The UK Houses of Parliament have an office called POST – Parliamentary Office of Science and Technology - website here
The job of POST is to provide UK MPs with “independent, balanced, and accessible analysis of public policy issues related to science and technology”, in order “to inform parliamentary debate”. POST has recently released a note entitled “Detecting Deception”, which you can find here.
It must be kept in mind that the text is not politically-biased and does not stem from a political decision. It is just meant to be a piece of high-profile, independent scientific information.
The text deals with several aspects of lie-detection technology. As to neuroscientific lie-detection, which is the one form of lie-detection that concerns most the readers of this blog, the report states that “newer studies” on fMRI lie-detection “suggest deception detection can reach 80% accuracy when analyzed at the individual level.”
This is confirmed for instance by Ganis & Keenan (2009). The two neuroscientists report that the best sensitivity fMRI lie-detection can achieve in the lab without generating a mass of false positives (which of course would render the test useless) is 71%. As traditional lie-detection through unaided assessment of purported behavioral cues for deception (gaze aversion, flickering voice, and so on) is not above chance, 71% could already look like a considerable improvement. However, it has been recently proven that this accuracy rate is unable to survive even banal countermeasures. In fact Ganis et al (2011) showed that the reliability of fMRI lie-detection drops to 33%, far worse than chance, if the subject decides to move imperceptibly a finger or a toe. Therefore, the technique is useless when subjects have an interest in hiding their lies, that is to say in most real-life situations to which fMRI lie-detection could be applied.
A second part of the note is worth being mentioned, even though it has little to do with neuroscience. The British Ministry of Justice is performing a mandatory polygraph pilot on sex offenders released on license. The UK government wants to ascertain “whether use of polygraphs increases the disclosure offenders make under supervision and therefore improves how offenders are managed when they have no choice but to be tested.” Previous, more limited pilots had shown that offenders undergoing polygraph testing “gave fuller accounts of offences with fewer instances of denial” and “were more likely to disclose behaviors considered high-risk by probation staff (thus leading to treatment or sanction).”
But it seems to be quite obvious to me that a person undergoing a lie-detection examination will be less likely to lie: Her belief that the technique can actually detect lies will be sufficient to give her a solid motivation to tell the truth. But this is by no means a proof of the polygraph’s real capability of spotting lies. It is just a psychological effect that stems from the fear of being detected when lying. Using whatever kind of imposing mock scientific apparatus would create the same effect in lay subjects.
References
Ganis, G., & Keenan, J. P. (2009). The cognitive neuroscience of deception. Social Neuroscience, 4(6), 465-472.
Ganis, G., Rosenfeld, J. P., Meixner, J., Kievit, R. A., and Schendan, H. E (2011). Lying in the scanner: Covert countermeasures disrupt deception detection by functional magnetic resonance imaging. Neuroimage 55: 312-319
Great post. Empirically speaking, your thoughts on people "undergoing a lie-detection examination will be less likely to lie" is dead on. As I had a former spouse polygraphed about infidelity, the presence of the polygraph alone revealed details that my spouse was still keeping latent for about a year. The polygrapher, Dan, who is over at indepthpolygraphs.com, spoke individually with me and my husband and once alone with him, he confessed to certain issues even before actually being administered a polygraph exam. That "psychological effect" aforementioned is certainly dead on--the fear alone of believing you will be "detected" goes a long way in the entire interview/polygraph process.
Posted by: Susan Finkel | 06/06/2011 at 11:05 AM