Lie detection is the practice of determining whether someone is practicing deception. Activities of the body not easily controlled by the conscious mind are compared under different circumstances. Usually this involves asking the subject control questions where the answers are known to the examiner and comparing them to questions where the answers are not known.

Lie detection commonly involves the polygraph but voice stress analysis may be more common because it can be applied covertly and to voice recordings. Polygraph results are sometimes recorded on a chart recorder A polygraph (commonly and inaccurately referred to as a lie detector) is a device which measures and records several physiological variables such as blood pressure, heart rate, respiration and skin conductivity while a series of questions are being asked, in an... Voice stress analysis (VSA) is a controversial technology that attempts to examine and measure a physiological stress component, by extracting micro tremors from the voice of a person and measuring their amplitude. ...

The polygraph detects changes in body functions not easily controlled by the conscious mind such as skin conductivity. Polygraph results are sometimes recorded on a chart recorder A polygraph (commonly and inaccurately referred to as a lie detector) is a device which measures and records several physiological variables such as blood pressure, heart rate, respiration and skin conductivity while a series of questions are being asked, in an...

An FMRI can be used to compare brain activity differences. Functional Magnetic Resonance Imaging (or fMRI) describes the use of MRI to measure hemodynamic signals related to neural activity in the brain or spinal cord of humans or other animals. ...

Electroencephalography is used to detect changes in brain waves. Electroencephalography is the neurophysiologic measurement of the electrical activity of the brain by recording from electrodes placed on the scalp or, in special cases, subdurally or in the cerebral cortex. ...

Another system measures the reflection of infrared light shone through the forehead of a subject.

Brain fingerprinting uses electroencephalography to determine if an image is familiar to the subject. This could detect deception indirectly but is not a technique for lie detecting. Brain Fingerprinting is a technique that measures recognition of familiar stimuli by measuring electrical brain wave responses to words, phrases, or pictures that are presented on a computer screen. ... Electroencephalography is the neurophysiologic measurement of the electrical activity of the brain by recording from electrodes placed on the scalp or, in special cases, subdurally or in the cerebral cortex. ...