The Polygraph and Lie Detection (2003) / Chapter Skim
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1 Lie Detection and the Polygraph
1 Lie Detection and the Polygraph
Pages 11-28
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From page 11... ...
In the 20th century, lie detection took on scientific aspects with the development of techniques that use measures of physiological responses as indicators of deception. The best known of these is the polygraph.
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From page 12... ...
THE INSTRUMENT, THE TEST, AND THE EXAMINATION Polygraph testing combines interrogation with physiological measurements obtained using the polygraph, or polygraph instrument, a piece of equipment that records physiological phenomena typically, respiration, heart rate, blood pressure, and electrodermal response (electrical
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From page 13... ...
According to some polygraph theories, a deceptive response to a question causes a reaction such as fear of detection or psychological arousalthat changes respiration rate, heart rate, blood pressure, or skin conductance relative to what they were before the question was asked and relative to what they are after comparison questions are asked. A pattern of physiological responses to questions relevant to the issue being investigated that are stronger than those responses to comparison questions indicates that the examinee may be deceptive.
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From page 14... ...
Different polygraph techniques are defined in part by the ways the relevant and comparison questions are selected and placed in a polygraph test. A considerable portion of the empirical research on polygraph testing focuses on validating particular techniques or comparing the performance of one technique with another.
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From page 15... ...
Department of Energy and other federal agencies. As these brief descriptions make clear, polygraph testing techniques vary in the ways the relevant and comparison questions differ and in how these differences, combined with an examinee's physiological responses to them, are used to make inferences about whether the person may be lying in response to the relevant questions.
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From page 16... ...
This process often involves a demonstration in which the examinee is asked to lie about an unimportant matter, and the examiner shows the instrument's ability to detect the lie; these demonstrations sometimes involve deceiving the examinee.4 In comparison question testing, the interview is also used to help the examiner decide which questions to ask for comparison purposes. It is important to note that each of these aspects of the pretest interview may influence an examinee's physiological responses to the relevant or comparison questions and, therefore, the result of the .
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From page 17... ...
In polygraph testing, the use of initial buffer items is intended to reduce situational effects on the examinee's physiological responses. Comparison questions are also used to separate situational effects from the effects of deception by statistical means.
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From page 18... ...
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.
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From page 19... ...
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.
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From page 20... ...
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.
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From page 21... ...
What matters most to investigators and is reported to Congress are the number of examiners who were ultimately "cleared," the number subjected to adverse personnel actions, and the security violations revealed. From a scientific standpoint, however, detecting deception and revealing truth are two distinct purposes of polygraph examinations or any other technique for the psychophysiological detection of deception.
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From page 22... ...
In this case, the polygraph test has a useful role independently of whether it can accurately detect deception: it is effective if the examinee believes it can detect deception. Admissions of this kind provide evidence of the value of the polygraph examination for investigative purposes, but they do not provide evidence that the polygraph test accurately detects deception.
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From page 23... ...
" Some analysts believe that such questions, because they do not refer to specific past events, are more similar to comparison questions than are the relevant questions that can be asked in an event-specific investigation. For this reason, it has been argued that it is inherently more difficult to discriminate deception from truthfulness in a screening context (Murphy, 1993~.
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From page 24... ...
If the answers to such questions are likely to be known only to the investigators and to the organization's members and close associates, the situation is amenable to the use of tests of the concealed information type, which are not otherwise considered to be applicable to screening situations. The ability of polygraph testing to uncover the deceptions of interest and to serve broader law enforcement or national security goals may depend on the purpose of the test and the kinds of acts that are the subject of the relevant questions.
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From page 25... ...
It may help focus an investigation on particular aspects of a case highlighted by an examinee's physiological responses. And, as noted above, polygraph testing may elicit admissions or confessions of undesired activity from people who believe they are better off to admit certain activities voluntarily than to submit to a polygraph test and risk being accused of these or more serious activities, as well as being accused of deception.
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From page 26... ...
Chapter 7 discusses the issues raised by using polygraph evidence for making practical decisions, particularly in security screening processes, including the issue of combining polygraph evidence with other sources of information. Chapter 8 presents the committee's conclusions about the validity of polygraph testing and its recommendations about the use of the polygraph in employee security screening.
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From page 27... ...
Polygraph examination means a process that encompasses all activities that take place between a polygraph examiner and individual during a specific series of interactions, including the pretest interview, the use of the polygraph instrument to collect physiological data from the individual while the polygraph examiner is presenting a series of tests, the test data analysis phase, and the post-test phase. Polygraph test means that portion of the polygraph examination during which the polygraph instrument collects physiological data based upon the individual's responses to test questions from the examiner.
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From page 28... ...
9. It is also possible for polygraph examinations to result in false confessions, just as with other interrogation techniques (Kassin, 1997, 1998~.
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