CHRIS McCANDLESS
Portland, OR

Sign up for our newsletter!

General

Lenses and Lies

By on July 24, 2017

The polygraph is an instrument that gets associated with lies. It sends bodily signals from sensors attached to a person subjected to questioning. The reason behind how a polygraph detects lies is that a person is assumed to exhibit changes in the form of emotional arousal and cognitive distress due to stressful exposure of the subject to questioning.

The polygraph relies on its parts to perform lie detection. These parts are wrapped around certain parts of the body to monitor respiration or blood pressure. The other parts of the instrument are attached to the fingers to monitor pulse and sweat patterns. When a person is exposed to questioning about certain issues related to a person’s actions, physiological reactions occur. This serves as the basis to confirm truth or detect deception.

Polygraph Invention

John Larson is credited for having invented the polygraph in 1921. He was a medical student at the University of California at Berkeley and a Berkeley police officer. The instrument was originally intended for police officers to be models as law abiders but had been used extensively in criminal investigations. But it was not until 1936 when the instrument was used in a criminal case for the first time. His pioneer version was able to detect changes in pulse and respiratory rate and blood pressure.

lie detector test

Improvements made to the instrument were initiated by Leonarde Keeler, who had a firsthand experience working with Larson in using the polygraph in criminal investigations, which marked the beginning of polygraph known to us today. He added the third component, which was capable of determining changes in the examinee’s skin resistance. The addition of a series of questions as part of conducting the test came years after. The chart analysis was introduced only in 1958.

Polygraph Use in the US

In the US, the use of polygraph is limited to government and law enforcement. It is also conducted by some private companies but the Employee Polygraph Protection Act (EPPA) of 1988 regulates its use. Some lie detection services are also offered. The services through the use of lie detector test include pre- employment screening, infidelity tests, internal company investigations and false claim examinations.

Polygraph Accuracy

Polygraphs have the accuracy of about 90 per cent, according to the proponents. For its critics, the accuracy level drops to about 70%. The accuracy of polygraph primarily depends on the skill of the examiner, the examinee’s physiology, and the conditions under which it is used. Without extraneous variables that would affect these conditions, results can be close to 100 per cent accurate. However, when conditions are not prime, the accuracy is just like guessing in a true or false test.

Tip Off with Polygraph

A 2012 study revealed that lying particularly effects subtle changes with the way how the human eye behaves. These almost unobservable changes in the behavior of the human eyes when lying are subconscious in nature and cannot be concealed by the examinee in most circumstances. An accuracy of 85% was registered by the eyes as a tool to detect deception. But would this overthrow the polygraph as the most scientific approach to determine lies?

TAGS
RELATED POSTS