An orienting response occurs in response to a novel or personally significant stimulus to facilitate a possible adaptive behavioral response to the stimulus (Sokolov, 1963; Kahneman, 1973). The phenomenon of orienting is illustrated in a cocktail party in which a person can converse with another, apparently oblivious to the din created by the conversations of others, yet the person stops and orients toward the source when his or her name is spoken in one of these other conversations. Lynn (1966) has summarized the physiological profile of an orienting response as decreased heart rate, increased sensitivity of the sense organs, increased skin conductance, general muscle tonus (but a decrease in irrelevant muscle activity), pupil dilation, vasoconstriction in the limbs and possibly vasodilation in the head, and more asynchronous, low-voltage electrical activity in the brain. There are individual differences in the presence and relative magnitude of these responses, however, and the orienting response is subject to habituation, which implies that false negatives may be particularly likely among the most sophisticated and well-prepared examinees.

The concealed information test format is designed to provide a quantitative specification of the relative probability of a given outcome based on the elicitation of an orienting response to a specific piece of information that differs from the other items only in the mind of an individual who is knowledgeable about details of a crime or other target incident. An innocent examinee would be expected to respond most strongly to the relevant item in a series of five similar items (e.g., “How much money was taken? $10, $20, $30, $40, $50”), by chance with a probability of 1 in 5 (0.20). Such a response on one question would not engender much confidence in the interpretation that the person had concealed knowledge of the true amount. However, if an examinee consistently responded most strongly to the one relevant item out of five, over five separate questions, then the probability of that combined outcome occurring by chance in the absence of concealed information is presumed to be 1 in 55 (0.00032).

It is important to keep in mind that there might be a distinction between physiological reactions to the stimuli (i.e., the questions) and reactions to the response (e.g., attempted deception). Arousal theory and orienting theory, both of which are commonly cited as justifications for the concealed information test format and related techniques, focus on reactions to the questions. From the perspective of these theories, it might not even be necessary for examinees to respond, and reactions might be the same regardless of whether the response is deceptive or honest. The theories that underlie the comparison question technique (e.g., set theory, theory of conflict, conditioned response theory) 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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