Are Polygraph Tests the Most Accurate Way to Determine if Someone Is Telling the Truth?

Check out this answer from Consensus:

While polygraph tests can provide some insights into a person’s physiological responses during questioning, they are far from being the most accurate way to determine if someone is telling the truth. The high rate of false positives, methodological flaws, and ethical concerns make polygraph tests a controversial tool in both investigative and legal contexts. More reliable and scientifically validated methods are needed to accurately assess truthfulness and deception.

Polygraph tests, commonly known as lie detector tests, have been a subject of debate for decades. These tests measure physiological responses such as blood pressure, pulse, respiration, and skin conductivity while the subject answers a series of questions. The underlying assumption is that deceptive answers will produce physiological responses that can be differentiated from those associated with non-deceptive answers. This article explores the accuracy of polygraph tests in determining truthfulness and examines the scientific evidence supporting or refuting their reliability.

The Science Behind Polygraph Tests

Polygraphy is based on the theory that lying produces specific emotions, which in turn cause measurable physiological responses. Modern polygraph tests typically involve the control question test and the guilty knowledge test. The control question test compares responses to relevant questions with responses to control questions, while the guilty knowledge test assesses responses to questions about information only the guilty party would know2.

Accuracy and Predictive Power

Several studies have questioned the accuracy and predictive power of polygraph tests. For instance, Brett, Phillips, and Beary analyzed data from field studies of suspected criminals and found that the polygraph detected liars at a rate barely better than chance. They concluded that the polygraph generates a significant number of false positives, incriminating innocent individuals1. Similarly, another study highlighted that the positive predictive value of the polygraph is poor, with most positive results being false positives3.

Admissibility in Legal Systems

The admissibility of polygraph evidence in court varies by jurisdiction. In some countries, polygraph results are used as part of the investigative process but are not admissible in court. For example, the English judicial system has started to use polygraph tests under specific conditions, but their broader admissibility remains limited5. The debate over the reliability and ethical implications of using polygraph tests in legal proceedings continues4.

Case Studies and Practical Applications

Despite the controversies, polygraph tests are still used in various practical applications. For instance, in the United States, postconviction polygraph testing of sex offenders is a common practice, although it has faced criticism on scientific and ethical grounds7. Case studies have shown mixed results, with some instances where polygraph tests have helped uncover the truth, while in others, they have led to false confessions or wrongful accusations6 9.

Criticisms and Limitations

Critics argue that the polygraph lacks a verifiable scientific basis and suffers from various methodological issues, such as examiner bias and sampling problems. The physiological responses measured by the polygraph can be triggered by factors other than deception, such as anxiety or fear, making it difficult to distinguish between truth and lies8. Moreover, the literature supporting the high accuracy claims of polygraph tests is often flawed and lacks empirical rigor10.

Are Polygraph Tests the most accurate way to determine if someone is telling the truth?

Guy Madison has answered Unlikely

An expert from Umeå university in Psychology

It’s a difficult question because it includes a comparison: “the most accurate”. So the question then becomes, compared to what? To find out the thruth from objective sources is probably the best, but if you compare to looking the suspected liar in the eyes, a polygraph, or e-meter, or Galvanic Skin Response meter is probably better.

What such an instrument does is measure autonomic responses of the sympathetic nervous system. The lie detection test, however, also includes procedures carried out by a human operator, which are therefore susceptible to subjectivity. The operator has to ask series of questions that consitiute a mix of benign, neutral topics (e.g. “what did you have for breakfast today”), some are related to the suspected lie, and some are generally contentious (e.g. “have you ever been unfaithful”), and the operator interprets and assesses the readings and compares them across types of questions, chooses new questions based on readings for previous questions, and moves on in an iterative fashion. This process is clearly subjective to a substantial extent.

But another problem is that detecting lying is this fashion makes several assumptions that are not always met, for example that the liar has a typical moral stance, is aware that they are lying, and actually feels embarrassed about it. This kind of test does typically not work for sociopaths and psychopaths.

Are Polygraph Tests the most accurate way to determine if someone is telling the truth?

Claire McAulay has answered Unlikely

An expert from University of Sydney in Psychology, Medicine

My understanding is that they are a measure of autonomic arousal which is not believed to universally be a sign of lying, but rather, might be considered physiological signs of discomfort. So someone lying without feeling uncomfortable about it would not score positively on a polygraph test, whereas someone who is not lying but is nervous about a false positive, is likely to induce that result. Some findings of usefulness nonetheless rely on subjective interpretation by the examiner.

https://theconversation.com/is-a-polygraph-a-reliable-lie-detector-104043

Are Polygraph Tests the most accurate way to determine if someone is telling the truth?

Gavan P McNally has answered Unlikely

An expert from UNSW Sydney in Psychology, Neuroscience

Polygraphs measure autonomic arousal (heart rate, respiration rate, sweaty palms etc). We tend to show autonomic arousal during emotional experiences. The rationale behind the polygraph is that if you lie, then you are likely to experience some arousal whilst lying (eg, due to fear of being caught), which the polygraph can measure. This may be true, but we can all be worried, anxious, or stressed when being questioned leading to many false positives.