General state countermeasures may include the use of drugs and biofeedback to alter physiological state. Specific point countermeasures include mental imagery and physical measures such as counting or biting the tongue. With the concealed information test for improving polygraph reliability, countermeasures must produce equivalent physiological responses to all questions, either through hyperresponsivity or hyporesponsivity. Thus, general state countermeasures might be expected to be more effective in producing false negatives. With control question approaches, an effective countermeasure must reverse differential physiological responses so that a guilty individual produces larger physiological responses to control than to relevant questions. Results of some field research and laboratory studies suggest that general state countermeasures are, in fact, not significantly effective against either type of test approach, while a number of specific point countermeasures can produce significant false negatives. However, the development of statistical decision models for the detection of countermeasures could lead to a reduction in errors and improved accuracy of PDD techniques. 21 references.