INTRODUCTION: Pupil size adaptation is a well-established marker of autonomic nervous system activity that offers valuable insights into physiological correlates of both sensory and emotional processing in a nonobtrusive way.

AIM(S): The present study investigates whether basic visual stimuli with increasing luminance can induce different autonomic responses in individuals with varying levels of sensory processing sensitivity.

METHOD(S): We used light ramps—grayscale full-screen images created in which luminance increased gradually in fixed increments, creating a transition from low to high salience. These stimuli were designed to isolate luminance-driven responses while minimizing cognitive load and distraction. We have tested 105 participants (55 women). To display the stimuli, we used an HTC Vive Pro headset with a dedicated 200Hz Pupil Labs eye-tracking system to record the pupil size. Sensory Processing Sensitivity was measured using the Highly Sensitive Person Scale for research purposes.

RESULTS: Pupil responses were significantly influenced by stimulus intensity progression and baseline pupil size, showing a pronounced nonlinear adaptation pattern across increasing luminance. Importantly, Sensory Processing Sensitivity moderated this relationship: individuals with high sensory processing sensitivity scores have significantly weaker pupillary constriction in response to high-luminance displays compared to those with lower sensitivity.

CONCLUSIONS: Attenuated adaptive response suggests a modulation of parasympathetic activity and potentially reduced autonomic adaptability under sensory load. The other possible explanation lies in the elevated activity of the sympathetic nervous system, that could stop the pupil from full constriction. The findings highlight the potential of pupillometry as a non-invasive tool for assessing individual differences in sensory processing and contribute to a growing body of research on the physiological correlates of neurodiversity.

FINANCIAL SUPPORT: This work was supported by the Polish National Science Centre (grant number 2021/41/N/HS6/04490).