Lie detector tests were designed to sniff out liars. While the technique doesn’t measure deception directly, it analyzes the magnitude of fluctuations in certain physiological functions associated with lying.
Polygraphs have proven to be far more reliable than alternative lie detection technologies, such as EyeDetect and the Computer Voice Stress Analyzer (CVSA).
However, no polygraph exam is 100% accurate.
While the American Polygraph Association (APA) assesses that professionally administered single-issue lie detector tests can be up to 95% accurate, reports of false positives and false negatives aren’t unheard of. These incidents often result from how the brain processes information and the polygraph’s generally stressful environment.
Studies have shown that lying exerts a significant cognitive load. Therefore, you’d expect truth-telling to be easier on the brain.
But that’s not always the case.
Read below as we explore why the brain may often treat truth-telling as a threat during polygraph evaluations.
Unpacking Science Behind Lie Detector Tests
Polygraphs rely on the theory that lying can trigger various changes in certain physiological functions. The technique notably measures fluctuations in physiological aspects controlled by the Autonomic Nervous System (ANS), including respiration, perspiration, blood pressure, and skin conductivity.
Now, the autonomic nervous system is split into two primary divisions – the Sympathetic Nervous System (SNS) and the Parasympathetic Nervous System (PNS). The SNS is responsible for the “fight-or-flight” response.
When activated during a lie detector test, the ANS’s sympathetic nervous system triggers certain physiological changes, which the polygraph machine records.
The polygraph equipment comprises several components, each measuring specific physiological functions. Cardiosphygmographs measure cardiovascular functions, pneumographs track respiratory activity, while electrodermal sensors monitor skin conductivity.
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Why Brain May Treat Truth-Telling As a Threat?
Lie detector tests typically assess whether a subject is honest or deceptive.
Suppressing the truth causes changes in the above-mentioned ANS-regulated functions, leading to a Deception Indicated (DI) verdict.
But as hinted, false positives aren’t unheard of. While these cases may result from several factors, how the brain processes truth-telling is one of the primary triggers.
- Navigating the Stressful Polygraph Atmosphere
Lie detector tests are inherently intimidating experiences. As most exams follow an interview-style approach, in-test anxieties aren’t uncommon.
Note that mental anxiety cannot influence the outcome of a lie detector test directly.
However, excessive stress can stimulate the fight-or-flight response and impact the very physiological functions monitored during polygraph exams.
When an examinee’s sympathetic nervous system is activated, the immediate need is to escape the stressful experience.
- Reenacting Traumatic Experiences
Polygraphing trauma victims is one of the most challenging tasks, even for seasoned examiners.
Humans are naturally wired to block traumatic memories. Sometimes, embracing alternative realities provides the best way to evade unpleasant recollections.
For instance, some questioning lines may cause sexual assault victims or gruesome murder witnesses to misrepresent certain facts of the case.
The examinees aren’t intentionally being deceptive here. Rather, they choose to lie to avoid retraumatizing themselves.
When this happens, a polygraph machine will register deception despite the subject being generally truthful during the process.
- Fear of Incrimination
When it comes to polygraph exams, guilty examinees aren’t always the worried lot. The potential consequences of failing a lie detector test may also cause intense anxiety to honest individuals.
We should point out that polygraphs are largely inadmissible in criminal proceedings. Besides, the Employee Polygraph Protection Act (EPPA) restricts most private sector employers from subjecting their employees to mandatory lie detector tests during recruitment or employment.
However, federal agencies are outside EPPA’s scope. The same applies to lie detector tests conducted in other scenarios, such as infidelity investigations.
When an examinee willfully submits to a polygraph test, they agree to abide by the procedure’s findings. The fear of failing the exam may tax the brain and cause it to treat truth-telling as a threat.
Easing Polygraph Anxiety
To quell polygraph anxiety, examiners must prepare examinees adequately ahead of each evaluation. That includes explaining how the procedure works and performing acquaintance testing to acclimatize the subject to the polygraph machine.
Part of the preparation should also entail assessing the potential usage of countermeasures. While common with guilty examinees, some honest individuals may deploy countermeasures in an apparent move to reinforce their truthful responses to in-test questions.
Examiners should remind subjects to respond truthfully and calmly to each lie detector question. Provided they’re 100% honest, they have nothing to fear.
Next, examiners should schedule polygraph tests in neutral, quiet environments. The testing location must be free from common distractions, such as startling sounds and flashing lights.
Besides, polygraph evaluations should ideally incorporate the examiner and examinee.
A legal parent/guardian or an attorney may constitute a third party, particularly while polygraphing minors. However, lie detector tests shouldn’t be administered before an audience, live or otherwise.
Wrap Up
Lying requires more cognitive load. However, the brain may occasionally consider truth-telling as an existential threat during polygraph examination, leading to false positives.
It takes a certified examiner to determine whether the findings genuinely point to deception or are triggered by the fight-or-flight response.
To conduct a credible polygraph test, in-depth preparation is paramount.
Examiners must establish a rapport with the would-be examinees and explain how the procedure works. Adequate preparation minimizes in-test anxiety, enhancing the credibility of the physiological data collected.
As a parting shot, examiners should document accurate physiological baselines during pre-test interviews. Baseline data serves as a benchmark for analyzing the magnitude of responses to the in-test questioning, enabling examiners to infer deception more accurately.
