Lie Detection: Guilty or Innocent?
The use of the polygraph to detect deception among subjects has been largely debated on throughout the years. “Is it more of a myth than it is a reality?” I definitely don’t have the intention to answer this controversial question nor do I feel like it’s necessary to list all the pros and cons associated with both sides of the story. However, there is one thing about the use of polygraphs that is clear: there is no psychophysiological pattern that has been found to be specific to deception (Grubin 2010).
Sure, the idea is a great one: maybe the act of deception changes the psychophysiological patterns within the body and maybe the polygraph can detect these changes when they occur. However, what if nerves are getting the best of the subjects even though they’re innocent (false positives)? Would it be possible to contrast the two reports to determine when lying is occurring and when it’s not? On the other hand, what if the act of deception shows normal psychophysiological patterns (false negatives)? Does that mean lying isn’t really occurring or is the lie just being ‘hidden’ very well? There’s no real way to determine the act of deception using psychophysiological patterns because there is no unique marker of deception, which is the reason why all these questions speak to the poor validity and reliability of polygraph tests.
Besides, stress-induced psychophysiological changes may not only accompany the thought of having to take a polygraph test; it may also accompany examiner’s belief about the examinee. If the examiner strongly believes that the examinee is a criminal (even though he/she may not be), then the examiner might act in ways that could provoke anxious behaviours within the examinee, resulting in the appearance of criminal-like psychophysiological changes, as judged by the polygraph report.
In principle, this idea violates one of the first basic rules that we learn as young researchers in the field of psychology: since experimenters have the power to influence subjects during various studies, it is important to make sure that their manipulations don’t result in subjects feeling the need to behave in ways that are consistent with the experimenters’ thoughts. If the experimenters are creating an anxious environment and causing those psychophysiological changes, they are doing exactly what they’re not supposed to be doing.
Although forensic psychologists may sometimes feel the need to provide polygraph reports when trying to determine whether or not someone is a criminal, I believe that the action of forcing people into these situations and creating an atmosphere that is based on accusations may cause anxious behaviours even in times of innocence. People have quickly understood how to find ways around these changes, but if the physiological changes are indeed present in both anxious criminals and anxious innocents then that might be an indication that the polygraph can detect these changes, but the fact that we don’t have the ability to determine the difference between the two anxious situations and the fact that they are not consistent across situations demonstrates poor validity and reliability, respectively.
References
Grubin, D. 2010. The Polygraph and Forensic Psychiatry. Journal of the American Academy of Psychiatry and the Law. 38(4): 446 –51.
