Emotional arousal predicts pupil responses following a single attention shift between bright and dark moving stimuli

Pupil size is widely used as an index of emotional arousal but is also strongly influenced by luminance and attention to bright or dark stimuli. We examined whether trial-by-trial subjective emotional ratings predicted pupil responses when affective sound onset coincided with a single attention shift between bright and dark moving stimuli. Twenty-two participants listened to affective environmental sounds while viewing two superimposed moving dot fields, one bright and one dark, moving in opposite directions. At sound onset, participants shifted attention between the dot fields and maintained attention during the 6 s sound. They then rated each sound for arousal and valence. Using subtractive change from the 500 ms pre-sound baseline as the primary pupil measure, trial-by-trial arousal was positively associated with pupil responses from 0.75 to 5.95 s after sound onset, surviving false-discovery-rate correction. Valence also showed a significant negative association with pupil responses after adjustment for arousal. The arousal association remained robust across sensitivity analyses, although the within-sound analysis was not significant. The arousal-by-block interaction was not significant, providing no evidence that the arousal–pupil association differed between attention-shift conditions. These findings indicate that subjective arousal was associated with trial-by-trial pupil variation within a visual-attentional context involving concurrent changes in attended luminance.