Stimulation Test vs. Acquaintance Test in Polygraph

The Two Procedures That Prepare You for the Polygraph

Before the formal questioning phase of any polygraph examination, most examiners conduct a preliminary procedure designed to help the examinee become comfortable with the process. Depending on the examiner's training, the validated technique being used, and the context of the test, this preliminary step may be called a stimulation test (often shortened to "stim test"), an acquaintance test, or sometimes both terms together.

According to the official PDD Terminology Reference published by the APA, 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 [3]Verified PDD Terminology Reference for the Science of Psychophysiological Detection of Deception
Confirms acquaintance test definition, purposes, and lists multiple synonymous terms including stimulation test, numbers test, and demonstration test. The reference further lists multiple terms used for this family of procedures, including Numbers Test, Demonstration Test, Stimulation (Stim) Test, Practice Test, Blind Numbers Test, Calibration Verification of Sensitivity Test (CVOS), and True Blue Control Test [3]Verified PDD Terminology Reference for the Science of Psychophysiological Detection of Deception
Confirms acquaintance test definition, purposes, and lists multiple synonymous terms including stimulation test, numbers test, and demonstration test.

The APA Standards of Practice (effective August 23, 2024) explicitly state: "Examiners shall conduct an acquaintance test for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations" [2]Verified APA Standards of Practice
Confirms APA requirement that examiners shall conduct an acquaintance test for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations (effective 08/23/2024). This makes the acquaintance test a mandatory component of professional polygraph practice, not an optional step.

To understand these procedures fully, it helps to place them within the larger framework of a complete polygraph examination. A standard exam includes a pretest interview, sensor attachment, question review, the demonstration phase (where stim and acquaintance tests occur), multiple chart collection runs, scoring, and a post-test interview. The demonstration phase is the examinee's first direct experience of the polygraph recording their physiological responses, and it sets the psychological tone for everything that follows.

What Exactly Is a Stimulation Test?

A stimulation test — commonly called a "stim test" — is a pre-test demonstration procedure designed primarily to convince the examinee that the polygraph instrument can accurately detect deception. The word "stimulation" in this context refers to the psychological stimulation of the examinee's belief system: the examiner is actively building the examinee's confidence (or concern) that the instrument will catch them if they lie.

The most common format is the known-lie card or number test. The examinee selects a card from a deck or chooses a number within a specific range. The examiner then asks the examinee to deny choosing the correct item — effectively requiring them to lie on one specific question. After recording physiological responses throughout the question series, the examiner identifies the correct card or number, demonstrating to the examinee that their deception was detected [4]Verified Scientific Validity of Polygraph Testing: A Research Review and Evaluation
Confirms stimulation tests are designed to convince subjects of polygraph accuracy and that research suggests they increase test validity.

As the Office of Technology Assessment's review of polygraph science confirmed, stimulation tests are designed to further convince subjects of the accuracy of the polygraph examination, and some research suggests stimulation tests increase the validity of polygraph examinations [4]Verified Scientific Validity of Polygraph Testing: A Research Review and Evaluation
Confirms stimulation tests are designed to convince subjects of polygraph accuracy and that research suggests they increase test validity.

Historical Origins of the Stim Test

The stimulation test has roots stretching back to the earliest days of modern polygraph testing. Leonarde Keeler, who moved to Chicago in 1930 to work at the Scientific Crime Detection Laboratory at Northwestern University [5]Verified Leonarde Keeler — Wikipedia
Confirms Keeler moved to Chicago in 1930 to work at the Scientific Crime Detection Laboratory at Northwestern University and became head of the laboratory in 1936, is widely recognized as a pioneer of early demonstration techniques. Keeler ultimately became head of the laboratory in 1936 [5]Verified Leonarde Keeler — Wikipedia
Confirms Keeler moved to Chicago in 1930 to work at the Scientific Crime Detection Laboratory at Northwestern University and became head of the laboratory in 1936. A UC Berkeley article describes how one of his trademark methods was the "card trick" test — where a subject picked a playing card and was instructed to deny having chosen each one, forcing a lie that the polygraph would detect [6]Verified He Met His Wife Over a Lie Detector — PBS American Experience
Confirms Keeler's card trick test as a trademark method and predecessor of the modern stimulation test. Keeler, who was described as "always something of an amateur magician," often used marked cards to ensure he could identify the correct one [6]Verified He Met His Wife Over a Lie Detector — PBS American Experience
Confirms Keeler's card trick test as a trademark method and predecessor of the modern stimulation test.

Keeler's promotional demonstrations helped establish the polygraph as a legitimate investigative tool in law enforcement [7]Verified Biography of Leonarde Keeler
Confirms Keeler introduced the polygraph to U.S. law enforcement and his contributions to establishing polygraph in criminal investigation. For more on Keeler's contributions, see our article on the Keeler Polygraph systems and our comprehensive history of polygraphs and law enforcement.

The stimulation test concept was later formalized by Cleve Backster, who developed the Backster Zone Comparison Technique (ZCT). Backster received training from Leonarde Keeler and became director of the Keeler Polygraph Institute in Chicago after Keeler's death [8]Verified Cleve Backster — Psi Encyclopedia
Confirms Backster received training from Keeler, became director of the Keeler Polygraph Institute after Keeler's death, and founded the Backster School of Lie Detection and Research Foundation. He later returned to New York and founded what would eventually become the Backster School of Lie Detection [8]Verified Cleve Backster — Psi Encyclopedia
Confirms Backster received training from Keeler, became director of the Keeler Polygraph Institute after Keeler's death, and founded the Backster School of Lie Detection and Research Foundation. In 1965, he established the Backster Research Foundation [8]Verified Cleve Backster — Psi Encyclopedia
Confirms Backster received training from Keeler, became director of the Keeler Polygraph Institute after Keeler's death, and founded the Backster School of Lie Detection and Research Foundation. His 1969 publication, "Technique Fundamentals of the Tri-Zone Polygraph Test" (New York: Backster Research Foundation), formally documented the integration of the stim test into the zone comparison framework [9]Verified Technique Fundamentals of the Tri-Zone Polygraph Test
Confirms Backster (1969) publication 'Technique fundamentals of the Tri-Zone Polygraph Test' published by Backster Research Foundation, New York. Backster's Zone Comparison Technique was the first polygraph interpretation system to use a numerical evaluation and remains widely used today [8]Verified Cleve Backster — Psi Encyclopedia
Confirms Backster received training from Keeler, became director of the Keeler Polygraph Institute after Keeler's death, and founded the Backster School of Lie Detection and Research Foundation.

John E. Reid, another foundational figure in polygraph science, also incorporated stimulation elements into his Control Question Technique. The National Research Council (2003) noted that the Reid technique included the use of a stimulation test between the first and second presentations of the questions [10]Verified The Polygraph and Lie Detection
Confirms the use of stimulation tests in standard polygraph techniques including the Reid and Backster methods. For a deeper understanding of comparison questions in polygraph testing, see our dedicated guide.

Types of Stimulation Tests

While the known-lie card test is the most widely recognized format, several variations exist in professional practice:

Number card test: The examinee picks a number from a set range (commonly 1 through 7). The examiner asks about each number; the examinee denies all of them. The examiner identifies the correct number from the chart data.

Known-solution test: The examiner already knows which card or number the examinee selected (through a covert method or pre-arrangement) and uses this knowledge to ensure a successful demonstration [11]Verified Comparison of Two Stimulation Tests and Their Effect on the Polygraph Technique
Confirms research comparing known card test and standard card test formats in stimulation test procedures.

Blind number test: The examiner genuinely does not know the answer and must identify it solely from the chart data. This format carries greater risk — if the examiner identifies the wrong number, it can undermine the examinee's confidence rather than build it.

Known-solution acquaintance test using surname: As described by Nelson, Prado, Blalock and Handler (2018), this format presents the examinee with a series of stimulus questions about their surname, instructing them to answer incorrectly to the question that includes their actual surname [12]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms acquaintance test is part of virtually every polygraph exam and serves as a form of functionality check.

Modified stim procedures: Some modern techniques use abbreviated stimulation formats integrated into the pre-test discussion rather than run as a formal separate test.

What Is an Acquaintance Test?

An acquaintance test is a preliminary run-through designed primarily to familiarize the examinee with the physical experience of being connected to the polygraph and answering questions while their physiological responses are being recorded. The PDD Terminology Reference defines the acquaintance test as a testing procedure conducted as the first chart, which is designed to assess an examinee's capability to process information, detect psychological or chemical countermeasures, permit adjustment of gain settings to match the response capability of the examinee, determine whether sufficient professional rapport has been established, and reduce excessive anxiety [3]Verified PDD Terminology Reference for the Science of Psychophysiological Detection of Deception
Confirms acquaintance test definition, purposes, and lists multiple synonymous terms including stimulation test, numbers test, and demonstration test.

The Department of Defense Polygraph Institute described the acquaintance test as a standard known-solution numbers test whose purposes include: demonstrating the examination process to the examinee, allowing the examinee to become accustomed to the components and procedures, allowing the examiner to adjust the instrument, and making sure the examinee is physiologically capable of responding when lying [13]Verified The Lying Game: National Security and the Test for Espionage and Sabotage
Confirms DoDPI definition and purposes of the acquaintance test including demonstration, familiarization, instrument adjustment, and responsiveness verification.

Nelson et al. (2018) emphasized that the routine acquaintance test is a part of virtually every polygraph exam and is, for practical purposes, a form of functionality check for the polygraph instrument [12]Verified Practical Polygraph: The Known-Solution Acquaintance Test and Functionality Check
Confirms acquaintance test is part of virtually every polygraph exam and serves as a form of functionality check. This dual-purpose nature — serving both the examinee and the examiner — makes the acquaintance test an essential component of the examination process.

The Practical Functions of the Acquaintance Test

The acquaintance test serves several important practical functions that extend beyond mere familiarization:

Sensor verification: The examiner confirms that all physiological channels — respiration (pneumograph), electrodermal activity (EDA/GSR), cardiovascular (cardiosphygmograph), and any supplemental channels — are recording clean, interpretable data. Research by Anastasova et al. (2018) demonstrated that even factors such as nail polish can affect the quality of photoplethysmograph signals in polygraph examinations, highlighting the importance of thorough sensor verification during this phase [14]Verified Differences in the Quality of the Photoplethysmograph Signal in Subjects with and without Nail Polish
Confirms nail polish affects photoplethysmograph signal quality, supporting importance of standardized pre-test sensor verification during acquaintance testing. For more on the sensors used in modern systems, see our Stoelting CPS II Polygraph System review.

Baseline observation: The examiner gets an early look at the examinee's baseline physiological patterns, including normal breathing rate, heart rate variability, and electrodermal responsiveness. For more on this process, see our guide to what a polygraph baseline test is and how it works.

Examinee comfort: Many people have never been connected to a polygraph before. The acquaintance test lets them experience the sensation of the sensors, the feel of the blood pressure cuff inflating, and the rhythm of the question-and-answer format without the pressure of actual test questions. Our guide on 5 things to know before a lie detector test covers this familiarization process from the examinee's perspective.

Procedural training: The examinee learns how to sit still, breathe naturally, answer questions with a clear "yes" or "no," and follow the examiner's instructions during chart collection.

Artifact identification: The examiner can identify and address any artifacts in the chart data — such as movement artifacts, deep sighs, or irregular breathing patterns — before the actual test begins. Individual differences in psychological responses can significantly affect test data, as Phillips and Vendemia (2008) found that individual psychological differences significantly affect comparison question anxiety levels [15]Verified Individual Differences in Comparison Question Anxiety
Confirms individual psychological differences significantly affect comparison question anxiety levels, impacting test validity.

Countermeasure detection: The acquaintance test gives the examiner an early opportunity to observe whether the examinee may be attempting to manipulate their responses. For more on this topic, see our guide on whether you can beat a polygraph if guilty.

Primary Purpose, Format, and Psychological Effect

While both procedures occupy the same slot in the examination timeline, they differ in important ways:

Primary Purpose — Stim test: Demonstrates instrument accuracy to build examinee belief that deception will be detected. Acquaintance test: Familiarizes the examinee with the physical process and helps them feel comfortable with the equipment and format.

Format — Stim test: Typically involves a known-lie card test or number test where deception is deliberately introduced. Acquaintance test: Uses simple, known-answer questions with the examinee instructed to lie to one specific item (such as their surname), though no scoring is performed.

Psychological Effect — Stim test: Increases the emotional salience of the test by demonstrating the instrument's detection capability, creating heightened physiological arousal during relevant questions. This connects to the fundamental principle that an examinee who believes the polygraph works will produce more diagnostically useful physiological data [6]Verified He Met His Wife Over a Lie Detector — PBS American Experience
Confirms Keeler's card trick test as a trademark method and predecessor of the modern stimulation test. Acquaintance test: Reduces anxiety by normalizing the process and letting the examinee experience the sensors in a low-stakes setting.

Deception Component — Stim test: Requires the examinee to deliberately lie to at least one question (the known-lie item). Acquaintance test: Also involves a known-lie element, but the primary purpose is familiarization rather than demonstration.

Examiner Feedback — Stim test: The examiner reveals the result (identifying the chosen card or number) as a critical demonstration step. Acquaintance test: Results may or may not be revealed, as the feedback focuses on process comfort and sensor readiness.

Duration — Stim test: Typically 5-10 minutes. Acquaintance test: Typically 3-5 minutes.

The role of the polygraph examiner is central to both procedures — a skilled examiner uses these tests to calibrate both the instrument and the examinee's psychological readiness.

Why the Terms Are So Often Used Interchangeably

Despite their different primary objectives, stimulation tests and acquaintance tests share several important characteristics. As one academic review of polygraph methodology noted, the examiner may perform a demonstration of the polygraph's accuracy, commonly referred to as a stimulation or acquaintance test — using the terms as direct synonyms [16]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms the examiner may perform a demonstration commonly referred to as a stimulation or acquaintance test, published in Crime Psychology Review Vol. 1, No. 1, pp. 59-83.

Both occur during the pre-test phase: They happen after sensor attachment but before formal chart collection begins.

Both are non-scored: Neither procedure contributes to the final diagnostic opinion.

Both involve sensor recording: The polygraph instrument is actively recording all physiological channels during both procedures.

Both serve an educational function: Whether demonstrating accuracy or familiarizing the examinee, both procedures reduce uncertainty about what the test experience will feel like.

Both build examiner-examinee rapport: The interaction during these procedures helps establish the professional relationship that supports accurate chart collection. Understanding how the pretest interview and these procedures work together is essential for examinees.

Both involve a known-lie element: In both procedures, the examinee is instructed to answer one question untruthfully, providing a reference response.

The substantial overlap between these procedures helps explain why the PDD Terminology Reference lists them under the same entry, with the stimulation test listed as a synonym for the acquaintance test [3]Verified PDD Terminology Reference for the Science of Psychophysiological Detection of Deception
Confirms acquaintance test definition, purposes, and lists multiple synonymous terms including stimulation test, numbers test, and demonstration test.

How Belief in the Instrument Affects Test Results

The psychological underpinning of the stimulation test rests on a well-established principle in psychophysiological detection of deception: an examinee who believes the polygraph can detect their lies will produce stronger, more differentiated physiological responses to relevant questions than one who is skeptical of the instrument. This concept traces directly to Keeler's original insight — as the Berkeley article noted about his card trick demonstrations, it was a means to an end: the better the examiner convinced the test subject that the machine could pick out the lies, the more dramatic the results would be [6]Verified He Met His Wife Over a Lie Detector — PBS American Experience
Confirms Keeler's card trick test as a trademark method and predecessor of the modern stimulation test.

Research by Widacki (2009) provided quantitative support for this principle. His study found that in 63% of deceptive subjects, reactions to critical questions were greater in the control question test administered after the stimulation test compared to before [1]Verified When Should the Polygraph Stimulation Number Test be Performed?
Confirms that in 63% of deceptive subjects, reactions to critical questions were greater after the stimulation test, published in European Polygraph Vol. 3, No. 2 (2009). This finding challenges the assumption that stimulation testing merely reduces reactions, and instead supports the view that a well-conducted stim test enhances the diagnostically useful differentiation between relevant and comparison question responses.

Matte (2012) further examined how stimulation test timing influences examinee psychological set and physiological response patterns to relevant and comparison questions across multiple chart positions [17]Verified Effect of the Stimulation Test Administered Before and After the First Relevant Chart of the Control Question Test
Confirms research examining how stimulation test timing influences examinee psychological set and physiological response patterns, published in European Polygraph Vol. 6, No. 3(21), pp. 193-203. His research in European Polygraph highlighted the importance of when the stim test is administered relative to the first relevant chart, with implications for optimal test design.

The acquaintance test operates through a complementary but distinct psychological mechanism. By reducing the novelty and uncertainty of the testing experience, the acquaintance test helps the examinee settle into a more natural physiological baseline. This normalization means that the physiological responses recorded during the subsequent formal test are more likely to reflect genuine psychological reactions to question content rather than generalized anxiety about the unfamiliar testing situation. Understanding how sleep deprivation and other factors can affect baseline states further underscores the importance of this normalization process.

What the Research Shows

The impact of stimulation and acquaintance tests on overall polygraph accuracy has been studied through both direct experimentation and meta-analytic reviews.

The APA's comprehensive meta-analytic survey found that validated PDD techniques produce an aggregated decision accuracy of 87% (with a confidence interval of 80%-94%) and an inconclusive rate of 13% [18]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms validated PDD techniques produce 87% aggregated decision accuracy (CI 80%-94%), 89% for single-issue diagnostic testing (CI 83%-95%), based on 38 studies with 3,723 examinations. For single-issue diagnostic testing, decision accuracy was even higher at 89% (confidence interval of 83%-95%), with an estimated inconclusive rate of 11% [18]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms validated PDD techniques produce 87% aggregated decision accuracy (CI 80%-94%), 89% for single-issue diagnostic testing (CI 83%-95%), based on 38 studies with 3,723 examinations. These results were based on 38 studies involving 32 different samples and 45 different experiments, with 295 scorers providing 11,737 scored results from 3,723 examinations [18]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms validated PDD techniques produce 87% aggregated decision accuracy (CI 80%-94%), 89% for single-issue diagnostic testing (CI 83%-95%), based on 38 studies with 3,723 examinations. While these figures reflect the accuracy of validated techniques as a whole, the stimulation and acquaintance tests are integral procedural components of those validated techniques.

Honts and Reavy (2009) examined the effects of comparison question type and between-test stimulation on the validity of the comparison question test. Their study found a significant positive effect for between-repetition stimulation, reflecting an increased number of true positive outcomes when stimulation was employed [19]Verified Effects of Comparison Question Type and Between Test Stimulation on the Validity of Comparison Question Test
Confirms significant positive effect of between-repetition stimulation on comparison question test validity, recommending adoption in field practice. The study recommended the adoption of between-chart stimulation in field practice [19]Verified Effects of Comparison Question Type and Between Test Stimulation on the Validity of Comparison Question Test
Confirms significant positive effect of between-repetition stimulation on comparison question test validity, recommending adoption in field practice.

A comprehensive meta-analysis of the comparison question test by Honts et al. (2021) in Applied Cognitive Psychology, which analyzed 138 datasets, concluded that the CQT can be accurate, that experimental studies are generalizable, and no publication bias was detected [20]Verified A Comprehensive Meta-Analysis of the Comparison Question Polygraph Test
Confirms CQT can be accurate with 138 datasets analyzed, motivation positively related to accuracy, no publication bias detected. Their results showed that level of motivation had a positive linear relationship with accuracy measures — a finding consistent with the psychological principles underlying stimulation tests [20]Verified A Comprehensive Meta-Analysis of the Comparison Question Polygraph Test
Confirms CQT can be accurate with 138 datasets analyzed, motivation positively related to accuracy, no publication bias detected.

Nelson, Krapohl, and Handler (2008) conducted a Monte Carlo comparison study of the OSS-3 and human polygraph scorers, published in Polygraph, Vol. 37(3), demonstrating that computer algorithms can meet or exceed human experts in polygraph decision-making, providing perfect reliability [21]Verified Brute-Force Comparison: A Monte Carlo Study of the Objective Scoring System version 3 (OSS-3) and Human Polygraph Scorers
Confirms Monte Carlo study comparing OSS-3 algorithm accuracy to human examiners, published in Polygraph Vol. 37(3), pp. 185-215. This research underscores the precision achievable when pre-test procedures — including acquaintance and stimulation tests — are properly conducted as part of a validated technique.

For an in-depth look at how science has evaluated polygraph testing, see our guide on the NRC 2003 Report.

What the Standards Mandate

The APA Standards of Practice (effective August 23, 2024) establish clear requirements for the acquaintance test in professional polygraph practice. Section 1.7.6 states: "Examiners shall conduct an acquaintance test for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations" [2]Verified APA Standards of Practice
Confirms APA requirement that examiners shall conduct an acquaintance test for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations (effective 08/23/2024). This mandatory requirement applies to all APA member examiners and reflects the profession's recognition of the acquaintance test's essential role in producing valid, reliable test results.

The standards also require that examinations use evidence-based validated testing techniques [2]Verified APA Standards of Practice
Confirms APA requirement that examiners shall conduct an acquaintance test for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations (effective 08/23/2024). Since the acquaintance test is a required component of virtually all validated techniques, omitting it would constitute a deviation from validated protocol. The standards further require that questions used in the assessment of truth and deception shall be followed by time intervals of not less than 20 seconds from question onset to question onset [2]Verified APA Standards of Practice
Confirms APA requirement that examiners shall conduct an acquaintance test for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations (effective 08/23/2024), and that examinations shall be scheduled for not less than 90 minutes [2]Verified APA Standards of Practice
Confirms APA requirement that examiners shall conduct an acquaintance test for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations (effective 08/23/2024).

For examiners seeking to stay current with professional requirements, our guide on polygraph examiner continuing education covers what counts toward maintaining credentials. The APA also requires that all phases of the exam be recorded via audio or audio-video, maintained for a minimum of one year [2]Verified APA Standards of Practice
Confirms APA requirement that examiners shall conduct an acquaintance test for all diagnostic, evidentiary, paired-testing, initial screening, and initial investigative examinations (effective 08/23/2024).

The requirement for validated techniques also means examiners should be familiar with the full list of APA validated polygraph techniques and how the acquaintance or stimulation test fits within each protocol.

Thermal Imaging, Brain Stimulation, and Stimulus Research

Recent research has extended the study of acquaintance and stimulation procedures into new technological domains.

Polakowski, Kastek, and Pilski (2011) demonstrated the feasibility of using high-sensitivity thermal cameras to detect facial temperature changes during polygraph testing with precision of less than 0.02°C [22]Verified Analysis of Facial Skin Temperature Changes in Acquaintance Comparison Question Test
Confirms feasibility of using high-sensitivity thermal cameras to detect facial temperature changes during polygraph testing with precision of less than 0.02°C. Their study, published in European Polygraph, specifically examined temperature changes during an acquaintance comparison question test, opening possibilities for supplementing traditional polygraph channels with thermal data.

Anastasova et al. (2018) published the first study examining the effects of nail polish on photoplethysmograph signal quality in polygraph settings, finding that nail polish can significantly impact signal quality — a practical finding directly relevant to the sensor verification function of the acquaintance test [14]Verified Differences in the Quality of the Photoplethysmograph Signal in Subjects with and without Nail Polish
Confirms nail polish affects photoplethysmograph signal quality, supporting importance of standardized pre-test sensor verification during acquaintance testing.

Matte (2018) detailed how the Matte Quadri-Track Zone Comparison Technique (MQTZCT) introduced substantive innovations distinguishing it from Backster's original technique, including lower truth cut-off scores and Fear/Hope of Error questions addressing the Othello Error [23]Verified Setting the Record Concerning the Differences Between the Matte Quadri-Track and the Backster Zone Comparison Techniques
Confirms MQTZCT innovations including lower truth cut-off scores and Fear/Hope of Error questions addressing the Othello Error, published in European Polygraph Vol. 12, No. 3(45). The MQTZCT notably uses the stimulation test as an integral component, in contrast to Backster's later rejection of its use [23]Verified Setting the Record Concerning the Differences Between the Matte Quadri-Track and the Backster Zone Comparison Techniques
Confirms MQTZCT innovations including lower truth cut-off scores and Fear/Hope of Error questions addressing the Othello Error, published in European Polygraph Vol. 12, No. 3(45).

Research into stimulus presentation methods has also advanced. Fumagalli, Synnott, and Ioannou (2022) found that visual stimulus presentation produced significantly higher Concealed Information Test detection rates compared to auditory presentation, with large effect sizes (d=7.35, p<.005) [24]Verified Verbal vs Visual Stimulation Using the Concealed Information Test
Confirms visual stimulus presentation produced significantly higher CIT detection rates with large effect sizes (d=7.35, p<.005). This finding has implications for how stimulation tests might be optimized in future practice.

Brain stimulation research has explored the neural mechanisms underlying deception detection. Sowden et al. (2015) found that electrical stimulation of the right temporoparietal junction significantly improved lie detection performance (p=0.009) [25]Verified Transcranial Current Stimulation of the Temporoparietal Junction Improves Lie Detection
Confirms electrical stimulation of the right temporoparietal junction significantly improved lie detection performance (p=0.009), while Verschuere, Schuhmann, and Sack (2012) investigated the role of the inferior frontal sulcus in deception using transcranial magnetic stimulation [26]Verified Does the Inferior Frontal Sulcus Play a Functional Role in Deception? A Neuronavigated Theta-Burst Transcranial Magnetic Stimulation Study
Foundational research investigating neural mechanisms of deception using transcranial magnetic stimulation. Luber et al. (2009) examined the ethical and scientific challenges of using non-invasive brain stimulation in deception detection [27]Verified Non-Invasive Brain Stimulation in the Detection of Deception: Scientific Challenges and Ethical Consequences
Examines scientific challenges and ethical issues of brain stimulation in deception detection. These studies, while distinct from traditional polygraph stimulation tests, illuminate the broader neural science of deception detection.

Dalski et al. (2022) characterized the shared signals of face familiarity, examining long-term acquaintance, voluntary control, and concealed knowledge [28]Verified Characterizing the Shared Signals of Face Familiarity: Long-Term Acquaintance, Voluntary Control, and Concealed Knowledge
Foundational research on cognitive processes of familiarity and concealed knowledge relevant to acquaintance testing — research that may have future implications for understanding the cognitive processes engaged during acquaintance testing procedures.

Best Practices for Conducting Both Procedures

For polygraph examiners, the effective administration of stimulation and acquaintance tests requires attention to several practical considerations.

Timing: Most validated techniques specify when the stimulation or acquaintance test should occur within the examination sequence. Some techniques call for the stim test before the first relevant chart, while others position it between the first and second charts. Matte's (2012) research specifically examined the effects of this timing decision [17]Verified Effect of the Stimulation Test Administered Before and After the First Relevant Chart of the Control Question Test
Confirms research examining how stimulation test timing influences examinee psychological set and physiological response patterns, published in European Polygraph Vol. 6, No. 3(21), pp. 193-203, and examiners should follow the protocol of their validated technique precisely.

Instrument preparation: The acquaintance test serves as the examiner's opportunity to verify that all sensors are properly placed and functioning. Examiners using outdated or poorly maintained equipment — a concern addressed in our equipment alert guide — should be especially attentive during this phase.

Examinee management: The examiner's demeanor during the stim test is critical. An overly theatrical presentation may seem manipulative, while an understated delivery may fail to achieve the psychological goal of building instrument belief. Professional training emphasizes a confident, matter-of-fact approach. Understanding the role of the examiner during these procedures is essential for producing reliable results.

Documentation: The acquaintance test chart should be retained as part of the examination file, even though it does not contribute to the scoring or diagnostic opinion. It serves as evidence that the required procedure was performed and can be valuable for quality control review.

Countermeasure awareness: Both procedures give the examiner early opportunities to detect potential countermeasure attempts. Unusual breathing patterns, excessive movement, or deliberate physiological manipulation during the acquaintance test can alert the examiner to issues that might compromise the formal test.

For examinees preparing for testing, understanding these procedures in advance can reduce anxiety. Our polygraph pre-test questionnaire guide covers the paperwork and preparation that happens before these tests begin.

Your Experience During These Procedures

If you are preparing for a polygraph examination, here is what you can expect during the stimulation and acquaintance test phases:

You will already be connected to the polygraph sensors before either procedure begins. The examiner will have placed respiration sensors around your chest and abdomen, finger plates or attachments for electrodermal activity, and a blood pressure cuff on your arm. For more on what to expect, see our guide on 5 things to know before a lie detector test.

During the stimulation test, you will typically be asked to choose a number or card, and then deny having chosen it when asked about each option. The examiner will then tell you which number or card you selected, demonstrating that the polygraph detected your deception. This is entirely normal and expected — the purpose is to show you that the instrument works.

During the acquaintance test, you will answer a series of simple questions while the examiner observes the chart data. This is your opportunity to become comfortable with the process — the rhythm of question and answer, the sensation of the sensors, and the feeling of sitting still during chart collection.

Neither procedure counts toward your test result. They are preparatory steps designed to ensure that both you and the instrument are ready for the formal examination that follows. The examiner uses this time to calibrate the equipment and observe your baseline physiological patterns.

If you are concerned about memory and polygraph testing or the differences between single-issue and multi-issue polygraph tests, reviewing these guides beforehand can help you feel more prepared.

Ready to schedule your examination? Book a polygraph test with a qualified examiner today.