Controlling your physiology to fool a polygraph - Does it work?

This device measures physiological indicators such as blood pressure, pulse, respiratory rate, and skin conductivity while asking a series of questions. Polygraphs are commonly used as lie detectors. The belief is that deceptive answers will produce physiological responses that can be detected by the polygraph. However, the accuracy and reliability of polygraphs have been debated for decades.

Polygraph accuracy

The accuracy of polygraphs has been widely disputed. Reliability varies based on the examiner’s skill and testing procedures. The American Psychological Association estimates the accuracy of polygraph tests at 61-90%. However, the National Research Council states 53% accuracy for single-issue tests like criminal investigations. The variability in polygraph accuracy casts doubt on its validity in judicial proceedings.

With polygraphs having questionable accuracy, some subjects have attempted various countermeasures to beat the tests by controlling their physiology. Some reported strategies include:

Physical countermeasures – Biting the tongue, pressing toes to the floor, or placing tacks in shoes cause mild pain to create physical responses unrelated to the questions. This covers up deceptive responses.
Mental countermeasures – Silently counting backward, doing math problems, or visualizing calm scenes generates alternative mental activities to decrease emotion-based reactions.
Breathing techniques – Slow, regular breathing helps minimize respiration changes when lying. abdominal breathing rather than chest breathing reduces measurable respiration changes.
Muscle tensing – Flexing and contracting arm, leg, or buttocks muscles create artifacts in the blood pressure/pulse measurement unrelated to questions.
Drug use – Some drugs like beta-blockers help reduce detectable changes in blood pressure and heart rate.

However, these approaches have mixed results in fooling polygraphs. Specially trained examiners detect physical movements or irregular breathing and ask more questions to compensate. And countermeasures themselves elicit a stress response.

Does controlling physiology beat the polygraph?

There is limited scientific evidence that physiological countermeasures beat a polygraph conducted by an experienced, capable examiner. In real-world criminal cases, most attempts to artificially manipulate lie detector test results are detected. However, some individuals minimally influence their results by remaining calm and using certain countermeasures. For accurate, reliable results, polygraph examiners should:

Use control questions and establish baseline physiology
Observe behavior and question patterns of response
Repeat or rephrase key questions multiple times
Conduct post-test interviews to review reactions

While countermeasures artificially modify some responses, they cannot completely hide all signs of deception from a thorough examiner. However, the marginal reliability of polygraphs, susceptibility to countermeasures, and psychological manipulation mean polygraph evidence should not be used exclusively to confirm truthfulness or determine guilt. At best, polygraphs contribute supporting information when combined with a full investigation process and strong corroborating evidence.