Pupillometry (IMAGE) Brigham Young University Caption The researchers used an infrared camera to continuously measure pupil diameter, which is a direct signal of the body's physiological stress response. Credit Jaren WIlkey, BYU Usage Restrictions For use only in news coverage of this study. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.