Engaged listeners: shared neural processing of powerful political speeches

Abstract

Powerful speeches can captivate audiences, whereas weaker speeches fail to engage their listeners. What is happening in the brains of a captivated audience? Here, we assess audience-wide functional brain dynamics during listening to speeches of varying rhetorical quality. The speeches were given by German politicians and evaluated as rhetorically powerful or weak. Listening to each of the speeches induced similar neural response time courses, as measured by inter-subject correlation analysis, in widespread brain regions involved in spoken language processing. Crucially, alignment of the time course across listeners was stronger for rhetorically powerful speeches, especially for bilateral regions of the superior temporal gyri and medial prefrontal cortex. Thus, during powerful speeches, listeners as a group are more coupled to each other, suggesting that powerful speeches are more potent in taking control of the listeners' brain responses. Weaker speeches were processed more heterogeneously, although they still prompted substantially correlated responses. These patterns of coupled neural responses bear resemblance to metaphors of resonance, which are often invoked in discussions of speech impact, and contribute to the literature on auditory attention under natural circumstances. Overall, this approach opens up possibilities for research on the neural mechanisms mediating the reception of entertaining or persuasive messages.

Keywords: fMRI; inter-subject correlation; listening; rhetoric; speech.

Fig. 1

Inter-subject correlations of brain activity during listening to real-life political speeches. (A) ISC result maps for powerful speeches. (B) ISC for weak speeches.

Fig. 2

Differences in ISC between powerful and weak speeches. Significantly enhanced ISC was found in bilateral STG regions and mPFC, indicating that powerful speeches prompt more consistent neural responses across listeners.

Fig. 3

(A) ISC results for the control experiment with unintelligible reversed speeches. (A) ISC during listening to reversed powerful speeches. (B) ISC during listening to reversed weak speeches.

Fig. 4

Inter-subject correlations for powerful and weak speeches that were presented either normal (i.e. forward) or time-reversed, thus rendering the stimulus unintelligible. Bars represent mean ISC and error bars standard deviations. See text for further details.

Fig. 5

(A) Illustration of ISC results for powerful (orange) and weaker (blue) speeches (overlap in purple). (B) Neurosynth reverse inference maps for several linguistic features. For visualization purposes, data were mapped to the PALS-B12 surface atlas (Van Essen, 2005). (C) As in (A), but for the reversed speech control experiment.