1. A system configured to detect a physiological response, comprising: an inward-facing head-mounted thermal camera (CAM) configured to take thermal measurements of a first region of interest (TH ROI1 ) on a user's face; an inward-facing head-mounted visible-light camera (VCAM) configured to take images of a second region of interest (IM ROI2 ) on the face; wherein the first region of interest (ROI 1 ) and the second region of interest (ROI 2 ) overlap; and a computer configured to detect the physiological response based on TH ROI1 , IM ROI2 , and a model.