Polygraphs were initially used to detect lying in the early 20th century and have been contentious ever since. Despite its widespread use by law enforcement and government agencies, critics claim it is pseudoscience and easily abused.
During the polygraph test, physiological responses are measured, including blood pressure, pulse, respiration, and skin conductivity. Proponents argue that lying causes subtle bodily changes that are detected. However, claim polygraphers make subjective interpretations that are biased and unscientific. Polygraph exams often begin with a pre-test interview where the examiner gets to know the subject. Next comes the “stim” test which establishes baseline measurements of the subject’s vitals when answering basic questions truthfully. Then comes the main event – the examiner asks several questions, mixing relevant and baseline inquiries. Deviations from the baseline may be indicators of lying.
Common polygraph techniques
- The Concealed Information Test (CIT) tries to uncover knowledge of crime details known only to the perpetrator. One of the items the examiner asks about is the critical detail. The real perpetrator will react strongly to the relevant item.
- The Guilty Knowledge Test (GKT) seeks to determine whether the subject has guilty knowledge about the crime. Questions focus on details of the crime that an innocent person wouldn’t know.
- The Comparison Question Test (CQT) asks probative questions relating to the investigation along with broader control questions about moral acts. Deception is inferred when reactions to relevant questions are greater than controls.
Why polygraph results are questionable?
Critics cite many reasons why polygraphs are questionable:
- Nervous, truthful people fail. The simple act of being questioned produce “deceptive” reactions.
- Sociopaths who don’t feel guilt or anxiety pass.
- Subjects taught countermeasures to alter reactions.
- Polygraph examiners must make subjective interpretations – their biases influence outcomes.
- Peer-reviewed research indicates accuracy rates are not much greater than chance, despite polygraphers’ claims.
Beating the polygraph – Tips from the critics
Polygraph-beating websites have emerged over the years, though most disclaim that they encourage illegal activity.
- Stay calm. Focus on breathing slowly and deeply to keep heart rate and blood pressure stable.
- Briefly flex or bite your tongue during baseline or control questions. It artificially create reactions to mimic deception.
- Learn to identify control and relevant questions. Give yourself a mental pep talk or silently count during relevant questions to diminish emotional reactions.
- Avoid taking countermeasures during pre-test and post-test periods – save them for the main event.
- Prep for the test by sleeping well. Fatigue and anxiety skew results.
- Be well hydrated and avoid caffeine. Dry mouth or excessive sweating affect readings.
- Answer questions firmly, briefly, and without hesitation. Don’t elaborate.
- Request that questions be rephrased if confusing. Don’t speculate – answer only what is asked.
While polygraphs remain controversial, proponents argue they useful if results are assessed cautiously by a skilled examiner. But critics contend lie detector test is thinly veiled pseudoscience that should not be relied upon. The National Academy of Sciences has called for restrictions on polygraph screening programs. Nonetheless, the intrigue surrounding lie detection ensures interest in polygraphs is unlikely to die down anytime soon.