Biofeedback Polygraph

Bio – Biological, Feedback – Responses, Poly – Many or more than one, Graph – Recordings/writings.

Also known as BFP, biofeedback polygraph is one of the oldest forms of psychophysiological detection of deception (PDD) technique. Continuous measurements of blood volume pulse, electrodermal activity and respiration rates are taken and the responses to various types of questions are compared in order to indicate if the subject is having some sort of fight or flight response.

John Larson, a Canadian born U.S. citizen is accredited with the invention of the polygraph machine (1921) at the mere age of 21 whilst studying at the University of California. He combined the previous work of William Marston on systolic blood pressure with new measurements of pulse rate & respiration rate. His protege Leonarde Keeler later added the measurement of skin conductivity and made the device portable to give us the modern day polygraph machine.

Polygraph testing has had a tumultuous history with arguments regarding it’s effectiveness and acceptability in a court of law. There are numerous scientific studies either advocating or opposing the probability of a polygraph test in different settings. The simple fact of the matter is this, despite differing probability percentages of articles, a polygraph tests yields results far above that of chance. Legal acceptability differs on a country by country and even state by state basis. In South Africa, there are legal precedents that allow any PDD examination into a court of law (particularly the CCMA) on the grounds of corroborating evidence.