If you’ve ever been accused of something you didn’t do, or if you have ever suspected someone of lying to you, you may have wished you had a polygraph test around to find out the truth! We see these tests – commonly called “lie detector tests” – all the time in movies and TV shows. But how do they work? And are polygraphs accurate?

What is a Polygraph?

A polygraph is an instrument used to detect and record human physiological characteristics and changes in such characteristics. Pulse and respiration, heart rate/blood pressure and skin conductivity are all characteristics measured by polygraphs. Polygraphs are commonly used in the United States justice system, but is there substantial scientific evidence to support their usage? First, let’s look into how polygraph examinations work.

 

Some individuals, with practice and mindfulness, can out-smart polygraphs by calming themselves and changing their physiological responses.

 

How a Polygraph Test Works

The first phase of a polygraph examination is the in-person interview that examines biographical data, the individual’s attitude toward dishonesty and his or her beliefs about the test itself. The subject’s responses and behaviors are recorded as interpretable data during this interview.

The second phase of the test is considered the polygraph test proper, which begins with a pre-test, explaining the equipment, and how the test will proceed. Then, the actual polygraph exam begins where the subject is asked a series of questions pertaining to the specific case and requiring a yes or no answer. The subject is connected to the recording systems during the test.

Are Polygraphs Accurate?

The validity of polygraphs has been controversial for quite some time, due to the lack of evidence that specific physiological patterns explain or detect deception. Also, a truthful individual may be nervous or anxious when answering honestly, providing misleading data. Similarly, a dishonest individual may not exhibit any symptoms of anxiety, again providing misleading data.

It is common for subjects to fear that the test is working and then become nervous, even though he or she may be telling the truth. Therefore, the physiological response to becoming anxious or fearful appears as a lie. On the other hand, some individuals, with practice and mindfulness, can out-smart polygraphs by calming themselves and changing their physiological responses. These inconsistent results are what spread controversy over the accuracy of the tests. It is impossible to say with confidence that polygraphs should be relied upon as evidence in legal cases.

So what would be a better option? Recently, neuroscientist researchers have developed a new outlook on lying.

Brain Scans

A study conducted by Temple University in Philadelphia, Pennsylvania found that the brain is working overtime in order to lie. The study took 11 participants, half of which were asked to lie about shooting a gun and the other half asked to tell the truth. Each participant’s brain activity was being monitored by a functional MRI (fMRI) as he or she was also connected to a polygraph.

 

A study conducted by Temple University in Philadelphia, Pennsylvania found that the brain is working overtime in order to lie.

 

The fMRI concluded that the activity in the brain was much greater when the subjects were attempting to lie. The frontal lobe, temporal lobe, and limbic system were all active during the lying process, whereas the subjects who were telling the truth brains hardly showed any activity. Liar, liar, brain’s on fire! {click to tweet}

What’s the Consensus?

So, are polygraphs accurate? Although polygraphs are widely used for government background checks and security clearances, it seems that the use of fMRI’s is onto something big when it comes to finding out the truth. Although more expensive than polygraphs, fMRI’s used in the justice system may be worth the price to put the right culprit behind bars.

For articles similar to this one, check out the studies and posts below:

https://www.sciencedaily.com/releases/2016/11/161103141437.htm

http://www.apa.org/research/action/polygraph.aspx

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