It’s the person who shares a story, not the source of the news, that matters in gaining readers’ trust on social media, new research found.

Media Insight Project, a collaboration between the American Press Institute and The Associated Press-NORC Center for Public Affairs Research, interviewed more than 1,400 US adults from November to December 2016 to see how much faith people placed in news sources.

Each participant was shown the same article—”Don’t let the scale fool you: Why you could still be at risk for diabetes”—in a news feed that resembled that of Facebook. But the person who shared it and the original reporting source shown was different for each person.

Half of the participants were randomly shown a sharer they previously said they trusted—one of eight public figures who often share information about health including Oprah, Dr. Oz, and the US surgeon general—and the other half were shown a sharer they didn’t trust. (The study did not look at the impact of stories shared by respected friends, colleagues, or family members on social media.) Half the sample was also randomly shown the article was published by the Associated Press, while the other half was shown a made-up news provider, DailyNewsReview.com.

They were then asked to describe the piece of news. Half the respondents said the story got the facts right when it was shared by a public figure they trusted, compared to 35% who said the same when they didn’t trust the sharer. And the pattern held true for those who said the story was well-reported.

The participants were also more likely to share the article, follow the person who shared it, or otherwise engage with the post when they got it from an influencer they trusted.

The news source that reported the story, meanwhile, didn’t have much of an affect on whether the respondents believed the story to be true.

Other studies, including a 2016 report from the Media Insight Project, found that Americans in general were highly skeptical of news they found on social media and leaned on original reporting sources to decide how much stock to place in the news. But, as this study shows, the person who shares a story is much more influential than people realize. A highly trusted or distrusted sharer could sway a reader’s opinion of a story more than the news outlet that published it.

“All of this suggests that a news organization’s credibility both as a brand and for individual stories is significantly affected by what kinds of people are sharing it on social media sites such as Facebook,” said Media Insights Project, in the latest report. “The sharers act as unofficial ambassadors for the brand, and the sharers’ credibility can influence readers’ opinions about the reporting source.”

This is especially important now as more and more US readers are finding their news on social media. Facebook recently added new tools to help users spot fake news more easily, and other social networks have similarly taken steps to curb false reports on their platforms.

Overall, about half of the participants in the study could recall who shared the post in the study, while only two in 10 participants could remember the actual source of the news. The participants were, however, turned off by news organizations they inherently did not trust, and were less likely to describe those stories in a positive light.