We applied the use of thermography to cognitive neuropsychology, particularly as an objective marker of subjective experiences, in the context of lying. We conducted three experiments: (a) An important lie was invented by the participants in 3 min, and it was recounted by phone to a significant person while they were recorded by the thermographic camera, obtaining a face and hands map of the lie. (b) A similar methodology was carried out, but adding the Cold Stress Test (CST) of the dominant hand during the phone call, obtaining a second physiologic marker (the percentage of thermal recovery) to detect the lie. Further, it established a control condition where it generated anxiety in the participants using IAPS images with negative valence and high arousal, which were described by phone to a loved one. We obtained results that showed significant correlations between changes in body temperature and mental set. Of particular interest was the temperature of the nose and hand, which tended to decrease during lying (Experiment 1). The participants also showed a lower recovery of the temperature after the CST when they were lying (Experiment 2). (c) Experiment 3 is a replication of Experiment 2 but with a different type of lie (a more ecological task) in a different scenario (following the ACID interview, with the use of the phone eliminated and participants motivated to lie well). The main pattern of results was replicated. We obtained an accuracy of 85% in detection of deception with 25% of false alarms.