Sensory processing traits and the temporal dynamics of the pupillary light reflex in young adults from the general population: A generalized additive mixed model analysis

Dunn’s sensory processing framework captures substantial individual variability in everyday sensory responsivity and regulation. Prior physiological findings, however, have been mixed, potentially because complex responses are often reduced to single scalar metrics. We investigated how sensory processing traits relate to the temporal dynamics of the pupillary light reflex (PLR) in 39 nonclinical young adults. Participants completed the Adolescent/Adult Sensory Profile (AASP) and clinical scales indexing autism traits, ADHD symptoms, depression, and anxiety. PLR was recorded to 100-ms full-field flashes of four colors (White, Red, Green, Blue). Proportional pupil change over 0–3 s post-stimulus was analyzed using generalized additive mixed models, allowing flexible nonlinear time-by-trait effects while accounting for within-trial autocorrelation and subject-level random effects. Sensory traits showed no reliable main effects on average response level, whereas nonlinear time-by-trait effects were significant for both Dunn axes (Low Threshold and Active Strategy), indicating trait-related modulation of waveform shape. In supplementary quadrant analyses, Sensation Avoiding showed the largest overall waveform differences, consistent with broadly attenuated constriction across the time course and recovery-phase modulation. These patterns remained after adjusting for stimulus physical properties (luminance and melanopic DER) and co-occurring psychological symptoms. The results highlight the value of modeling the continuous temporal structure of PLR waveforms to detect individual-difference signatures of sensory processing traits.