of communication. These channels, in turn, can be monitored by a detector's unaided perceptual processes. When one or more channels provide cues that “betray” the person's deceptions, researchers claim that leakage has occurred.

Within this framework, several possibilities arise. The simplest is that deception leaks in predictable ways for all people regardless of differences in experience or culture: the predictability would derive from a fixed set of communication cues, such as body movements, rather than facial expressions. More complicated are the possibilities that a variety of behavioral patterns are diagnostic, depending on a person's experience, training, and cultural background or the particular circumstances under which he or she is being observed. Moreover, it is possible that individuals are conscious about such cues and can manage the expressions or movements being monitored by an observer.

This chapter reviews ongoing research programs that focus on those issues: what has been learned from laboratory studies on deception and what needs to be learned through further experimental research. (The next chapter is more conceptual, reviewing various taxonomies and frameworks designed to broaden the concept of deception.) We also discuss the issue of cultural and other subpopulation differences in the interpretation and execution of deception in the context of generality of findings obtained in laboratory studies with American subjects.

PHYSICAL INDICATORS AND PSYCHOLOGICAL STATES

Although the problem of inferring specific psychological states from specific observed behaviors is quite complex, there is little doubt about the existence of linkages between internal states and external behaviors. A large research literature on nonverbal behaviors associated with emotions and intentions has made apparent the value of using such behaviors as windows on underlying psychological states.1 The focus of this section is more specialized: to draw on relevant parts of the large literature on nonverbal behaviors for insights and suggestions for research on nonverbal indicators of deception.

The Laboratory Paradigm

Most of the contemporary experimental research on deception involves the communication of false verbal statements made with intent to deceive. Researchers are interested in the cues sent by deceivers and the cues used by receivers to detect deception; the cues consist, for the most part, of nonverbal behaviors coded systematically from replays of videotaped simulated performances (speeches, interviews), usually en-



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