Abstract
We tested the accuracy of thermal imaging as a lie detection tool in airport screening. Fifty-one passengers in an international airport departure hall told the truth or lied about their forthcoming trip in an interview. Their skin temperature was recorded via a thermal imaging camera. Liars’ skin temperature rose significantly during the interview, whereas truth tellers’ skin temperature remained constant. On the basis of these different patterns, 64% of truth tellers and 69% of liars were classified correctly. The interviewers made veracity judgements independently from the thermal recordings. The interviewers outperformed the thermal recordings and classified 72% of truth tellers and 77% of liars correctly. Accuracy rates based on the combination of thermal imaging scores and interviewers’ judgements were the same as accuracy rates based on interviewers’ judgements alone. Implications of the findings for the suitability of thermal imaging as a lie detection tool in airports are discussed.
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Notes
Passengers who did not take part gave good reasons to do so: They were busy (had work or shopping to do), travelled with more people or had to catch their flight. The reasonably high response rate may have been a combination of an official looking experimenter combined with the opportunity to earn money and serving a good cause (scientific research that could be used to enhance security at airports).
These questions were asked to establish the ground truth in the experiment. All participants (truth tellers and liars) were asked to reveal their true destination during the actual interview, and truth tellers were also asked to reveal the true purpose of their trip. When we compared the answers during the actual interview with the answers given to the experimenter, we noticed that all interviewees honestly reported their destination, and that all truth tellers honestly reported the true purpose of their trip.
A logistic regression analysis revealed similar results. That is, the results for baseline and Phase 1 were not significant, but the results for Phases 2 and 3 were significant. When we entered Phase 3 and the interviewers’ veracity judgement in the regression analysis, the interviewers’ judgement variable emerged as the only predictor.
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Warmelink, L., Vrij, A., Mann, S. et al. Thermal Imaging as a Lie Detection Tool at Airports. Law Hum Behav 35, 40–48 (2011). https://doi.org/10.1007/s10979-010-9251-3
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DOI: https://doi.org/10.1007/s10979-010-9251-3