We applied thermography to cognitive neuropsychology, particularly as a somatic marker of subjective experience during cognitive and emotional tasks. We found significant correlations between changes in facial temperature and mental set. Specifically, the temperature of the nose tended to decrease during emotional tasks and increase during cognitive tasks. However, for stress tests or high arousal reactions to emotional stimuli, the direction of the thermal change depended on the nature of the setting, real or simulated. Detection of deception is a mixed field where cognitive effort, physiological stress, and empathy have evolved, affecting the direction of the thermal variationhigher or lower temperature of the tip of the nose and forehead. We found that the temperature change of the nose and forehead may enable detecting when people lie about facts (the Pinocchio effect markers). In general, one important contribution is to recover mental thermometry as a potent tool for neurocognitive studies.