Examining a conceptual framework of aggressive and humorous styles in science YouTube videos about climate change and vaccination.

The current study investigated how individuals process aggressive and humorous video messages communicating childhood vaccination and climate change. Employing psychological reactance, message discounting and expectancy violation, we built a theoretical model that explains the effects of communication styles on individuals' activism intentions. Two online experiments in the United States ( = 441 and  = 533) using self-created videos on the topics of childhood vaccination and climate change were conducted to examine this model. The results showed that both perceived aggressiveness and humorousness of the videos led to higher message discounting, which then resulted in stronger activism intentions. Perceived aggressiveness led to higher expectancy violation, while perceived humorousness led to lower expectancy violation, which negatively affected activism intentions. The role played by psychological reactance was inconsistent across the two contexts. The findings provide theoretical implications for understanding how individuals process aggressive and humorous communication styles, especially in relation to discussions on science issues.