What You Should Know About Polygraph Tests

Before undergoing a Polygraph test

You need to understand what it is all about. There are three main types of Polygraph tests. They are False positives and Accuracy tests. Let's take a look at these tests to see what you should know. First, you should know that Polygraph questions are yes-or-no. Unlike interviews, the questions asked during a Polygraph test cannot be personal opinions. They must relate to a factual event in the past, with only one interpretation possible. Also, questions about religion, politics, or sexual subject matter are not permitted.

Techniques used to test for deception

One of the techniques used in the polygraph is the "control question." This technique works to compensate for the inherent problems of the recognition test. To detect deception, the subject must exhibit sympathetic arousal and a larger physiological response to the correct choice than the incorrect one. Control questions, on the other hand, provide a stronger competing stimulus for the innocent subject. Polygraph examiners use this technique for criminal investigations.

The polygraph uses a machine to measure three physiological systems. The instrument measures changes in heart rate, blood pressure, and sweat gland activity. This reflects the state of arousal in the person's autonomic nervous system. The autonomic nervous system contains two types of nerves: the parasympathetic nerves which conserve energy, and the sympathetic nerves that prepare the body for a fight-or-flight response. By measuring these changes, the examiner can determine whether the person is deceptive or not.

Modern functional imaging techniques, like fMRI, are also being developed for deception detection. fMRI can detect neural activity associated with emotional and psychological processes, which are relevant to detecting deception. However, there is limited data available on the accuracy of such techniques. These techniques are still in the experimental phase and may be only of limited use. This method is still an excellent choice for deception detection, but it is not a replacement for the polygraph.

Accuracy of the test

The accuracy of a polygraph test depends on the degree of evidence a subject provides to support a particular alternative. A more specific test indicates less deception and more truthfulness. The definitions and quantitative relationships of these terms are shown in Box 2-1. This document is a brief summary of the most important issues in polygraph testing. It outlines a few important criteria used to evaluate the accuracy of a polygraph test.

The accuracy of a polygraph test depends on the question and answers of the examinee, as well as the management of the test. Good tools and questions are necessary to assess test accuracy, but the examiner's experience and training are essential. An examiner who is well-versed in polygraph testing is a key factor in accuracy. However, he cannot prove the innocence or guilt of an individual based on the results of a polygraph test.

The reliability of a polygraph test depends on how well it can identify the truthfulness or lies of an individual. In general, a test is reliable when the results are highly correlated with truthfulness or deception. But some polygraphs can be less reliable than others. Those with TBI or brain injuries, for example, may not be trustworthy. If the examinee is cooperative and communicates well with the examiner, the test is likely to be reliable.

False positives

If a polygraph has 99 percent validity, there would still be ten false positives for every guilty person found. Yet, the percentage of false positives is far greater than that. In some cases, the polygraph might even be overly sensitive, leading to overly high false positive rates. This is especially true when the polygraph is being used for criminal investigations. Here are some ways to minimize polygraph false positives:

First, avoid admitting to relevant questions during the polygraph. The better you can avoid making such admissions, the better. Agencies generally look less favorably on applicants who admit to certain things after the polygraph. That's because the polygrapher is trying to determine whether the individual is lying or not. The same goes for the person's data during the pretest and posttest phases. False positives on polygraphs can be a red flag for a crime.

Moreover, polygraphs are based on faulty assumptions and can be manipulated by a single person. These false positives can cast a negative mark on an applicant's credibility, which undermines the process of fair hiring. Furthermore, in most situations, polygraph false positives are permanent and cannot be appealed. Instead, they can only be dealt with by the law. So what's the solution?