Visual effects on the perception of persuasive speech

Abstract

Human communication is multimodal, e.g. it is composed of a set of verbal and non-verbal (visual) cues produced by the speaker with the aim to persuade the hearer’s thoughts and actions. However, the actual impact of the visual channel on the recipients’ impressions of persuasiveness is still not clear. The purpose of this investigation is to assess how the visual channel can impact on the perceived persuasiveness of public speeches. A set of 45 persuasive speeches delivered by a group of high school students in front of a real audience was assessed by a group of 15 raters who evaluated the persuasive effect of the speech on a 1 to 7 Likert scale. Crucially, they first assessed the isolated

audio-only version of the discourses (Audio-Only condition) and a week later the audio- visual recordings of the same speeches (Audio-Visual condition). A quantitative analysis

of the rater’s persuasive assessments revealed that AV presentations were perceived to be more persuasive than AO presentations of the same discourses. In order to assess why the visual presentation of the discourses triggered a more positive effect on hearers, a multimodal analysis was carried out for prosodic and non-verbal features of these discourses. The results showed that the speakers that obtained a mean improvement of 0.4 in their AV persuasiveness score used significantly more positive multimodal stance indicators (e.g., direct gaze at the audience, more communicative gestures, and more smiling faces) than the speakers that did not obtain an improvement. All in all, the present study shows that access to the visual channel tends to impact positively on the audience's perception of persuasive speech.