The sensors usually record:. When the polygraph test starts, the questioner asks three or four simple questions to establish the norms for the person's signals. Then the real questions being tested by the polygraph are asked. Throughout questioning, all of the person's signals are recorded on the moving paper.
Both during and after the test, a polygraph examiner can look at the graphs and can see whether the vital signs changed significantly on any of the questions. In general, a significant change such as a faster heart rate, higher blood pressure, increased perspiration indicates that the person is lying.
When a well-trained examiner uses a polygraph, he or she can detect lying with high accuracy. However, because the examiner's interpretation is subjective and because different people react differently to lying, a polygraph test is not perfect and can be fooled. By comparison, your answers to the relevant questions whether they are truths or falsehoods will seem true.
As seen in the film "Ocean's Eleven", one method of ramping up your vital signs when answering control questions is to press down on a thumbtack, or some other sharp object, in your shoe. The pain from doing this will cause most of your vitals to spike, and your response will probably be read as a lie.
So you'll need a back-up plan. The authors suggest thinking exciting or scary thoughts when you recognize a control question. Alternatively, you can make yourself sweat by trying to do a somewhat difficult math problem in your head like dividing by 4.
Similar to the tack-in-the-shoe trick, you could also bite down on your tongue: Pain induces a similar physiological response as lying. In many applications, examiners take a stronger response than to comparison questions as an indication not necessarily of deception, but of the need for further interviewing or testing to determine whether deception is occurring. The lack of such a differential response or a stronger response to comparison questions generally leads to a conclusion that a respondent is being truthful.
A polygraph test is part of a polygraph examination , which includes other components. A critical one, particularly in comparison question tests, is the pretest interview. This interview typically has multiple purposes. It explains the test procedure to the examinee. It explains the questions to be asked so that examiners and examinees understand the questions in the same way. It may be used to convince the examinee that the polygraph instrument will detect any deception.
These impressions, as well as any expectations the examiner may have formed in advance of the examination, are likely to affect the conduct and interpretation of the examination and might, therefore, influence the outcome and the validity of the polygraph examination.
A polygraph test and its result are a joint product of an interview or interrogation technique and a psychophysiological measurement or testing technique. It is misleading to characterize the examination as purely a physiological measurement technique.
It provides instruction on the kind of atmosphere that is to be created in the pretest interview, advises on techniques for convincing examinees of the accuracy of the test, and offers guidance in different ways for different test formats for selecting comparison questions.
Examiners are advised to control these. Polygraph examination procedures often explicitly combine and interweave testing and interviewing. When a polygraph chart indicates something other than an ordinary nondeceptive response to a relevant question, the examiner typically pursues this response with questioning during the course of the examination.
The interview may reveal a misunderstanding of the question, which is then explained and reasked in a subsequent charting. Some examiners believe that an important use of polygraph testing is in helping narrow the range of issues that need to be investigated, using both polygraph and other investigative tools. The important role of interview conditions is also recognized in much of the practice and lore of polygraph testing.
When interviewers are hostile or aggressive, examinees may be less relaxed and may produce different physiological responses than those they would produce in response to calm, friendly questioning. These situational effects represent a challenge to the validity of any physiological test that does not adequately reduce the influence of variations in the interview situation on the physiological responses being measured or separate the effects of the situation from the effects of the condition such as deception that the test is intended to measure.
Comparison questions are also used to separate situational effects from the effects of deception by statistical means. Whether these procedures in fact have the desired effects is an empirical question, which is explored in this book. In order to frame a scientific discussion about the polygraph, we consider the role of this method of detecting deception in American culture and compare it with methods of detecting deception that have been accepted in other cultures. The polygraph, perhaps more than any other apparently humane interrogation technique, arouses strong emotions.
There is a mystique surrounding the polygraph that may account for much of its usefulness: that is, a culturally shared belief that the polygraph device is nearly infallible. Practitioners believe that criminals sometimes prefer to admit their crimes and that potential spies sometimes avoid certain job positions rather than face a polygraph examination, which they expect will reveal the truth about them.
The mystique shows in other ways, too. In popular culture and media, the polygraph device is often represented as a magic mind-reading machine.
These facts reflect the widespread mystique or belief that the polygraph test is a highly valid technique for detecting deception—despite the continuing lack of consensus in the scientific community about the validity of polygraph testing. Ritualized lie detection techniques in many groups, societies, and cultures through the ages share several characteristics that help create a mystique that enables the techniques to be effective. Lie detection rituals involve a socially certified administrator an examiner or interrogator and some device or procedure that purportedly can objectively and publicly identify lying on the part of the examinee.
The administrator—in some cultures, a priest or shaman—has completed a secret or semi-secret training process. The keeping of the secrets of the ritual within a small, select group adds to the mystique e. The examinee, as a member of the society or culture, generally accepts the importance of the lie detection ritual and believes that it is very accurate. Hence, if he or she is telling the truth, there is little or no reason to fear the examination, but if he or she is lying, there is reason to fear it.
Many procedures and techniques have been used in lie detection rituals, including ones that in our society would. Despite the lack of scientific evidence supporting the validity of such techniques, they apparently are useful, as judged by their ability to elicit confessions of truths that are not forthcoming when other methods are used.
Some or all of this usefulness is attributed to mystique—the systems of beliefs that surround and support the techniques. The polygraph testing procedures currently used in the criminal justice system and in several government agencies in the United States and other countries fit this prototype ritual.
A polygraph examiner subculture exists, complete with its own institutions e. Examiners are trained and certified expert by various training institutes, including some private ones and, importantly, by the U.
Department of Defense Polygraph Institute. Members of the polygraph examiner culture have a particular jargon and shared lore that are generally unknown to others. The polygraph device or instrument is purported to have the power to discriminate lies from truths in the hands of a certified and experienced examiner. The polygraph examination follows standardized, ritual-like procedures and usually occurs in a setting designed to evoke associations with science, medicine, or law enforcement, institutions whose certified practitioners are believed to have special powers to uncover truths.
Claims that polygraph testing is a scientific method, together with the establishment of research programs to improve polygraph testing, are useful for building credibility in a society that confers credibility on scientific activities.
Moreover, potential examinees are assumed to believe in the validity of polygraph testing, and its validity is supported by popular culture. These similarities between current polygraph detection of deception procedures and the lie detection rituals of other and former cultures say nothing directly about the validity or invalidity of the polygraph testing for distinguishing truth from deception. They do, however, suggest that some of the value or utility of the polygraph for eliciting admissions and confessions undoubtedly comes from attributes other than the validity of the testing itself.
Polygraph testing may work, in part, because it capitalizes on the mystique that is common to lie-detection rituals in many societies. Any investigation into the scientific validity of polygraph detection of deception must try to identify and distinguish between two kinds of scientific evidence: evidence bearing on the effects of the polygraph ritual and mystique and evidence bearing on the validity of polygraph testing and the polygraph device for detecting deception.
One of these is the difficulty of gaining access to information. Some information of interest to this study, such as the polygraph test records of known spies, is classified for national security reasons. Other information, such as the precise ways particular pieces of polygraph equipment measure physiological responses, is guarded by equipment manufacturers as trade secrets.
Some manufacturers ignored our requests for such information, even though we offered to sign legally binding promises of nondisclosure. Information about computer scoring algorithms for polygraph tests was similarly withheld by some algorithm developers.
All of this behavior makes scientific analysis difficult. Another aspect of the polygraph mystique that creates difficulties for scientific analysis is the strong, apparently unshakeable, beliefs of many practitioners in its efficacy on the basis of their experiences.
We have heard numerous anecdotes about admissions of serious crimes and security violations that have been elicited in polygraph examinations even after background checks and ordinary interviews had yielded nothing. Many of these admissions have been later corroborated by other convincing evidence, indicating that the polygraph examination sometimes reveals truths that might otherwise have remained concealed indefinitely.
We do not doubt the veracity of these anecdotes. However, they do not constitute evidence that the polygraph instrument conveys information that, in the context of the polygraph test, accurately identifies the locus of deception.
Rather, they signify that something in the polygraph examination can have this result. From a scientific standpoint, these anecdotes are compelling indications that there is a phenomenon in need of explanation; they do not, however, demonstrate that the polygraph test is a valid indicator of deception.
From a practical standpoint, it can make a considerable difference whether decisions that rely on polygraph evidence are resting on a scientifically proven device and procedures that is, on the test , on the judgments of examiners, or on the expectation that guilty examinees will be sufficiently fearful of detection to confess. Polygraph examiners and the decision makers who use their reports do not always make such distinctions. That's just not so," Horvath said. You could buy a polygraph [instrument] tomorrow and come to Michigan and you wouldn't be able to practice here because we have a rigorous licensing law, but you could move down to Ohio and open a business tomorrow.
Today, some polygraph examiners take classes and work an internship in order to become an accredited examiner with national associations. Some states also require examiners to be trained. There are many schools around the United States that have been set up to train people to conduct polygraph exams. One of these schools is the Axciton International Academy , which was started by Lee.
Here are the steps that students at the Axciton Academy must complete before becoming licensed forensic pyschophysiologists:. Following the completion of these requirements, the student becomes a polygrapher and may obtain a license in his or her state if that state requires one.
There is no standardized test that all polygraph examiners must pass in order to practice. You are sitting there with wires and tubes attached to and wrapped around your body. Even if you have nothing to hide, you could be afraid that the metal-box instrument sitting next to you will say otherwise.
Fittingly, undergoing the uncomfortable experience of a polygraph test is often referred to as "going on the box. A polygraph exam is a long process that can be divided up into several stages. Here's how a typical exam might work:. There are times when a polygraph examiner misinterprets a person's reaction to a particular question. The human factor of a polygraph exam and the subjective nature of the test are two reasons why polygraph exam results are seldom admissible in court.
Here are the two ways that a response can be misinterpreted:. Critics of polygraph exams say that even more false-positive errors occur in real-world scenarios, which biases the system against the truthful person. These errors are likely to occur if the examiner has not prepared the examinee properly or if the examiner misreads the data following an exam.
The idea of countermeasures is to cause or curtail a certain reaction that will skew the test's result. A subject may attempt to have the same reaction to every question so that the examiner cannot pick out the deceptive responses.
For example, some people will place a tack in their shoe and press their foot down on the tack after each question is asked. The idea is that the physiological response to the tack may overpower the physiological response to the question, causing the response to each question to seem identical.
Whether you pass or fail a polygraph exam will often have very little legal ramification. Often, defense lawyers brag that their client has passed a polygraph. Of course, you will rarely hear of a defendant taking a polygraph if he or she failed it. Polygraphs are rarely admissible in court. New Mexico is the only state in the United States that allows for open admissibility of polygraph exam results.
Every other state requires some type of stipulation to be met prior to admitting polygraph exams into record. In most cases, both sides of a legal case have to agree prior to the trial that they will allow polygraphs to be admitted. On the federal level, the admissibility criteria are much more vague and admission typically depends on the approval of the judge.
The main argument over the admissibility of polygraph tests is based on their accuracy, or inaccuracy, depending on how you want to view it. The level of accuracy of a lie detector depends on whom you talk to about it, Horvath said.
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