My latest issue of the Skeptical Inquirer came today, and there’s an article by Alan P. Zelicoff attacking the validity of polygraph tests. He says that the polygraph is “no more capable of assessing truth telling than were the priests of ancient Rome standing knee-deep in chicken parts,” and that the polygraph’s main purpose is to bully people into confessing by telling them that their response to a certain question indicates deception. They are then asked to “clarify,” causing them to give out more and more information.
Unfortunately, the article is very poor for an SI story. The author states that “dozens of studies over the past twenty years conducted in psychology departments and medical schools all over the world have shown that the polygraph cannot distinguish between truth-telling and lying,” but fails to cite even a single one of those studies. He mentions a handful of anecdotal examples of polygraph failures, but we know that anecdotal evidence is useless.
So, what’s the straight dope? I’ve always heard that polygraphs work at around 90-95% accuracy. Even when they fail, they give “indeterminate” results. Only a rare handful of individuals can lie through their teeth and pass with flying colors. Is this all a giant urban legend?
How can polygraphs remain so popular in law enforcement and rooting out spies if they are total nonsense? Wouldn’t somebody notice that the test indicated deception on questions where the subject was obviously telling the truth (e.g., stating his name) and realize something was fishy?
My friend on the force says that there are ways of making the results inconclusive without necessarilly showing that you are lying.
Before the polygraph is administered, put a tack under your big toe. When they ask a question that you must lie about, applying pressure downward. The pain response will be sensed by the polygraph, and will distort the reading.
Also, if you clench your butthole muscles during said period, it will also distort the results.
The rational behind this is that an inconclusive reading is better than failure as far as the polygraph is concerned.
I think you are asking the wrong question. Where is the proof that they work? After all, no court has been shown enough scientific proof to allow the evidence in court.
The big problem with them as far as I am concerned is that they are so subjective. You have to rely on the person interperating the results. There are no clear standards for how they work etc.
It depends on what you mean by the term “work”. As a black and white “He dunnit” machine, no they don’t do it very well. If they are used to get indicators, they do a pretty fair to good job. What they are very good for though, in connection with obtaining indicators, is the psychological effect on the test subject. With your average hard-case/true criminal, they aren’t good for much more than a formality. For your average street punk types, “one-hit wonders” like company embezzlers, etc… It’s not so much a tool that gives the answers on paper, but a tool that assists an interrogator by observing the reactions of the person that’s strapped in. Lying isn’t that hard. Lying well is only moderately difficult. Lying well when you believe you are connected to a machine that will “light up like a neon sign” when you do lie, is very tough. Quite simply, the person starts trying too hard to be calm, thus making himself nervous, and cracking due to the added pressure of a machine that nobody really cares about all that much.
Polygraphs measure pulse, breathing and perspiration. Nervousness causes certain patterns in breathing, etc, or rather the interuption of the baseline pattern established at the beginning of the test. If lying makes a person nervous, then the polygraph picks that up. If lying doesn’t make a person nervous, then the polygraph will pick up nothing. That leads to the absurd result that people with highly active consciences will fare worse on a polygraph than those without one.
WARNING: Anecdotal Evidence Alert
Each of the following happened to me personally or to a source I trust.
Subject 1 was an American who had deserted from the Rhodesian army, and didn’t want a prospective employer to know that. (Subject believed that service in the Rhodesian army would affect his U.S. citizenship.) He had contracted malaria in Rhodesia.
He was applying for a job in the food service industry and knew that he would be asked health questions during his polygraph. If he told them he had had malaria, that could have led to the questions he did not want to answer. So he lied. When asked if he had ever had a serious illness, he said “no”, and the machine didn’t burp.
Subject 2 was 19. He had, at that time, never smoked marijuana. The ex-cop polygraph operator refused to believe that and badgered him about it before the test. During the test, the nervousness induced by the operator’s suspicions and badgering caused a reaction on that question.
Subject 3 never completed any of the 3 or 4 tests that were attempted to be administered to him. The operators could never get a baseline. That apparently stems from subject 3’s extreme annoyance that anyone would think him capable of lying.
Subject 4 has a criminal record. He passed a polygraph in which he denied having a record by lying on every single question. He had gone equipped with a fake ID and lied about his identity and everything else. I got the story from his wife, who has couldn’t tell a lie if her life depended on it.
Thanks for the responses everyone. It looks as though polygraphs have entered into the realm of ULdom. Everyone “knows” they work, despite the complete lack of evidence.
I’m pretty shocked that the government uses them so frequently when they are so atrocious. Yes, I know the CIA spent $20 million on psychics, but still.
I initiated one of my few topics in GD on this very issue. Though the thread got derailed by The Ryan’s concern over the minutiae of word choice, there are quite a few interesting links provided by JonF and others. In short, I think the general consensus was there is no evidence indicating polygraphs are any better at detecting lies than a human interrogator. And I certainly don’t think they should be used in any circumstance that could affect someone’s life, with the possible exception of using it as a tool in an attempt to elicit a confession in a criminal case.
I spent 5 years doing tech support for a company that sold medical sensors and software. Polygraphs do NOT provide any information that is useful in detecting lies.
If a subjects galvanic skin response and respiration rate increase, a trained eye will indeed spot that change. I also spent plenty of hours hooked up as a demonstration. I never tried a tack in foot, but every thing else works to throw off the data. These machines were incredibly sensitive, if a lamp or extension cord is too close, you get useless data. Further, the sensors only give information on the subject's stress level. This is great if you're helping a client eliminate stress. It useless at detecting liars. As stated, if an individual is accustomed to lying casually, or convinced that the machine won't work, or does not suffer pangs of conscience etc their stress level remains unchanged.
It was however fun to hook up friends, ask some normal preliminary questions and then "Have you ever had sex with a farm animal!". The subject is shocked by the nature of the question. They may feel angry or set up. Stress levels rise. You point at the graph and say "This spike clearly indicates that you should never let the subject care for your pets while you're on vacation." A good laugh is had by all (except the one in the electrodes)
These are acceptable forms of evidence in US courts.
When they first appeared their accuracy was questioned. After a whole slew of tests showed that they were accurate, laws were passed and we entered the “bloody glove” era.
Polygraphs are not an acceptable form of evidence. There are laws that prohibit employers from perfoming them on employees. Yet, your boss is within the law if they randomly ask you to urinate into a cup.
Therefore:
1 Either the results still aren't in on a procedure that is as old as I am. Or
2 Polygraphs are just that, a combined chart of many types of physical data. They have many medical uses, but are no good at detecting lies.
When Wal Mart came to town several years ago they required a polygraph test. I applied and refused to take the test. Not because I had done anything wrong just that I always considered them to be bulling. They gave me a written test,no leads or hookup wires, and the wording pissed me off so much that I told them to kiss my ass and got up and left the room.
I don’t work at Wal Mart,probably never will.
What about people who have nothing to hide and still cause the machine to react? I once took a polygraph and was refused a job on the basis of the results. The operator said the results indicated I had been “deceptive”. I KNOW that I was being truthful on every question, so there has to be something wrong there. From then on I was not impressed if someone “passed” a test becasue they sure aren’t always reliable.