1. A method for increasing sensitivity of determination of truthfulness in a subject, comprising the steps of: (a) asking the subject a question of interest, allowing the subject to provide a response of interest during a period of interest, wherein it is not known beforehand whether the response of interest is truthful or deceptive, and measuring brain activity of the subject during the period of interest; (b) asking the subject at least once to admit and at least once to deny to the question of interest; (c) measuring the difference in brain activity of at least one brain region between the denial period of interest and the admission period of interest; and (d) optionally repeating steps a) to c).