The Polygraph and Lie Detection (2003) / Chapter Skim
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5 Evidence from Polygraph Research: Quantitative Assessment
5 Evidence from Polygraph Research: Quantitative Assessment
Pages 121-153
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From page 121... ...
Finally, we address several factors that might affect the accuracy of polygraph testing, at least with some examinees or under some conditions, including individual differences in physiology and personality, drug use, and countermeasures. SPECIFIC-INCIDENT POLYGRAPH TESTING Laboratory Studies For our analysis, we extracted datasets from 52 sets of subjects in the 50 research reports of studies conducted in a controlled laboratory testing environment that met our criteria for inclusion in the quantitative analysis (see Appendix G)
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From page 122... ...
Although samples drawn from these sources are not demographically representative of any population on which polygraph testing is routinely performed, neither is there a specific reason to believe such collections of examiners would be either especially susceptible or refractory to polygraph testing. Since the examiners thus selected usually lack experience with polygraph testing, we will loosely refer to the subjects from these studies as "naive examiners, untrained in countermeasures." The degree of correspondence between polygraph responsiveness of these examiners and the special populations of national security employees for whom polygraph screening is targeted is unknown.
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From page 123... ...
Second, with few exceptions, the points fall well below the upper lefthand corner of the figure indicative of perfect accuracy. No formal hypothesis test is needed or appropriate to demonstrate that errors are not infrequent in polygraph testing.
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From page 124... ...
One factor on which there has been much contention in the research is test format, specifically, comparison question versus concealed information test formats. Proponents of concealed information tests claim that this format has a different, scientifically stronger rationale than comparison question tests in those limited
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From page 125... ...
Specifically, the median accuracy index among 13 concealed information tests was 0.88, with an interquartile range from 0.85 to 0.96, while the corresponding median for 37 comparison question tests was 0.85, with an interquartile range from 0.83 to 0.90. (Two research reports did not fit either of these two test formats.)
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From page 126... ...
(The interquartile range of accuracy indexes for all 59 datasets, laboratory and field, was from 0.81 to 0.91, the same range as for the laboratory studies alone.) In the next section, we discuss what these data suggest for the accuracy of the full population of polygraph tests in the field.
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From page 127... ...
If, as we believe, the polygraph is closely analogous to a clinical diagnostic test, then both psychophysiological theories of polygraph testing and experiences with other clinical diagnostic tests offer useful insights regarding the external validity of laboratory polygraph accuracy for field contexts. Each perspective raises serious concerns about the external validity of results from laboratory testing in the field context.
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From page 128... ...
and concealed information (Ben-Shakhar and Elaad, 2003) tests, but there are limitations to both analyses that preclude drawing any definite conclusions.3 In the papers we reviewed, only one of the laboratory models under which specific-incident polygraph testing was evaluated included stakes that were significant to the subjects' future outside the polygraph room and so similar to those in field applications (Ginton et al., 1982~.
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From page 129... ...
In view of the above issues, we believe that the range of accuracy indexes (A) estimated from the scientifically acceptable laboratory and field studies, with a midrange between 0.81 and 0.91, most likely overstates true polygraph accuracy in field settings involving specific-incident investigations.
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From page 130... ...
. These relevant questions are arguably more similar to comparison questions, which also ask about generic past actions, than is the case in specific-incident testing.
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From page 131... ...
All three studies share biases that make their results less convincing than those statistics indicate. Deceptive examinees were instructed to confess immediately after being confronted, but nondeceptive examiners whose polygraph tests indicated deception were questioned further, in part to determine whether the examiner could find explanations other than deception for their elevated physiological responses.
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From page 132... ...
Brownlie, Johnson, and Knill (1998) reported a study of 769 relevant-irrelevant polygraph tests of applicants for security positions at Atlanta International Airport between 1995 and 1997.
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From page 133... ...
These studies do not provide strong evidence for the validity or utility of polygraph screening. First, the level of accuracy in distinguishing deceptive from nondeceptive examinees in these studies was generally lower than that achieved in comparison question test and concealed information test studies focused on specific-incident investigation.
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From page 134... ...
. One of the earliest reported individual differences in a psychophysiological measure that was meaningfully associated with behavior is in electrodermal lability (Crider and Lunn, 1971~.
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From page 135... ...
Various theoretical rationales have been offered for expecting that the investigated traits might affect physiological responses during polygraph testing. Studies have been conducted comparing individuals in normal populations who are "high" and "low" on personality dimensions, such as trait anxiety (Giesen and Rollison, 1980)
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From page 136... ...
of the participants in situations like polygraph examinations might affect polygraph test results. However, relatively little work has been done to test these theories in the context of polygraph examiner-examinee interactions.
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From page 137... ...
found gender differences in specific physiological responses during polygraph tests, but the differences were not consistent across studies. The effect sizes in these gender studies are rarely calculable.
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From page 138... ...
This evidence is too limited to draw any strong conclusions about whether examiners' expectancies affect polygraph test accuracy. There is a small body of research on the effects of examiners' expectancies, conducted in part to test the hypothesis that so-called stimulation tests, which are intended to convince examiners of the polygraph's ability to detect deception, improve detection accuracy.
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From page 139... ...
The subjects tested have been exclusively undergraduates, dose-response effects have not been evaluated, and the mock crimes have been highly artificial with no consequence for detection. The weight of the published evidence suggests little or no drug effects on the detection of deception using the concealed information test, but given the few studies performed, the few drugs tested, and the analogue nature of the evidence, a conclusion that drugs do not affect polygraph validity would be premature.
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From page 140... ...
Because countermeasures might influence test outcomes and personnel actions, and because the effects of countermeasures on test validity and utility might depend on the examiner's ability to detect these behaviors, it is important to examine the empirical research on the effects and the detectability of physical and mental countermeasures. Rationale Most methods of polygraph examination rely on comparisons between physiological responses to relevant and comparison questions.
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From page 141... ...
Nor is it clear whether examiners can learn to replicate faithfully their responses to comparison questions when answering relevant questions: systematic differences between comparison and relevant responses, even those that are not part of the standard scoring criteria for evaluating polygraph charts, might make it possible to detect countermeasures. Most studies of countermeasures have focused on the effects of these measures on test outcomes and on the accuracy of polygraph tests, without directly examining whether these measures in fact produced their desired physiological effects.
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From page 142... ...
These studies have rarely stated or tested predictions about the effects of specific classes of drugs on specific physiological readings obtained using the polygraph, on the examiner's interpretations of those readings, or of other behaviors observed during a polygraph examination. Different classes of drugs are likely to affect different physiological responses, and the effects of one class of drugs (e.g., benzodiazepines used to treat anxiety)
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From page 143... ...
First, all of the studies have involved mock crimes and most use experimenters or research assistants as polygraph examiners. The generalizability of these results to real polygraph examinationswhere both the examiner and the examinee are highly motivated to achieve their goals (i.e., to escape detection and to detect deception, respectively)
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From page 144... ...
The first step in evaluating countermeasures should be a determination of whether they have their intended effects on the responses measured by the polygraph, followed by a determination of whether these specific changes in physiological responses affect the outcomes of a polygraph test. Countermeasure studies usually omit the step of determining whether countermeasures have their intended physiological effects, making any relationships between countermeasures and polygraph test outcomes difficult to evaluate.
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From page 145... ...
Unfortunately, this work shares the same limitations as the work suggesting that countermeasures have a substantial effect and is based on many of the same studies. There have been reports of the use of mechanisms to detect countermeasure in polygraph tests, notably, reports of use of motion sensors in some polygraph equipment to detect muscle tensing (Maschke and Scalabrini, no date)
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From page 146... ...
Examinees who are highly motivated to "pass" their polygraph tests might engage in a variety of behaviors they believe will improve their chances, including the use of countermeasures. It is therefore reasonable to expect that the people who engage in countermeasures include, in addition to the critical few who want to avoid being caught in major security violations, people who are concerned that their emotions or anxieties (perhaps about real peccadilloes)
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From page 147... ...
Authors such as Maschke and Williams suggest that effective countermeasure strategies can be easily learned and that a small amount of practice is enough to give examiners an excellent chance of "beating" the polygraph. Because the effective application of mental or physical countermeasures on the part of examiners would require skill in distinguishing between relevant and comparison questions, skill in regulating physiological response, and skill in concealing countermeasures from trained examiners, claims that it is easy to train examiners to "beat" both the polygraph and trained examiners require scientific supporting evidence to be credible.
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From page 148... ...
The accuracy index of the laboratory studies of specific-incident polygraph testing that we found that had at least minimal scientific quality and that presented data in a form amenable to quantitative estimation of criterion validity was between 0.81 and 0.91 for the middle 26 of the values from 52 datasets. Field studies suggest a similar, or perhaps slightly higher, level of accuracy.
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From page 149... ...
The studies report accuracy levels comparable to various diagnostic tests used in medicine. We note, however, that the performance of medical diagnostic tests in widespread field applications generally degrades relative to their performance in validation studies, and this result can also be expected for polygraph testing.
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From page 150... ...
These results indicate the need for caution in adopting screening protocols that encourage investigators to follow up on some issues and ignore others on the basis of physiological responses to specific questions on polygraph charts. There are no studies that provide even indirect evidence of the validity of the polygraph for making judgments of future undesirable behavior from preemployment screening tests.
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From page 151... ...
Basic physiological theory suggests that training methods might allow individuals to succeed in employing effective countermeasures. Moreover, the empirical research literature suggests that polygraph test results can be affected by the use of countermeasures.
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From page 152... ...
Its overall results were generally consistent with ours, but it did find positive associations of accuracy with three moderator variables: number of sets of relevant and comparison questions, the presence of motivational instructions or monetary incentives, and the presence of the requirement that deceptive examiners make a deceptive answer (rather than a nonresponse)
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From page 153... ...
With concealed information tests, however, it can only be used by examiners who have concealed information because only they can distinguish relevant from comparison questions.
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