details—sometimes following carefully specified procedures—because they can affect test results.

Polygraph examination procedures often explicitly combine and interweave testing and interviewing. When a polygraph chart indicates something other than an ordinary nondeceptive response to a relevant question, the examiner typically pursues this response with questioning during the course of the examination. For example, the examiner may say, “You seem to be having a problem in the area of X [the relevant item]” and ask the examinee if he or she can think of a reason for having a strong physiological reaction to that question. The interview may reveal a misunderstanding of the question, which is then explained and reasked in a subsequent charting. Or if the reaction remains unexplained to the examiner’s satisfaction, the issue may be probed in more detail in the interview or with questions in a subsequent charting. Some examiners believe that an important use of polygraph testing is in helping narrow the range of issues that need to be investigated, using both polygraph and other investigative tools.

The important role of interview conditions is also recognized in much of the practice and lore of polygraph testing. For example, it is widely and plausibly believed that polygraph results are different for “friendly” and “unfriendly” examinations (e.g., examiners proffered by the defense or by the prosecution in criminal cases). Presumably, examinees are more relaxed with “friendly” examiners and less likely to have responses that indicate deception on the test. When interviewers are hostile or aggressive, examinees may be less relaxed and may produce different physiological responses than those they would produce in response to calm, friendly questioning.

Such effects of the interview situation are common in other settings, for example, the widely noted phenomenon of “white-coat hypertension,” in which blood pressure is believed to increase because of the context of a medical examination. These situational effects represent a challenge to the validity of any physiological test that does not adequately reduce the influence of variations in the interview situation on the physiological responses being measured or separate the effects of the situation from the effects of the condition (such as deception) that the test is intended to measure. 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. Whether these procedures in fact have the desired effects is an empirical question, which is explored in this book.⁵