A polygraph is more commonly known as a lie detector test. The term “lie detector test” is a misnomer as the device can’t truly detect a lie but rather it detects stress responses. Let’s look a bit more at the history of this device and the controversy.
The History of the Polygraph
In 1921, a Ph.D. in psychology named John Larson began work on what is considered the first polygraph device. He improved on early technologies that measured breathing, pulse and blood pressure and combined them into one device that recorded all of those measurements simultaneously. The design of the device was based on the premise that lying makes a person nervous. That nervousness can cause physiological changes that can be measured or detected. Larson believed that detecting those physiological changes was the key to determining if a person was lying or being deceptive.
A colleague of Larson’s named Leonarde Keeler contributed to the design of the device by adding a way to measure changes in perspiration/sweat. As time went on, Larson became increasingly concerned about the validity of what he and Keeler had created. He was opposed to the term “lie detector” and began to believe that while the device measured the physiological responses to stress, that stress wasn’t definite proof of deception. He feared that innocent people could score false-positives that would provide results of deception, even if they were being honest, simply because they were experiencing stress.
Keeler, Larson’s colleague, did not share these concerns and patented the device. In 1935, results from a polygraph administered by Keeler were used as evidence in a court case. The suspect was convicted, with the jury weighing the polygraph results heavily. Meanwhile, like Larson, lawyers and scientists had deep concerns over the accuracy of the test and whether a result of deception should be used in court as definitive proof.
Polygraphs in the Present
While the technology used to measure physiological responses has improved and examiners have added a number of control questions with the goal of improving accuracy, doubt and controversy remain. Modern polygraphs measure heart rate, breathing rate and perspiration (sweat) changes. Legal experts and scientists remain unconvinced of the validity of the test, with some estimating that as many as 50% of results showing deception could be false-positives.
In 1998, the Supreme Court of the United States weighed in on the polygraph. The court determined that the risk of false-positives was too high and that passing a polygraph is not definitive proof of innocence. Therefore, any use of polygraphs in a proceeding had to be voluntary, approved by both parties and the results could never be considered or presented as conclusive.
Polygraphs are still frequently used–and not just on cheesy daytime TV shows. Polygraphs are used in security checks and in some types of job applications. Additionally, police sometimes use them during interrogations but this use is often frowned upon for the risk of coercing false confessions.
