Polygraph analyses: technical and practical background

Abstract

A lie is not the truth, a common definition found in each dictionary or encyclopaedia. Humans use it in different situations and for various reasons, but in the case of forensics, recruitment, and trust in the company or family, it can be curtailed in order to avoid it or to detect it. One of the possible detection tools is the polygraph, whereby lies may be registered and interpreted by means of physiological activities controlled by the autonomic nervous system, such as sweating, trembling, or changes in breathing or in the heart rate. The analyses of the aforementioned parameters are monitored in response to questions, thus, providing information about a possible lie. Questions should be asked according to one of the approved protocols and given procedures and algorithms, which are constantly developed and revised to provide the best possible results.

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“…This signal, rather than the EEG, is used to assess an individual’s neurological status, as electrodermal activity is more susceptible to emotional changes than cardiac activity [ 100 ]. The EDA signal is used simultaneously with blood pressure, heart rate, and respiratory rate in polygraphs as lie detectors, since they are autonomic responses of the nervous system and are difficult to consciously alter [ 101 ]. The electrodermal signal is also used in conjunction with heart rate in video game and virtual reality development [ 102 ] and, similarly to heart rate, electrodermal activity can translate the level of enthusiasm, frustration, boredom, and game enjoyment.…”