How the Polygraph Works
The polygraph measures physiological changes caused by the sympathetic nervous system during questioning. There are a minimum of four recording channels/components required on a polygraph instrument.
At least three subsets of fear are involved in a polygraph test:
- Fear of exposure.
- Fear of detection.
- Fear of punishment or consequences.
The polygraph measures physiological changes caused by the sympathetic nervous system during questioning. There are a minimum of four recording channels/components required on a polygraph instrument.
What the Polygraph Instrument Measures
- Respiration patterns recorded by pneumograph components. Thoracic and abdominal patterns are recorded separately, using two pneumograph components.
- Electrodermal activity reflecting relative changes in the conductance or resistance of current in the epidermal tissue.
- Cardiograph tracings record changes in pulse rate, pulse amplitude and relative blood volume.