A platform penalty for news? How social media context can alter information credibility online

Growing concern about dubious information online threatens the credibility of legitimate news. We examine two possible mechanisms for this effect on social media. First, people might view all news on social media as less credible. Second, questionable information elsewhere in a news feed might discredit legitimate news coverage. Findings from a preregistered experiment confirm that people see information on Facebook as less credible than identical information on news websites, though the effect is small, suggesting that observational data overstates this platform penalty. Prior exposure to low (versus high) credibility information on Facebook also reduces engagement with a target article, but not its perceived credibility. However, exploratory analyses show that the effects of prior exposure to low credibility information vary depending on the plausibility of the target article, decreasing the credibility of a less plausible article (a spillover effect) but increasing the credibility of a more plausible one (a contrast effect).