What influences young people’s assessments of source credibility and persuasiveness? Traditional accounts of political socialization do not consider this question, which is critically important in our current political context. The proliferation of social media and rising political polarization have changed radically the landscape of political information transmission (Settle 2018, Vosoughi et al., 2018; Shao et al., 2017) and the interaction of these changes has fostered an environment where misinformation widely circulates and people distrust both traditional media and the government. We know little about the effects of these changes in the media landscape on the process of political socialization, despite an expectation that the information young people encounter on social media may be particularly relevant to their political development. Young people do not yet have firm political attachments or orientations. Because there is considerable ideological heterogeneity on social media, they are exposed to more diverse messaging than they may have been in traditional media environments. However, their weaker partisan attachment leaves them without a party heuristic to parse quickly through the information they encounter. What cues do young people take in the absence of strong party cues to assess political arguments? In order to answer these questions, we will conduct two studies: a study fielded on a sample of American teenagers and an identical study fielded to a nationally representative sample of American adults.