"Hearing as": Knowledge of Syntactic Structure Affects Event-Related Potential Components for Musical Expectation.

Harmonic expectation is an important mediator of musical experience. EEG research has identified event-related potential (ERP) components associated with expectation, including the early (right) anterior negativity (E(R)AN), which is theorized to index harmonic surprisal with reference to long-term memory of the statistical structure of music. However, the role of top-down influences on harmonic predictions remains underexplored. One specific influence concerns how a given harmony can be interpreted in different ways, depending on its syntactic role in a musical context. We present data from a novel paradigm that cues listeners to the syntactic structure of the stimuli (but not whether they contain improbable events). Our main result revealed larger E(R)AN amplitudes for improbable chords when listeners knew that additional context would follow a surprising harmony; P3a and P600 amplitudes were also larger in such cases. Using the theoretical framework of predictive coding, we propose that, in such cases, listeners assign higher precision to their predictions, leading to larger prediction errors as indexed by the E(R)AN, P3a, and P600 ERP components, and that prior context alone does not fully explain how unpredictable events are processed. Musical surprisal arises from a dynamic interplay between bottom-up cues and a listener's top-down anticipation within specific syntactic contexts.