Pupil Size Reflects Trial‐Level Variability in Imagery Vividness During Immersive Storytelling but Not (or Hardly) Individual Differences in Trait Imagery

= 115), in which participants read, listened, or freely imagined stories that evoked a sense of darkness or brightness. In addition, self-reports of vividness were collected for each story to measure variations in imagery vividness during the experiment; and through questionnaires (VVIQ, SUIS), to measure differences in task-unrelated imagery abilities at the individual level. We found that the effect of larger pupils for darkness-evoking stories than brightness-evoking stories was highly variable. Importantly, we found that this pupil-size difference (dark-bright) was consistently largest for vividly imagined stories. Finally, we did not find any convincing relationship between this pupil-size difference and individual differences in questionnaire-based imagery. We conclude that the strength of pupil-size changes in response to imagined darkness or brightness better reflects trial-by-trial fluctuations in imagery vividness within an individual than individual differences in imagery vividness as a personal trait.