for example, the field includes little or no research on the emotional correlates of deception; the psychological determinants of the physiological measures used in the polygraph; the robustness of these measures to demographic differences, individual differences, intra-individual variability, question selection, attempted countermeasures, or social interaction variables in the interview context; or the best ways of measuring and scoring each physiological response for tapping the underlying emotional states to be measured. Because empirical evidence of accuracy does not exist for polygraph testing on important target populations, particularly for security screening, the absence of answers to such theoretical questions leaves important questions open about the likely accuracy of polygraph testing with target populations of interest.
Polygraph research has not been adequately connected to at least two major scientific literatures, other than basic psychophysiology, that are also of direct relevance to improving the psychophysiological detection of deception. One of these is the research on diagnostic testing. As noted in Chapter 2, polygraph researchers and practitioners do not generally conceive of the polygraph as a diagnostic test, nor does most of the field recognize the concept of decision thresholds that is central to the science of diagnostic testing. Researchers and practitioners rarely recognize that the tradeoff between false positives and false negatives can be made as a matter of policy by setting decision thresholds. As a result, practitioners seem to make this tradeoff implicitly, sometimes in the choice of which polygraph testing procedure to use and sometimes, perhaps, in judging the likelihood that a particular examinee will be deceptive. Polygraph research also does not consider systematically the possible use of the polygraph as part of a sequence of diagnostic tests, in the manner of medical testing, with tests given in a standard order according to their specificity, their invasiveness, or related characteristics. (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. Psychological testing and measurement draws on nearly a century of well-developed research and theory (Nunnally and Bernstein, 1994), which has led to the development of reliable and valid measures of a wide range of abilities, personality characteristics, and other human attributes. There is substantial research dealing with the evaluation of objective tests, personality inventories, interviews, and other assessment methods, and clear