Conscious processing of auditory regularities induces a pupil dilation.
Scientific reports October 4, 2018 Marion Quirins, Clémence Marois, Melanie Valente et al.
Pupil dilation is a reliable marker of conscious mental effort. In healthy volunteers, consciously detected violations of global auditory patterns triggered pupil dilation, whether participants actively counted or passively listened. This effect appeared at both group and individual levels. Unreported violations of global patterns, and local violations that do not require conscious awareness, produced no pupil dilation. The results were replicated with phonemes. Pupil dilation appears to be a somatic marker of conscious access in the auditory modality, offering a way to probe conscious processing without interrupting a person's stream of thought.