The automatic change in size of the pupil in response to light. The pupil dilates in low light and constricts in bright light.

PUPILLARY REFLEX: "The pupillary response helps to avoid the temporary loss of sight by being dazzled by bright sunshine."
Cite this page: N., Pam M.S., "PUPILLARY REFLEX," in PsychologyDictionary.org, April 28, 2013, https://psychologydictionary.org/pupillary-reflex/ (accessed October 20, 2021).