart data and identify which response you were deceptive on. When they correctly identify your number, it confirms that the instrument is reading your physiology accurately. This moment also demonstrates to you that the polygraph can detect physiological changes associated with deception.

The entire process typically takes 5 to 15 minutes. You will then proceed to the main examination. If you want to understand what happens if deception is detected during the actual test, see our guide on what happens if you lie on a polygraph.

Cognitive and Emotional Mechanisms

The acquaintance test leverages well-established psychological principles to enhance polygraph effectiveness. When you know the polygraph has accurately detected your single deceptive response during the acquaintance test, it activates a cognitive expectation that the instrument will also detect deception during the main examination. This heightened expectation increases the physiological differentiation between truthful and deceptive responses in the scored portion of the test.

The OTA review explained that stimulation tests are intended to reassure truthful subjects and provoke anxiety in deceptive subjects [10]Verified Scientific Validity of Polygraph Testing: A Research Review and Evaluation
Confirms stimulation tests are designed to increase differential responsivity and that some research suggests they increase validity of polygraph examinations. Their effect is to increase differential responsivity of deceptive and nondeceptive subjects to different questions on the examination [10]Verified Scientific Validity of Polygraph Testing: A Research Review and Evaluation
Confirms stimulation tests are designed to increase differential responsivity and that some research suggests they increase validity of polygraph examinations. For truthful examinees, the acquaintance test provides reassurance that the instrument can distinguish truth from deception, which reduces general anxiety and allows their truthful responses to remain relatively calm. For deceptive examinees, the demonstration heightens awareness that the instrument can detect lies, increasing physiological arousal during relevant questions.

This dual effect — calming the truthful while alerting the deceptive — is precisely what makes the acquaintance test such a valuable component of the examination process. The distinction between fiction and reality in polygraph testing is explored in our article on polygraph in crime novels.

Research has also explored whether nonverbal behavior during interrogation differs between truth-tellers and liars. Stromwall, Hartwig, and Granhag (2006) found that no differences in nonverbal behaviors distinguished liars from truth tellers during high-stakes police interrogations, despite liars experiencing greater internal stress [16]Verified To Act Truthfully: Nonverbal Behaviour and Strategies During a Police Interrogation
Found no differences in nonverbal behaviors distinguishing liars from truth tellers during high-stakes police interrogations, underscoring value of physiological measurement. This finding underscores why physiological measurement — rather than behavioral observation alone — remains the more reliable approach to credibility assessment.

Research Evidence on Accuracy Enhancement

Multiple studies have examined whether the acquaintance test improves the overall accuracy of polygraph examinations, and the evidence is encouraging.

Nelson (2015) noted that a practice test or acquaintance test should be conducted as part of standardized field practice, citing both the American Polygraph Association (2009) and the Department of Defense (2006) guidelines [7]Verified Scientific Basis for Polygraph Testing
Confirms acquaintance test should be conducted as part of standardized field practice, and that Kircher et al. (2001) showed it can contribute to increased test accuracy. He confirmed that research by Kircher, Packard, Bell, and Bernhardt (2001) has shown that this can contribute to increased test accuracy [7]Verified Scientific Basis for Polygraph Testing
Confirms acquaintance test should be conducted as part of standardized field practice, and that Kircher et al. (2001) showed it can contribute to increased test accuracy.

The Kircher et al. (2001) study was a comprehensive mock crime experiment conducted at the University of Utah with 336 participants, examining the effects of prior demonstrations of polygraph accuracy on both probable-lie and directed-lie polygraph tests [8]Verified Effects of Prior Demonstrations of Polygraph Accuracy on Outcomes of Probable-Lie and Directed-Lie Polygraph Tests
Confirms the 336-participant mock crime experiment testing whether stimulation pretests improve accuracy of probable-lie and directed-lie tests. This study was cited by the National Research Council's landmark 2003 report, The Polygraph and Lie Detection [5]Verified The Polygraph and Lie Detection
Confirms stimulation tests are intended to strengthen examinee expectation of polygraph accuracy, and that research provides some support for the hypothesis that they improve detection accuracy.

A meta-analysis by Honts also suggests that between-chart stimulation offers a positive improvement in CQT accuracy [9]Verified The Comparison Question Polygraph Test: A Contrast of Methods and Scoring
Confirms meta-analysis by Honts suggests between-chart stimulation offers positive improvement in CQT accuracy. When combined with a thorough pretest interview, between-chart discussion and stimulation produced higher accuracy rates, particularly for deceptive subjects [9]Verified The Comparison Question Polygraph Test: A Contrast of Methods and Scoring
Confirms meta-analysis by Honts suggests between-chart stimulation offers positive improvement in CQT accuracy.

The APA's own meta-analytic survey of validated polygraph techniques (2011) reported that event-specific (single-issue) diagnostic testing techniques produced an aggregated decision accuracy of 89%, with a confidence interval of 83% to 95% [17]Verified Polygraph Validity Research — Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms 89% decision accuracy for event-specific diagnostic testing and 87% combined accuracy for all validated techniques. The combination of all validated techniques produced a decision accuracy of 87%, with a confidence interval of 80% to 94% [17]Verified Polygraph Validity Research — Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms 89% decision accuracy for event-specific diagnostic testing and 87% combined accuracy for all validated techniques. These figures reflect examinations conducted in accordance with APA Standards of Practice, which mandate the acquaintance test as a required component.

Cullen and Bradley (2004) conducted additional research on control question positioning, finding that the order in which comparison and relevant questions are presented can affect differentiation between guilty and innocent participants [18]Verified Positions of Truthfully Answered Controls on Control Question Tests with the Polygraph
Demonstrated that control question positioning affects differentiation between guilty and innocent participants, highlighting importance of proper test structure. This work highlights the importance of proper test structure — including the calibration provided by the acquaintance test — in achieving reliable results.

Mandatory Standards for Examiners

The American Polygraph Association's Standards of Practice (adopted August 23, 2019) explicitly require the acquaintance test. Section 1.7.5 states: examiners shall conduct an acquaintance test for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations [3]Verified APA Standards of Practice (Adopted August 23, 2019)
Confirms acquaintance test is mandatory under Section 1.7.5 for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations. This is not optional guidance — it is a mandatory professional standard for all APA member examiners.

The APA Standards further specify that polygraph techniques for evidentiary examinations must demonstrate an unweighted average accuracy rate of 90% or greater in at least two published empirical studies [3]Verified APA Standards of Practice (Adopted August 23, 2019)
Confirms acquaintance test is mandatory under Section 1.7.5 for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations. For investigative testing, the threshold is 80% or greater [3]Verified APA Standards of Practice (Adopted August 23, 2019)
Confirms acquaintance test is mandatory under Section 1.7.5 for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations. Examinations must be scheduled for not less than 90 minutes [3]Verified APA Standards of Practice (Adopted August 23, 2019)
Confirms acquaintance test is mandatory under Section 1.7.5 for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations, and examiners shall not conduct more than four diagnostic or three evidentiary examinations in one day [3]Verified APA Standards of Practice (Adopted August 23, 2019)
Confirms acquaintance test is mandatory under Section 1.7.5 for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations.

The APA also requires that informed consent be obtained from the examinee after an overview of the polygraph process, including instrumentation, sensors, and requirements for cooperating during testing [3]Verified APA Standards of Practice (Adopted August 23, 2019)
Confirms acquaintance test is mandatory under Section 1.7.5 for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations. The acquaintance test serves as a natural extension of this informed consent process, giving the examinee a firsthand experience of the equipment before the scored examination begins.

To understand the broader standards framework, see our guide on APA forensic standards for polygraph examiners and learn about how the APA was founded.

Training and Certification Requirements

Professional polygraph training programs accredited by the APA include instruction on proper acquaintance test administration as part of their core curriculum. The NCCA (National Center for Credibility Assessment), which trains federal polygraph examiners, teaches the acquaintance test as a form of known-solution Peak of Tension test [2]Verified Federal Psychophysiological Detection of Deception Examiner Handbook (NCCA/DoDPI)
Confirms ACQT is a form of known-solution Peak of Tension test as taught by NCCA, used to demonstrate basic concepts of polygraph to the examinee.

Examiners who test sex offenders as a condition of treatment, probation, parole, or supervised release must have earned a specific certificate of training for this specialized work [3]Verified APA Standards of Practice (Adopted August 23, 2019)
Confirms acquaintance test is mandatory under Section 1.7.5 for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations. Programs like the PEAK CATC online polygraph training and the PEAK interviewing course teach modern approaches to acquaintance test administration alongside other examination components.

Krapohl's (2006) review of validated polygraph techniques, published in Polygraph (volume 35, issue 3), established criteria for what constitutes a validated technique [11]Verified Validated Polygraph Techniques
Confirms Krapohl's (2006) review of validated polygraph techniques published in Polygraph, 35(3), and the standards for technique validation. These standards have shaped how acquaintance tests are integrated into examination protocols across the profession.

Addressing Examinee Worries

Many examinees express concerns about the acquaintance test that are based on misconceptions. Here are the most common:

Myth: The acquaintance test is part of the scored examination. Fact: The acquaintance test is explicitly not scored and is not used for veracity testing [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms acquaintance test purposes, alternate names (Numbers Test, Demonstration Test, Stim Test, CVOS, etc.), and that it is not scored nor used for veracity testing. It has no bearing on your pass/fail result.

Myth: If the examiner cannot identify your number, you will fail the test. Fact: If the acquaintance test produces unclear results, the examiner will adjust the sensors and repeat the procedure. It is a calibration step, not a pass/fail determination.

Myth: The examiner uses tricks to identify your number. Fact: In the known-solution format — which is the best-supported approach — the examiner may already know your selection. The purpose is not to trick you but to calibrate the instrument and demonstrate the process [12]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms known-solution ACQT is better supported by evidence than unknown-solution variant, describes surname-based format, and reviews literature on acquaintance test procedures. The known-solution approach avoids manipulation or deception in the demonstration [12]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms known-solution ACQT is better supported by evidence than unknown-solution variant, describes surname-based format, and reviews literature on acquaintance test procedures.

Myth: Nervous people always fail the acquaintance test. Fact: Some nervousness is normal and expected. The acquaintance test actually helps reduce nervousness for the main examination by familiarizing you with the equipment and process.

Myth: You can use the acquaintance test to practice beating the polygraph. Fact: The acquaintance test actually helps examiners detect countermeasure attempts [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms acquaintance test purposes, alternate names (Numbers Test, Demonstration Test, Stim Test, CVOS, etc.), and that it is not scored nor used for veracity testing. Movement sensors and careful observation during this phase can reveal if someone is trying to manipulate their responses.

If you are concerned about a potential polygraph examination disqualification, understanding the acquaintance test can help set realistic expectations.

Evolution of the Stimulation Test

The use of stimulation tests in polygraph examinations has a long history dating back to the early decades of the profession. The card test was one of the earliest formats, and its use in field polygraph examinations was documented extensively by the 1970s and 1980s [10]Verified Scientific Validity of Polygraph Testing: A Research Review and Evaluation
Confirms stimulation tests are designed to increase differential responsivity and that some research suggests they increase validity of polygraph examinations. The OTA's 1983 review for the U.S. Congress described stimulation tests as a standard component of field polygraph practice [10]Verified Scientific Validity of Polygraph Testing: A Research Review and Evaluation
Confirms stimulation tests are designed to increase differential responsivity and that some research suggests they increase validity of polygraph examinations.

Stanley Abrams addressed polygraph test procedures, including the stimulation phase, in his landmark book The Complete Polygraph Handbook, published by Lexington Books in 1989 [19]Verified The Complete Polygraph Handbook
Confirmed reference work covering polygraph test procedures, techniques, scoring, validity, and the roles of pretest phases including stimulation tests. This text became a standard reference for polygraph professionals and covered techniques, scoring, validity, and the roles of pretest procedures.

The evolution from unknown-solution formats to known-solution formats represents a significant advancement in professional practice. Handler and Nelson (2007) contributed to modernizing polygraph terminology in their article "Polygraph Terms for the 21st Century" in the journal Polygraph [20]Verified Polygraph Terms for the 21st Century
Confirms Handler and Nelson's contributions to modernizing polygraph terminology including acquaintance test nomenclature. The 4th edition of the APA Terminology Reference (2022), co-authored by Krapohl, Handler, and Lynch, provides the most current standardized definitions [1]Verified Terminology Reference for the Science of Psychophysiological Detection of Deception (4th Edition, 2022)
Confirms acquaintance test purposes, alternate names (Numbers Test, Demonstration Test, Stim Test, CVOS, etc.), and that it is not scored nor used for veracity testing.

Historically, polygraph testing gained significant momentum during the post-war era of the 1940s, and the acquaintance test evolved alongside broader improvements in examination methodology.

New Technologies and Approaches

Ongoing research continues to explore how supplementary technologies might enhance the acquaintance test and the broader polygraph examination process. Polakowski, Kastek, and Pilski (2011) demonstrated the feasibility of using high-sensitivity thermal cameras to detect facial temperature changes during polygraph testing with the acquaintance comparison question test format [15]Verified Analysis of Facial Skin Temperature Changes in Acquaintance Comparison Question Test
Demonstrates feasibility of using high-sensitivity thermal cameras to detect facial temperature changes during polygraph testing with the acquaintance comparison question test format. Their research achieved precision of less than 0.02°C, suggesting that thermal imaging could serve as an additional physiological channel in future examinations.

Dalski, Kovacs, Wiese, and Ambrus (2022) investigated the shared signals of face familiarity, examining long-term acquaintance, voluntary control, and concealed knowledge [21]Verified Characterizing the Shared Signals of Face Familiarity: Long-term Acquaintance, Voluntary Control, and Concealed Knowledge
Research relevant to understanding how recognition and familiarity manifest physiologically — processes related to the Peak of Tension format used in acquaintance testing. This research contributes to understanding how recognition and familiarity manifest physiologically — processes directly relevant to the Peak of Tension format used in acquaintance testing.

Alternative credibility assessment technologies, such as voice stress detection (CVSA), have been proposed as competitors to polygraph testing. However, the APA has noted that instruments claiming to record voice stress have not been shown to work any better than chance [13]Verified Polygraph Frequently Asked Questions
Confirms polygraph sensor types including finger electrodes for sweat gland activity, blood pressure cuff, finger plethysmograph, and motion sensors. The polygraph acquaintance test, by contrast, has a well-documented evidence base supporting its use.

Future developments may include more sophisticated computer-assisted analysis of acquaintance test data, potentially using algorithms like the Objective Scoring System (OSS-3) that are already used for the main examination [7]Verified Scientific Basis for Polygraph Testing
Confirms acquaintance test should be conducted as part of standardized field practice, and that Kircher et al. (2001) showed it can contribute to increased test accuracy.