n.1. the scientific measurement of the pupil of the eye, using a pupillometer (or coreometer) to measure the pupil’s diameter. Also called pupilometrics. 2. a research method in which pupillary responses to stimuli (usually visual images) are measured in order to determine the participant’s interest in the stimuli. [devised by U.S. psychologist Ekhard Hess (1916–1986)]