Abstract
The history of research into psychophysiological measurements as an aid to detecting lying, widely known as the ‘lie detector’ or polygraph, is the focus of this review. The physiological measurements used are detailed and the debates that exist in regards to its role in the investigative process are introduced. Attention is given to the main polygraph testing methods, namely the Comparative Question Test and the Concealed Information Test. Discussion of these two central methods, their uses and problems forms the basis of the review. Recommendations for future research are made specifically in regards to improving current polygraph technology and exploring the role of the polygraph in combination with other deception detection techniques.
J. Synnott et al. remember; e.g. What weapon was the victim murdered with?. One of the possible answers presented to the examinee is correct (e.g. the actual murder weapon: a steakknife) while the remaining answers are false, distinct but equally plausible alternatives (e.g. a handgun, a steel pipe, a rifle, an axe, etc.).
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The number of questions to be asked depends largely on how much of the available crime-related investigation lends itself to being formulated into questions. In this, one important factor to consider is memory, as research has shown that peripheral details of a crime (e.g. the number of chairs a room) are easily forgotten over time by both the guilty and the innocent, while memories of central details of a crime (e.g. the murder weapon) are more readily retained by the guilty (Gamer, 2010). The number of possible answers to allocate to each question depends on a number of factors. First and foremost, to an uninformed examinee, each answer must seem equally plausible, and there may be a limited number of plausible answers to a given question, e.g. there are only so many equally distinct and plausible murder weapons. By having a number of uninvolved and uninformed individuals review the possible answers, an examiner can ensure that none stand out. Secondly, certain types of information h
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, 2005).
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Furthermore, answers may be perceived as significant by an examinee, and subsequently elicit an orienting response, for reasons other than it being recognized as the correct answer, e.g. an examinee may have an orienting response at the mention of a gun due to a past traumatic experience involving a gun, such as getting robbed at gunpoint. An examiner cannot always foresee whether certain answers may be of incidental significance to the examinee, which is why the pre-test interview should address this issue so that inappropriate questions and answers can be removed before the actual testing phase (Krapohl, McCloughan, & Senter, 2009). Generally speaking, having a greater number of possible answers (usually 5 or 6) is advantageous as it reduces the risk of an unknowing examinee physiologically responding to the correct answer by chance, therefore reducing the rate of false positives in a statistically reliable manner (Ben-Shakhar, BarHillel, & Kremnitzer, 2002; Elaad, 1999).
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