Forehead thermal signature extraction in lie detection.

Previous work demonstrated that facial thermography can be successful in lie detection. In those studies the development was based on the thermal signature of the periorbital region. In the present paper a new source of psycho-physiological information is proposed: the forehead. We found that the corrugator muscle in the forehead is more active than usual, when the individual experiences sustained stress. As a result, more blood flows through the supraorbital vasculature, increasing the cutaneous forehead temperature. In order to monitor the thermal signature of the forehead's cutaneous tissue, a segmentation method based on active contours has been developed. This creates a virtual forehead probe that can monitor stress levels by measuring thermal radiation over the supraorbital vessels. Thermal videos of 38 subjects under interrogation for a mock crime scenario were used to test the new approach. The results show that the recovered forehead signal, enables 76.3% success rate in deceptive state classification. Thus, the forehead channel shows promise in lie detection.