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 region of interest (TH ROI ) on a user's face; a sensor configured to provide measurements (M) indicative of times at which the user touches the region of interest (ROI); whereby touching the ROI affects TH ROI ; and a computer configured to detect the physiological response based on TH ROI and M.