Blame the opponent! Effects of multimodal discrediting moves in public debates.

In political persuasion, the persuader, besides bearing logical arguments and triggering emotions, must present one’s own image (one’s ethos) of a credible and reliable person, by enhancing three dimensions of it: competence, benevolence, and dominance. In a parallel way, she/he may cast discredit on the opponent by criti- cizing, accusing or insulting, on the same three dimensions. The work provides a description and a typology of multi- modal discrediting moves focusing on the discrediter’s multimodal behavior. Based on an Italian corpus of polit- ical debates, the analysis points out which facial expres- sions, gaze behavior, gestures, postures, and prosodic features are used to convey discredit concerning the three target features of competence, benevolence, and domi- nance. Finally, an experimental study is presented assess- ing the effects of the different types of discrediting moves on potential electors. Results show that casting discredit on the other’s competence while also performing gestures, and casting discredit on the other’s dominance without ges- turing, makes arguments more shareable and convincing.