Music chills: The eye pupil as a mirror to music’s soul

•Music chills are bodily responses corresponding to peak emotional experiences.•Chills are reported more frequently for self-selected songs than songs selected by others.•Pupil size was larger within specific time-windows around the chill events.•Pupil size increase both in an active (key response) and passive (simply listening) conditions.•A neuromodulatory role of the central norepinephrine system is implicated in this phenomenon. This study evaluated whether music-induced aesthetic “chill” responses, which typically correspond to peak emotional experiences, can be objectively monitored by degree of pupillary dilation. Participants listened to self-chosen songs versus control songs chosen by other participants. The experiment included an active condition where participants made key presses to indicate when experiencing chills and a passive condition (without key presses). Chills were reported more frequently for self-selected songs than control songs. Pupil diameter was concurrently measured by an eye-tracker while participants listened to each of the songs. Pupil size was larger within specific time-windows around the chill events, as monitored by key responses, than in comparison to pupil size observed during ‘passive’ song listening. In addition, there was a clear relationship between pupil diameter within the chills-related time-windows during both active and passive conditions, thus ruling out the possibility that chills-related pupil dilations were an artifact of making a manual response. These findings strongly suggest that music chills can be visible in the moment-to-moment changes in the size of pupillary responses and that a neuromodulatory role of the central norepinephrine system is thereby implicated in this phenomenon.