The Polygraph and Lie Detection (2003) / Chapter Skim
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3 The Scientific Basis for Polygraph Testing
3 The Scientific Basis for Polygraph Testing
Pages 65-105
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From page 65... ...
We begin by discussing the importance of establishing a solid scientific basis, including empirically supported theory, for detection of deception by polygraph testing. We then present the main arguments that have been used to provide theoretical support for polygraph testing and evaluate them in relation to current understanding of human psychological and physiological responses.
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From page 66... ...
A well supported theory of the test is also essential to provide confidence that the test will work well in the face of efforts examiners may make to produce a false negative result. Spies and terrorists may be strongly motivated to learn countermeasures to polygraph tests and may develop potential countermeasures that have not been studied.
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From page 67... ...
For polygraph lie detection, scientific validity rests on the strength of evidence supporting all the inferential links between deception and the test results. Inferences from polygraph tests presume that deception on relevant questions uniquely causes certain psychological states different from those caused by comparison questions, that those states are tied to certain physiological concomitants, that those physiological responses are the ones measured by the polygraph instrument, that polygraph scoring systems reflect the deception-relevant aspects of the physiological responses, and that the interpretation of the polygraph scores is appropriate for making the discrimination between deception and truthfulness.
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From page 68... ...
For example, might a test result have been different if a different examiner had given the test? · How might the wording or presentation of the relevant or comparison questions affect an examinee's differential physiological responses?
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From page 69... ...
In such ways, a solid scientific base is important for developing confidence in any technique for the psychophysiological detection of deception and critical for any technique that may be used for security screening. THEORIES OF POLYGRAPH TESTING Polygraph specialists have engaged in extensive debate about theories of polygraph questioning and responding in the context of a controversy about the validity of comparison question versus concealed information test formats.
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From page 70... ...
Because of individual differences, the absolute magnitude of an individual's physiological response to a relevant question cannot be a valid indicator of the truthfulness of a response. According to contemporary theories of polygraph questioning, individuals who are being deceptive or truthful in responding to relevant questions show different patterns of physiological response when their reactions to relevant and comparison questions are compared.
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From page 71... ...
Psychophysiological Responses Polygraph testing is based on the presumptions that deception and truthfulness reliably elicit different psychological states across examiners and that physiological reactions differ reliably across examiners as a function of those psychological states. Comparison questions are designed to produce known truthful or deceptive responses and therefore to produce physiological responses that can be compared with responses to relevant questions to detect deception or truthfulness.
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From page 72... ...
The comparison question test and related formats are presumed to establish a context such that an examinee who is innocent of the acts identified in the relevant questions will be at least as concerned and reactive, if not more so, in relation to lying on the comparison questions as about giving truthful answers to the relevant questions. In contrast, the examinee guilty of some forbidden acts is assumed to be more fearful, anxious, or stressed about being detected for lying and, therefore, more reactive to the relevant questions than the comparison questions.
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From page 73... ...
For example, questions related to traumatic experiences may produce large conditioned physiological responses even if the examinee responds truthfully consider the psychological state of a victim or an innocent witness asked to recall specifics of a violent crimewhile a lie about a trivial matter may elicit a much smaller response. Also according to this theory, relevant questions might also produce large responses in innocent examiners who have in the past experienced unfounded accusations that were associated with upsetting or punitive consequences that elevated autonomic activity.
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From page 74... ...
Because the consequences of lying to the comparison questions are thought to be less than lying to the relevant questions, the theory is that lying to relevant questions will be associated with larger physiological responses than lying to control questions. These theories suggest that the detection of deception will be more robust in real-life situations involving strong emotions and punishment than in innocuous interrogations or laboratory simulations.
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From page 75... ...
They thus suggest that comparison question polygraph testing has a significant potential to lead to inferences of deception when none has occurred: that is, they suggest that the polygraph test may not be specific to deception because other psychological states that can result from stimuli arising during the test mimic the physiological signs of deception. The possibility that truthful examiners will occasionally exhibit stronger physiological responses to relevant than control questions based on chance alone also increases the possibility of false alarms.
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From page 76... ...
assume that it is the deceptive response that causes the reactions recorded by the polygraph. Polygraph tests that use the comparison question technique are also
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From page 77... ...
First, the practice of previewing questions with examiners is problematic under orienting theory. Exposure to the relevant questions prior to the examination would tend to decrease the differential orienting response to the relevant and comparison questions and weaken the test's ability to discriminate.
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From page 78... ...
Interpretation of a polygraph test has typically been based on the relative size of the physiological responses elicited by relevant questions and the associated comparison questions (e.g., Podlesny and Raskin, 1977; Lykken, 1998~. If the assumptions about large and involuntary responses to relevant questions are true, the polygraph test would be characterized by high sensitivity and specificity it would discriminate very accurately between deception and truthfulness and it would be immune to countermeasures.
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From page 79... ...
This source of inconsistency and potential unreliability in test administration was a stimulus for developing comparison question testing techniques that standardize the relevant and comparison questions across examinations and examiners. For example, directed-lie comparison question test formats have been advocated as superior to probable-lie variants because in the latter format, "it is difficult to standardize the wording and discussion of the questions" (Raskin and Honts, 2002:22~.
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From page 80... ...
Screening uses of polygraph testing raise particular theoretical issues because when the examiner does not have a specific event to ask about, the relevant questions must be generic. If a comparison question testing format can meet the challenge of calibrating questions to elicit the desired level of response in a specific-incident test, it does not follow that the same format will meet the challenge in a screening application because the relevant questions do not refer to a specific event.
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From page 81... ...
To the extent that these principles do not hold universally, an examiner's rapport with the examiner, the desired understanding of the polygraph examination and questions, and the clinical skill in determining the person's veracity (i.e., detection of deception from demeanor) are all important in distinguishing among individuals who have physiological responses not indicative of deception (e.g., anxiety or anger regarding relevant questions, insufficient emotionality about the comparison questions)
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From page 82... ...
can have profoundly different effects on physiological activation across individuals or circumstances (Cacioppo et al., 2000; Kosslyn et al., 2002~. Cardiovascular, electrodermal, and respiratory activity respond in different ways to various psychological states and behaviors.
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From page 83... ...
Polygraph theories assume that differences in physiological responses are closely correlated with psychological differences between examiners' responses to relevant and comparison questions on the polygraph test. This assumption will be less plausible to the extent that a polygraph testing procedure gives an examiner discretion in selecting the relevant and comparison questions for each examinee.
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From page 84... ...
This format provides information about the likelihood of a physiological response given a person who is being deceptive. Such evidence is commonly offered to address the question of how good the polygraph test is as a diagnostic of lying.
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From page 85... ...
However, as we have shown, the physiological measures used in polygraph testing do not have such close correspondence with deception or any other single psychological state (Davis, 1961; Orne, Thackray, and Paskewitz, 1972~. Lacking a one-to-one correspondence between the psychological and physiological states, empirical evidence at the aggregate level showing that deception produces larger physiological responses than honest responding does not adequately address the validity of the reverse inference, that larger physiological responses can be caused only by deception.
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From page 86... ...
For such conditions to threaten the validity of the test, they would have to differentially affect responsiveness to relevant and comparison questions (e.g., by reducing a guilty examinee's responsiveness to relevant questions)
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From page 87... ...
This uncontrolled variation is likely to reduce the test-retest reliability of polygraph tests when different examiners are used for different tests and to make the accuracy of test results more variable in test formats that depend on creating an emotional climate based on the examiner's judgment. It also creates extreme difficulty in correcting for the effects of social interaction factors on polygraph test results.
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From page 88... ...
. This research typically demonstrates these effects during task performance but not during baseline or resting periods, suggesting the possibility that physiological responses to relevant and comparison questions might be differentially affected on polygraph tests.
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From page 89... ...
Specifically, they suggest that if either the examiner or the examinee bears a stigma, the examinee may exhibit heightened cardiovascular responses during the polygraph testing situation, particularly during difficult aspects of that situation such as answering relevant questions, independently of whether he or she is answering truthfully. Such responses would be likely to increase the rate of false positive results among examinees who are members of stigmatized groups, at least on relevant-irrelevant and comparison question tests.~5 (In Chapter 4, we discuss the very limited empirical research examining the effects of stigma-related characteristics of examiners and examiners, such as race and gender, on the accuracy of polygraph diagnoses of deception.)
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From page 90... ...
. Similarly, examiners with high expectancies of truthfulness might elicit weaker physiological responses, resulting in a high rate of false negatives (lower sensitivity)
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From page 91... ...
The usual strategy for addressing systematic error resulting from a testing interaction is to standardize the interaction, perhaps by automating it. However, this strategy might be very difficult to implement effectively, especially with comparison question polygraph testing, because elements of the interaction are integral to creating the expectations and emotional states in the examinee that are said to be necessary for accurate comparison of responses to relevant and comparison questions.
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From page 92... ...
However, for the most part, polygraph research has focused on a few physiological responses for which measures have been available since at least the 1920s and tried to make the best of them by testing variations of them in practice, without doing much to develop the underlying science. The research has tended to focus on the application without advancing the basic science.
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From page 93... ...
The situation is somewhat different with research on concealed information polygraph testing, which has consistently drawn on the theory of the orienting response. This research has emphasized developing and testing procedures that are resistant to threats to validity that can arise from differential reactions to relevant and comparison questions among examiners who have no event-related information to conceal.
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From page 94... ...
. We found no study of the mechanisms by which such variables might affect polygraph test outcomes: for instance, of the effects they might have on the selection of comparison questions, on the examinee's understanding of the questions and the examination, or on the examiner's behavior, subtle and otherwise, during the examination.
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From page 95... ...
(This approach to interpreting information from polygraph tests is discussed further in Chapter 7.) The other field that polygraph research has not for the most part benefited from is the science of psychological measurement.
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From page 96... ...
Indeed, as already noted, it is rarely clear exactly what polygraph tests are designed to measure, or how the various pieces of data obtained from polygraph tests are thought to be linked to states or attributes of the examiner, making it difficult to even initiate the process of construct validation (Fiedler et al., in press)
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From page 97... ...
Those studies have not led to significant changes in practice. To the extent that the polygraph instrument measures physiological responses relevant to deception, this approach holds promise, but much of that promise has yet to be realized (see Appendix F)
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From page 98... ...
Polygraph research, which has focused mainly on making incremental improvements in the way 1920s technology is used, would seem particularly unattractive to any young scientist wanting to advance understanding of modern psychology or physiology. As a result, there have been few new ideas for the research on the psychophysiological detection of deception.
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From page 99... ...
The fact that polygraph testing combines a diagnostic test and an interrogation practice in an almost inextricable way would be a major concern for any scientist seeking to validate the diagnostic test. The cultures of those parts of the agencies that deal with law enforcement and counterintelligence do not include traditions of scientific peer review, open exchange of information, and open critical debate that are common in scientific work.
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From page 100... ...
A stronger theoretical base is needed for the entire range of polygraph applications. Basic polygraph research should consider the latest research from the fields of psychology, physiology, psychiatry, neuroscience, and medicine; comparison among question techniques; and measures of physiological research.
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From page 101... ...
However, the science indicates that there is only limited correspondence between the physiological responses measured by the polygraph and the attendant psychological brain states believed to be associated with deception in particular, that responses typically taken as indicating deception can have other causes. · The accuracy of polygraph tests can be expected to vary across situations because physiological responses vary systematically across examinees and social contexts in ways that are not yet well understood and that can be very difficult to control.
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From page 102... ...
· The bulk of polygraph research can accurately be characterized as atheoretical. The field includes little or no research on a variety of variables and mechanisms that link deception or other phenomena to the physiological responses measured in polygraph tests.
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From page 103... ...
Most polygraph researchers now consider the technique fundamentally flawed on a theoretical level (e.g., Raskin and Honts, 2002~. For this point to apply under orienting theory, it is necessary to assume that the orienting response is stronger for the specific issues covered by the relevant questions than for the issues evoked by the more generic comparison questions.
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From page 104... ...
Efforts to standardize the interview process and the specific relevant and comparison questions across examinations can be helpful in this regard, and there is some such standardization in some tests, such as the Test of Espionage and Sabotage, that are used in federal employee screening programs. In addition, the concealed knowledge test approach rules out the possibility that extraneous factors may elicit differential responses to relevant and comparison questions by innocent examiners because they have no way of knowing which are the relevant questions.
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From page 105... ...
17. This problem may be less serious for concealed knowledge tests than for other test formats because innocent examiners in that format cannot discriminate between relevant and comparison questions.
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