A polygraph, commonly known as a lie detector, measures physiological responses in an individual when asked a series of questions. The underlying assumption is that lying may cause changes in certain physiological indicators, which can be recorded and analyzed. However, it's important to note that polygraph results are not foolproof and can be influenced by various factors, including the individual's emotional state and physiological reactivity.
During a polygraph examination, several physiological parameters are typically measured, including:
Heart Rate (Cardiovascular Activity): The polygraph records the heart rate through a cardio cuff or similar device. An increase in heart rate when answering specific questions might be interpreted as a sign of stress or anxiety, which could indicate deception.
Blood Pressure (Cardiovascular Activity): Changes in blood pressure can also be recorded during the examination. Like heart rate, an increase in blood pressure may be associated with heightened stress or nervousness.
Respiration Rate (Respiratory Activity): The polygraph monitors respiration to detect changes in breathing patterns, such as shallower or irregular breathing, which might be linked to deception.
Galvanic Skin Response (GSR): GSR measures the skin's electrical conductance, which can change with changes in sweat gland activity. Sweating is often associated with stress or anxiety, which can be triggered by lying.
It's essential to understand that the polygraph's accuracy and reliability have been a subject of significant debate among scientists and experts. While proponents argue that it can detect deception to some extent, critics point out that the results can be influenced by various factors, such as the examinee's emotional state, fear of the test itself, or the examiner's interpretation.
As a result, the use of polygraph results as evidence varies by jurisdiction, and in many legal systems, it is not admissible as primary evidence in court due to its controversial nature and potential unreliability. Instead, it is often used as an investigative tool or to guide further questioning in some contexts.