‘Groove’ can be understood as the (pleasurable) urge to move to music. Predictive accounts of music listening posit that groove reflects an embodied suppression of prediction errors (i.e., active inference) arising from moderate levels of complexity. Here, there are frequent prediction errors that challenge internal models of the rhythmic structure but not to the point of failure, compelling us to reinforce these models with our own movements. Thus, it stands to reason that actual movement would increase feelings of groove, however this central assertion had not yet been directly tested. We recorded pupil diameters (as an index of musical effort) while participants either synchronously tapped their foot or just listened to short clips from real music that varied in ‘pulse entropy’. Immediately after each excerpt, participants rated their experience of groove. In accordance with predictive coding, excerpts were rated higher in groove and evoked greater pupil dilations with sensorimotor feedback from actively synchronizing to the music compared to listening. We also confirmed that the inverted U-relationship between rhythmic complexity and groove extended beyond artificial stimuli to more ecological music. Moreover, subjects tapped softer to more complex rhythms where their movements were also less precise, and thus less helpful for reinforcing internal rhythmic structures. Overall, these findings can be interpreted as supportive of the predictive coding of music model, at least in the context of groove.

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