Polygraphs are designed to detect deception based on physiological responses.
A polygraph test, commonly referred to as a lie detector test, collects information on physiological responses to a specific set of questions. By assessing changes in respiratory, cardiovascular and sweat glad activity, trained examiners can determine whether a verbal response to a question is truthful. Medical conditions that affect any of the systems being monitored can render test results inconclusive because the physiological response may be a symptom of the affected system.
Mental Illness
Many mental illnesses include symptoms that may affect an accurate reading during a polygraph test. These symptoms include anxiety, rapid heart rate, sweating and physical pain. Because a polygraph measures physiological responses that may include these same symptoms, it may be difficult to determine if the reading is due to the mental illness or in response to the question. Additionally, medications used to treat these symptoms may also alter physiological responses, further complicating accurate interpretation of test results.
Cardiovascular Disease
People afflicted with cardiovascular disease are especially vulnerable to stress on a physiological and psychological level. Polygraphs are designed to interpret similar signs of stress as a way to determine truthfulness. As a coping mechanism to protect the heart, people with cardiovascular disease may experience flight-or-fight symptoms such as rapid heart rate, excessive sweating, labored breathing, gastric or chest pain, and increased adrenaline production that causes muscle tension. These symptoms may mirror an attempt at deception.
Muscle Disorders
Muscle disorders such as muscular dystrophy, myopathy and lupus can cause muscles to become weak or atrophied, thereby sending false signals of inactivity to a polygraph. Other ailments, such as Tourette syndrome, cause uncontrolled muscle movements that can also be misinterpreted by a polygraph. Muscle diseases such as lupus can cause similar physiological symptoms as stress, which include sweating, rapid heart rate and labored breathing, possibly resulting in a false positive for deception.
Pregnancy
Taking a polygraph test can naturally cause stress in anyone. In women who are pregnant, especially those experiencing a high-risk pregnancy, outside stress can cause a fetus to be more active than in non-stress situations. This activity can alter the physiological responses of the mother, causing increased respiratory function, rapid heart beat and uncontrolled muscle activity, resulting in false positive or inconclusive readings.
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