Swedish researchers at Karolinska Institute have discovered that breathing directly affects pupil size. During inhalation, the pupils are the smallest and, during exhalation, they are the largest. This breathing-related mechanism can potentially influence vision and is unique because it operates cyclically without external stimuli. Furthermore, it functions alongside the three previously known factors affecting pupil size: light intensity, focus distance, and cognitive factors.
Through five experiments with over 200 participants, researchers confirmed this effect persists across various breathing patterns, lighting conditions, and activities, with the size difference between breathing phases being significant enough to theoretically impact vision. The researchers hypothesize that this breathing-pupil relationship may represent an evolutionary adaptation that optimizes vision, alternating between detail perception during inhalation and faint object detection during exhalation. Looking forward, these findings could lead to new diagnostic methods for neurological conditions like Parkinson’s disease.
Image credit: Gorodenkoff / iStock