Confidence in auditory perceptual completion.

Previous studies examining confidence in perceptual completion in vision showed that observers can be unaware of missing sensory information and be even more confident in perceptually completed stimuli than veridical stimuli. In the current study, we aimed to investigate if auditory filling-in mechanisms would result in similar confidence biases. In two separate experiments, participants listened to continuous (uninterrupted) or discontinuous (interrupted) tones that were accompanied by noise. We examined confidence for continuity-discontinuity decisions by collecting confidence ratings (Experiment 1) and forced-choice confidence judgments (Experiment 2). Participants reported the interrupted sounds with masking noise more as uninterrupted, showing auditory filling-in. Confidence ratings in the first experiment followed response consistency. Forced-choice confidence judgments in the second experiment showed that participants were not able to distinguish the filled-in stimulus from a continuous stimulus with similar masking noise. Most importantly, there was no clear preference for a veridical compared to a perceptually completed stimulus. These results, extending findings from the visual modality, are the first to demonstrate that listeners are unaware of auditory filling-in and trust filled-in information almost as much as veridical information in the auditory sense.