Neurophysiology

Technological developments allow unprecedented observation of brain activity in a continued quest to distinguish truth from lies. Neural monitoring, also called brain mapping, neural mapping, or brain fingerprinting, represents the latest potentially objective attempt in improving the accuracy of determining the truthfulness or veracity of a person's statements. Although the traditional polygraph and neural graphing approaches share common elements, neurophysiological approaches present distinct legal and ethical concerns about how this information might be used in legal courts, law enforcement, and national security.

Historically, observation of individuals' behaviors was the most immediate method of determining their statement veracity. Research on deception detection established connections between several different channels of nonverbal behavior (e.g., touch, hand/foot gestures, facial expressions, eye behavior, scent, posture, use of space, and vocal variation) and different types of deceptive behavior (e.g., highly practiced lies, planned lies, and spontaneous lies). With so many channels to simultaneously attend to, deceivers would often “leak” behaviors associated with the truth, mixed in with controlled behaviors associated with their lie, creating a disparity across the behavioral channels. A weak point within this research was the accuracy levels of humans trying to solely use this information to detect deception.

Deceptive behaviors are frequently associated with physiological changes when anxiety about detection is present. Polygraph administration is designed to heighten this anxiety in participants in order to provide clear responses to questions. A traditional polygraph simultaneously measured participants' blood pressure, galvanic skin response, pulse, and respiration as indicators of anxiety-induced autonomic arousal. Inherent within this line of deception detection is the erroneous assumption of a universal arousal baseline across all humans. Not all individuals are aroused by telling lies, and even those who would normally be stimulated by this activity may experience lower arousal levels via practice or planning of the lie (i.e., the stimulating effect of any behavior reduces through habituation across practice/performance of the behavior).

Additionally, counter-polygraph training hampers the polygraph's abilities to detect changes in a person's anxiety or arousal by changing their autonomic reactivity, and although steps have been taken to inoculate many of these hampering methods from affecting a polygraph administration, the reliance on external behaviors and internal aspects of an individual's arousal continue to offer weaker evidence. Consequently, courts continue to view polygraph results with suspicion. The most valuable use of polygraph technologies lies in their ability to elicit subject's verbal statements that could subsequently be used in court, even though the actual polygraph test results could not.