Law enforcement and investigations have long used polygraphs, commonly referred to as lie detector tests. Despite complaints about their validity and accuracy, polygraph tests continue to be used by government agencies and private businesses. The polygraph effect is a psychological phenomenon associated with polygraph tests that occur when examinees make incriminating statements or outright confessions when they are threatened with being tested. Some people confess to guilt simply by mentioning a polygraph test.

Polygraph effect phenomenon

Numerous studies have shown that when criminal suspects or investigation targets are told they will undergo an lie detector test locations across USA, a significant portion make incriminating statements or full confessions before the exam. This phenomenon is known as the polygraph effect or polygraph confession effect. In one study summarized in the American Psychological Association’s Polygraph journal, 80% of participating U.S. police agencies reported observations of the polygraph effect. Admissions occurred during the pre-test while attaching the instruments, or even just when signing the release form. A 1997 study found that suspects made confessions or damaging statements in approximately 50% of polygraph exams – and half of those were before the test’s administration. The implied threat of the upcoming polygraph seems to elicit truth-telling to avoid “failing” the test.

Potential explanations for the polygraph effect

Several theories explain why the polygraph effect occurs:

• The guilty knowledge test – The assumption is that the “intimidating” polygraph equipment and atmosphere make suspects fearful their lies will get caught during the exam, prompting last-minute confessions. Offenders perceive the polygraph as capable of revealing information unknowable any other way.
• Coercion and intimidation – Some critics argue the polygraph effect is not due to “guilty knowledge” but rather the coercive context. Being told you are required to take a polygraph or else be considered “uncooperative” amounts to psychological rubber-hose tactics, in this view. Refusing the test is seen as tantamount to admitting guilt.
• Misconceptions about accuracy – Despite evidence polygraphs are inaccurate, the public and criminal suspects often vastly overestimate their capabilities. The mythic infallibility of the machine compels admissions, much like immunity deals do.
• Relief theory – Knowing they are caught, the impending polygraph provides some offenders an opportunity to unburden themselves of guilt, elicit sympathy, or cast their acts in a mitigated light. Confession brings psychological relief.
• Lack of sophistication – Unsophisticated suspects overestimate the accuracy of polygraph tests and underestimate the need to protect their interests. The “mystique” of the technology intimidates them into cooperating and confessing.

Of course, in many cases, the polygraph effect elicits true confessions from the guilty. However, the phenomenon also induces false confessions from the innocent – as documented in numerous wrongful conviction cases.