Can Credible Information Reach Users? Experimental Evidence on Source Cue Effects on YouTube in Japan

Online political communication is increasingly video-centered, with platforms such as YouTube and TikTok playing a growing role in electoral processes worldwide, including in Japan.Although these platforms allow political actors to disseminate long-form content beyond the constraints of mass media, they also facilitate the spread of political information of uncertain reliability, making users ability to selectively access credible content essential for informed decision-making.Prior research suggests that source cues can serve as heuristics for credibility judgments and news selection in online, text-centered environments, yet evidence from Japan indicates that they do not function effectively on news aggregators.It therefore remains unclear whether source cues operate in video-based environments, where credible mainstream content and less reliable alternative media coexist, and under what conditions they may enable users to selectively access reliable information as video platforms increasingly shape public opinion.This study investigates whether source labels identifying mainstream mass media on