Polygraph

A polygraph, commonly called a lie detector, is literally a device for graphically displaying multiple physiological measures of human arousal simultaneously (for example, blood pressure, heart rate/pulse, the skin's electrical conductance via varying levels of water being present). As such, it provides a window into a participant's physiology during interrogations. Lies can cause physiological reactions (that is, stress) that can be monitored with or without instrumentation. Though much research on polygraphs focuses on whether they are completely accurate in determining whether individuals are lying or not, the most successful applications are as aids in eliciting verbal admissions from suspects, rather than providing indisputable evidence on their own. Rarely admissible as prosecutorial evidence, polygraphs typically are not required by courts because to do so would force individuals to provide evidence against themselves. Polygraphs are, none the less, often used for security checks and as part of the employment process for high-security clearance positions in government, intelligence, and military organizations.

Lies are a specific form of deception and have the potential to cause physiological reactions [Page 774](that is, stress) in the liar. The more important to the liar it is to deceive the other person, the more heightened reaction the liar may have to telling the lie. With this said, highly performed, practiced, and planned lies may cause less arousal as the individual becomes used to telling them (the individual may even believe a lie after performing it many times), and spontaneous lies would cause the most stress and arousal.

A polygraph test is conducted using Limestone Technologies' Paragon Acquisition System. Modern polygraphs use objective computer algorithms to ascertain whether there is a higher possibility that participants are lying, rather than the more subjective judgment of the administrator alone.

As such, there are many potential reactions to telling a lie and no universal deceptive reaction, so no single unified method of detecting a lie can exist. However, there are three dimensions of a lie that provide potential deception detection: physiological reaction, observable behaviors that indicate a lack of consistency across nonverbal channels, and the verbal statements an individual makes. Single-cue approaches to detecting deception (for example, pupil dilation) have been shown to be less effective, whereas multimodal-cue approaches are not only more effective but also mirror the natural way humans process social information, providing a more synergistic total picture of an individual's behavior exhibition.