Any effectiveness of countermeasures would reduce the accuracy of polygraph tests. There are studies that provide empirical support for the hypothesis that some countermeasures that can be learned fairly easily can enable a deceptive individual to appear nondeceptive and avoid detection by the examiners. However, we do not know of scientific studies examining the effectiveness of countermeasures in contexts where systematic efforts are made to detect and deter them.

There is also evidence that innocent examinees using some countermeasures in an effort to increase the probability that they will “pass” the exam produce physiological reactions that have the opposite effect, either because their countermeasures are detected or because their responses appear more rather than less deceptive. The available evidence does not allow us to determine whether innocent examinees can increase their chances of achieving nondeceptive outcomes by using countermeasures.

The most serious threat of countermeasures, of course, concerns individuals who are major security threats and want to conceal their activities. Such individuals and the organizations they represent have a strong incentive to perfect and use countermeasures. If these measures are effective, they could seriously undermine any value of polygraph security screening. Basic physiological theory suggests that training methods might allow individuals to succeed in employing effective countermeasures. Moreover, the empirical research literature suggests that polygraph test results can be affected by the use of countermeasures. Given the potential importance of countermeasures to intelligence agencies, it is likely that classified information on these topics exists. In open communications and in a classified briefing for some of the committee, we have not been told of any such research, so we cannot verify its existence or relevance.