The study examines the relationship between pupil diameter and emotional arousal during picture viewing, and how autonomic activation (heart rate and skin conductance) influences these responses. Pupil diameter was measured during picture viewing to assess the effects of hedonic valence and emotional arousal. Autonomic activity was also measured to determine whether pupillary changes were mediated by parasympathetic or sympathetic activation. The results showed that pupillary changes were larger when viewing emotionally arousing pictures, regardless of whether they were pleasant or unpleasant. Pupillary changes during picture viewing covaried with skin conductance changes, supporting the interpretation that sympathetic nervous system activity modulates these changes in the context of affective picture viewing. The data provide strong support for the hypothesis that the pupil's response during affective picture viewing reflects emotional arousal associated with increased sympathetic activity. The study used a modern infrared eye-tracking system and a large set of well-validated pictures from the International Affective Picture System (IAPS) to control for rated pleasure and arousal. The results indicate that pupillary changes covaried with skin conductance reactions, providing collateral support for the hypothesis that pupil diameter during picture viewing predominantly reflects sympathetic nervous system activity. The study also found that heart rate changes were different for unpleasant pictures compared to pleasant or neutral pictures, indicating that cardiac deceleration is generally greater when viewing unpleasant pictures. The findings suggest that emotional arousal is a key element in modulating the pupil's response, and that pupil dilation reflects general, rather than gender-specific, arousal. The study also found that the magnitude of the initial light reflex was modulated by picture luminosity, and that the light reflex was highly correlated with the mean luminosity on a picture-by-picture basis. The results support the more recent consensus that pupil diameter increases when people process emotionally engaging stimuli, regardless of hedonic valence. The study also found that the relationship between skin conductance and pupil changes persisted even when specific effects due to luminosity were removed using hierarchical multiple regression. The findings suggest that emotional arousal is a key element in modulating the pupil's response, and that pupil dilation reflects general, rather than gender-specific, arousal.The study examines the relationship between pupil diameter and emotional arousal during picture viewing, and how autonomic activation (heart rate and skin conductance) influences these responses. Pupil diameter was measured during picture viewing to assess the effects of hedonic valence and emotional arousal. Autonomic activity was also measured to determine whether pupillary changes were mediated by parasympathetic or sympathetic activation. The results showed that pupillary changes were larger when viewing emotionally arousing pictures, regardless of whether they were pleasant or unpleasant. Pupillary changes during picture viewing covaried with skin conductance changes, supporting the interpretation that sympathetic nervous system activity modulates these changes in the context of affective picture viewing. The data provide strong support for the hypothesis that the pupil's response during affective picture viewing reflects emotional arousal associated with increased sympathetic activity. The study used a modern infrared eye-tracking system and a large set of well-validated pictures from the International Affective Picture System (IAPS) to control for rated pleasure and arousal. The results indicate that pupillary changes covaried with skin conductance reactions, providing collateral support for the hypothesis that pupil diameter during picture viewing predominantly reflects sympathetic nervous system activity. The study also found that heart rate changes were different for unpleasant pictures compared to pleasant or neutral pictures, indicating that cardiac deceleration is generally greater when viewing unpleasant pictures. The findings suggest that emotional arousal is a key element in modulating the pupil's response, and that pupil dilation reflects general, rather than gender-specific, arousal. The study also found that the magnitude of the initial light reflex was modulated by picture luminosity, and that the light reflex was highly correlated with the mean luminosity on a picture-by-picture basis. The results support the more recent consensus that pupil diameter increases when people process emotionally engaging stimuli, regardless of hedonic valence. The study also found that the relationship between skin conductance and pupil changes persisted even when specific effects due to luminosity were removed using hierarchical multiple regression. The findings suggest that emotional arousal is a key element in modulating the pupil's response, and that pupil dilation reflects general, rather than gender-specific, arousal.