Surprise-Induced Pupil Dilation Signals the Brain to Refresh and Learn Faster

Researchers tracked 63 adults as they predicted colors on a screen while their pupil size and brain activity were recorded. They found that surprise-triggered pupil dilation aligns with arousal signals in the locus coeruleus/norepinephrine system and EEG markers, helping the brain refresh context, adjust learning, and reduce perceptual bias when predictions are violated.