Some new or additional autonomic measures for detecting deception seem, on theoretical grounds, to be closer than polygraph measures to the psychological phenomena believed to be signals of deception. Some of them, such as facial thermography, may have practical advantages over the polygraph because they may be quicker, easier, or less invasive. Members of this class of measures that have any of these advantages may be promising alternatives to the polygraph that may be worthy of further investigation. They may have only limited value as supplements, however, if in fact they are measuring the same underlying phenomena. If so, their only potential value as supplements would be to help correct for error in polygraph-based estimates of those phenomena.
Functional brain imaging techniques have important advantages over the polygraph, in theory, because they examine directly what the brain is doing. However, they are far from providing a practical alternative or supplement to the polygraph. Part of the limitation is theoretical. Not enough is yet known about the specific cognitive or emotional processes that accompany deception, about their localization in the brain, or about whether imaging signals can differentiate the brain activity associated with these processes from brain activity associated with other processes to make an assessment of the potential validity of these techniques on the grounds of the basic science. Further research with fMRI, coupled with a scientifically based cognitive psychological approach to deception, will be needed to determine if these issues can be addressed. Such research is likely to identify some signals of deception and localize some relevant processes, but not enough is known yet to guess whether the signals will be specific to deception. Functional imaging might also be used in efforts to identify brain signatures of mental activities that might be used as countermeasures to the psychophysiological detection of deception. If a research effort is undertaken to find improved scientific techniques for the detection of deception, basic research on brain imaging would be a top candidate for the research agenda.
There are also major practical problems at present with using brain imaging techniques for the psychophysiological detection of deception. The most likely technique to be used, fMRI, is both time consuming and expensive to perform. A typical research study with fMRI presently takes 2 to 3 hours to perform and many hours thereafter to analyze. Furthermore, almost all research to date has focused on results averaged over groups of individuals. While such an averaging approach is important