Delivery and Attitude Modulate Shared Neural Processing of Speech Through Distinct Frequency Channels.

Listeners' brains align when they attend to the same speech, but what determines how strongly they align is not well understood. We asked whether that alignment tracks the communicative relation between a listener and a message, manipulating it from the speaker's side and from the listener's, and bounding the account with a manipulation that alters the social setting while leaving the relation intact. In two magnetoencephalography experiments, we measured inter-subject correlation of band-limited envelopes, which resolves shared processing by frequency rather than treating it as a single quantity. In Study 1, 40 listeners watched the same actor deliver the same speech charismatically and non-charismatically, so that content and identity were held constant. Charismatic delivery raised correlation most strongly in the beta band, and after regression of the acoustic and visual features, the surviving effect was concentrated in right perisylvian cortex. In Study 2, listeners read a favorable or unfavorable description of a speaker they had never encountered and watched a second speaker either with or without a minimal cue that an audience was present. A newly formed attitude raised correlation in alpha and theta within the same right perisylvian region, whereas the audience cue, which left both the message and the listener's disposition unchanged, produced no detectable change in any band. Correlation also proved partly dispositional: how strongly a listener synchronized on one task predicted their synchrony on the other, specifically in alpha and independently of personality. Delivery and attitude thus converge on a common substrate for the speaker's expressive signal, reaching it through separate frequency channels.