Can We Deceive the Polygraph Test?
In our current society, we place a premium on honesty, and with that we have attempted to develop methods that can detect deception. We have all seen television shows, like Maury or Making a Murderer, that have made use of the results of a lie-detector test. Namely, the polygraph test is one of the most controversial tests that is still used, although limitedly. Through all of this controversy, the polygraph test is no longer admissible as evidence in the court of law due to a lack of reliability, although it still has many applications, including in employment screening. Upon discovering this, I sought to investigate the controversies surrounding this test in order to attempt to understand why we would be able to use it in some contexts, but not others.
A polygraph test uses physiological indices of autonomic arousal in order to detect the construct of lying. The instrument measures heart rate, blood pressure, respiration and skin conductivity. Among the common questioning techniques are the Control Question Test and the Guilty Knowledge Test. The Control Question Test aims to contrast responses to relevant questions with those of neutral and irrelevant questions in an attempt to judge deception (National Academy of Sciences, 2002). The Guilty Knowledge test measures the physiological response to questions regarding information that only a guilty suspect could know (National Academy of Sciences, 2002). The theoretical basis surrounding the polygraph is that greater physiological arousal compared to a baseline arousal would indicate that the subject is not telling the truth.
The validity of this technique has often been questioned on the basis that there is no evidence that autonomic arousal uniquely translates into deception. There is not a characteristic pattern of physiological arousal that can be related back to the act of lying. Upon researching this topic, I came across many psychological and physical factors that can affect the accuracy of the polygraph test. For example, research has shown that individuals who are anxious or who feel threatened while taking the polygraph test can lead to false positives, indicating that the individual was lying, when in fact they were being honest (Saxe et al., 1985). Another threat to the accuracy of the polygraph test is the use of countermeasures. Individuals can partake in mental and/or physical acts that decrease the accuracy of the polygraph, causing false negatives. For example, a study conducted by Honts et al., investigated the impact of the utilization of the countermeasures on the polygraph accuracy using the Control Question Test technique. The participants were either guilty or innocent and they engaged in either physical or mental countermeasures. The physical countermeasures included muscle tension (pressing toes to the floor), pain (biting the tongue) or a combination. The mental countermeasure included mental arithmetic (count backwards by 7s) during the response to the control question. The results showed that 50% of the guilty individuals defeated the polygraph test from engaging in these countermeasures (Honts et al., 1994). The main mediating mechanism of these countermeasures was that they altered cardiovascular output, allowing them to deceive the lie-detector test (Honts et al., 1994). Moreover, the expert conducting the polygraph test was only able to detect the use of a countermeasure by the participant 12% of the time for the physical countermeasures and was completely unable to detect the use of mental countermeasures (Honts et al., 1994). The use of physical and mental countermeasures was proven to be equally effective in misleading the polygraph. These results pose serious doubts on the applicability of these lie detector tests, as simple techniques like the countermeasures can not only be employed but are also rarely detected and decrease the accuracy of the polygraph significantly. Furthermore, as both false negative and false positives are prevalent among the literature, the reliability of this test is reduced, thereby posing a possible ethical issue. In terms of applicability, even though judicial decisions are of higher consequence for errors in a polygraph, thereby deeming it inadmissible for the most part in the court of law, a polygraph should not bear weight in the employment screening process, as being turned away from a job on the basis of a measure with limited validity can be deemed potentially unethical as this impacts one’s life course.
References
Honts, C. R., & Kircher, J. C. (1994). Mental and physical countermeasures reduce the accuracy of polygraph tests. Journal of Applied Psychology, 79(2), 252.
National Academy of Sciences (2002). The polygraph and lie detection. Washington, DC: National Academy Press.
Saxe, L., Dougherty, D., & Cross, T. (1985). The validity of polygraph testing: Scientific analysis and public controversy. American Psychologist, 40(3), 355.
