Can you really prove if someone is lying by hooking them up to a machine and running some
tests?
Apparently so if you use a polygraph, otherwise known as a lie detector.
It works by measuring changes in the body such as blood pressure, pulse, respiration,
and skin conductivity when a person is asked a series of questions.
How reliable is a lie detector and are the results ever wrong?
That’s what we intend to get to the bottom of in this episode of The Infographics Show:
How Can You beat a lie detector?
Before we answer this question let’s first look back at the history of the polygraph
machine.
Understanding when someone is lying was considered important way back in Ancient China and one
of the first established methods was to look for signs of stress because when a person
lies, they become stressed.
One sign of this stress is when a person’s mouth starts to go dry, so to test this the
Chinese would ask the person being questioned to chew a handful of rice during the interrogation.
Once the interview was over, the grains would be spat out and examined.
If the rice was moist they knew the person was likely being truthful and if the rice
was dry, that meant the person was lying.
Jumping forward to the 1900’s, we have Sir James Mackenzie, a Scottish cardiologist and
a pioneer of medical work studying the heart and it’s function in the body.
In his 1902 book, The Study of the Pulse, he described an instrument he had invented
called a polygraph, which allowed the user to correlate a person’s pulse with the beat
of the heart itself.
When a person was hooked up to the machine it would scratch out the pattern of the heart
rate on to paper, via an ink-writing device.
This allowed irregularities in the heart rate to be detected visually.
But it was a rudimentary contraption and it wasn’t until 1921 in Berkeley, California,
when the official polygraph machine for lie detecting was invented.
The machine was presented by a medical student named John Augustus Larson.
He had decided to build a device to assist investigators in criminal cases.
This also led him to being the first person ever to measure more than one body process
at a time.
Ok, so to understand how to beat the detector we need to know exactly how it functions.
When a person takes a polygraph test, they have sensors attached to their body to pick
up different signals.
Some things that are measured include breathing rate, the person's pulse, their blood pressure
and their perspiration, and sometimes a polygraph will also record arm and leg movements.
The questioner starts by asking three or four simple questions to establish what is considered
normal bodily responses when the person responds.
These are the control questions.
Then the real questions being tested by the polygraph are asked and compared.
Throughout questioning, all of the person's signals are recorded on the moving paper.
A polygraph examiner can observe the graphs as the test is happening; to see how the person
is reacting and judge whether or not they are being truthful.
Changes such as heart rate speeding up, blood pressure increasing and a person starting
to sweat more indicates that they are lying.
But is a polygraph test really accurate?
The accuracy of polygraph testing is controversial and can never be 100%.
The American Psychological Association (APA) stated in a 2004 report “there is no evidence
that any pattern of physiological reactions is unique to deception.”
For example an honest person might be nervous when answering truthfully and a dishonest
person may be confident enough to keep their cool.
The APA also reported that there is evidence to suggest that typical polygraph examinations
detect deception better than chance, but with error rates that can result in failing to
detect guilty people.
Ok, so that means the test can be beaten right?
From our research it seems there are a few ways to try and beat the test but it’s not
as simple as imagining happy thoughts while lying and stressful ones while telling the
truth.
So what is the best way to outsmart the lie detector test?
According to Dr. Anne Helmenstine, a Ph.D. in biomedical sciences, the two best ways
to beat the test are one - to get completely into a Zen state of mind or remain totally
stressed out during the test.
Easy right?
If you’re a Buddhist monk, maybe so, but few of us have this much control over our
mood.
One way to trick the test is to identify the questions that are irrelevant - the control
questions.
Examples of irrelevant control questions that have nothing to do with the interrogation
are: “What is your name?”
or “What city do you live in?”
When asked these questions, change your heart rate, respiratory rate, blood pressure and
the amount you sweat.
Then when you answer the relevant questions even if you lie, it will look like a normal
response as compared to the control answers you gave.
But how can you make your body behave this erratically?
Some of the suggestions we found online include thinking scary thoughts when you recognize
a control question.
Or make yourself sweat by trying to workout a tricky math problem in your head like dividing
243 by 7.
Or even bite your tongue to cause yourself pain, as pain produces a similar physiological
response as lying.
We also found an article in British newspaper The Mirror, who interviewed Doug Williams,
a police officer who joined the force in Oklahoma in 1972 and as part of his training actually
went to polygraph school.
As time passed he began to tire of the process of doing test after test and so begin to wonder
exactly how effective the results were.
Williams eventually worked out his own unique way to cheat the system.
He explained to Radio Show, This American Life, "It wasn't until my friend came in and
started talking about the pucker factor and tightening up the anal sphincter muscle when
he was under stress.
And that, as it turned out, proved to be the trick to duping the polygraph machine - clenching
your anus.”
Why did this work, I hear you ask?
It’s because tightening up the anal sphincter muscle and stopping bowel movements creates
a cardio rise.
So though a lie detector can reveal whether a person is telling the truth or not, it looks
like it’s also possible to beat it.
Do you know of other techniques that can be used to fool a lie detector?
If you do, let us know in the comments.
Also, be sure to check out our other video called What Are the Signs That You Are a Psychopath?!
Thanks for watching, and, as always, don’t forget to like, share, and subscribe.
See you next time!”