Effectiveness of a Lie Detector Test
Commonly referred to as a lie detector, the polygraph machine is used by many public agencies. Although it is most commonly associated with use by the police and other government agencies, it also has a history of use for employment screening. Couples may also use it to find out if a spouse is lying or cheating in the relationship.
Other People Are Reading
-
History
-
John Augustus Larson invented the first machine considered to be a lie detector in 1921, based on an earlier model created by Dr. William Marston. These first polygraphs measured changes in pulse rate, blood pressure and respiration but were not considered overly effective. Leonarde Keeler went on to enhance the polygraph machine in 1939 with what is now considered the prototype of the modern machine, according to Galianos Polygraphe Expert.
Function
-
Modern polygraph machines work by recording physiological variables, including pulse rate, blood pressure and electrodermal activity, among others, according to polygraph expert Andriy Volyk. Polygraph machines record these variables on the examinee while they are asked questions related to the specific issue they are being interrogated for. The polygraph examiner then analyzes the results.
-
Accuracy
-
Scientific circles often regard polygraph tests as unreliable, states Deborah Halber, a correspondent at the Massachusetts Institute of Technology's News Office. Due to variability over which questions are asked, how they are asked and the examiner asking them, the test-retest reliability is threatened, according to the Board on Behavioral, Cognitive and Sensory Sciences and Education (BCSSE). Research by the BCSSE found that reliability depends on the reason for giving the polygraph tests. Percentage accuracies are unreliable when it comes to polygraphs due to the variable data that can be included to calculate the results.
Considerations
-
Although polygraphs are called lie detectors, they do not actually distinguish lies. Polygraphs measure what the polygraph industry considers involuntary reactions from the autonomic nervous system. However, research done by Jennifer Moore of the University of Cincinnati shows that these involuntary reflexes can be manipulated. Countermeasures such as tightening the sphincter muscle and ingesting sedatives can be used to manipulate a polygraph test.
Eliciting Confessions
-
Polygraph examiners can gain a lot of their information before and after the examinee has completed the test. Examiners may encourage the subject to confess before finding out the results by offering a lesser punishment or to help them pass the test, states the BCSSE. While this may increase the overall effectiveness of polygraph use, it does not increase the validity of the test itself.
-
