Motivated by the goal of designing interventions for softening polarized opinions on the Web, and building on results from psychology, we hypothesized that people would be moved more easily towards opposing opinions when the latter were voiced by a celebrity they like, rather than by a celebrity they dislike. We tested this hypothesis in a survey-based randomized controlled trial in which we exposed respondents to opinions that were randomly assigned to one of four spokespersons each: a disagreeing but liked celebrity, a disagreeing and disliked celebrity, a disagreeing expert, and an agreeing but disliked celebrity. After the treatment, we measured changes in the respondents' opinions, empathy towards the spokespersons, and use of affective language.

Unlike hypothesized, no softening of opinions was observed regardless of the respondents' attitudes towards the celebrity. Instead, we found strong evidence of a hardening of pre-treatment opinions when a disagreeing opinion was attributed to an expert or when an agreeing opinion was attributed to a disliked celebrity. We also observed a pronounced reduction in empathy for disagreeing spokespersons, indicating a punitive response. The only celebrity for whom, on average, empathy remained unchanged was the one who agreed, even though they were disliked.

Our results could be explained as a reaction to violated expectations towards experts and as a perceived breach of trust by liked celebrities. They confirm that naive strategies at mediation may not yield intended results, and how difficult it is to depolarize-and how easy it is to further polarize or provoke emotional responses.