If you spend enough time on social networks like Facebook and Twitter, it’s easy to convince yourself that both are just giant echo chambers where users with specific political views talk to each other and different viewpoints are ignored.
But new research suggests that’s not always the case.
According to a recent study by the Pew Research Center, a non-partisan think tank located in Washington, D.C., being exposed to differing views via social media can actually cause people to rethink how they view a political issue. Not always, but sometimes.
The Pew study found that 20% of those surveyed said that they had modified their stance on a social or political issue because of something they saw on social media, and 17% said that viewpoints they encountered through social media had changed their views about a specific candidate.
Democrats were a little more likely than Republicans to say they had modified their views as a result of something they saw on social media, the study said.
Get Data Sheet, Fortune’s technology newsletter.
The Pew Center’s researchers didn’t just ask this question. They also asked respondents to give them examples of specific times that such a change had occurred and why. According to their report, in most cases the viewpoints these users were exposed to changed their stance in a negative way.
For example, respondents who admitted that they had changed their minds about Democratic presidential nominee Hillary Clinton were more than three times as likely to say that their opinions had grown more negative than more positive. Said one survey taker:
I thought Donald Trump was leaning one way on an issue and a friend posted something that was opposite of what I believe. This caused me to think less of him than I once I did.
Those who mentioned that they had changed their opinion of Donald Trump based on social media posts, meanwhile, were almost five times more likely to have changed it in a negative direction rather than a positive one. Almost 20% said it became more negative, while just 4% said it became more positive.
Although the election and the current candidates were a big source of changes, the Pew Center also said that some respondents changed their minds about broader social issues as well.
Donald Trump outsmarted Hillary when it comes to earned media. Watch:
Almost 14% of those who said they had changed their views on a social question mentioned racial issues such as police brutality and the Black Lives Matter movement. Several users who said they were initially skeptical of such issues reported that they had changed their minds. Said one:
I’m white. Initially, I saw nothing wrong with saying ‘All lives matter’ – because all lives do matter. Through social media I’ve seen many explanations of why that statement is actually dismissive of the current problem of black lives seeming to matter less than others.
While these kinds of cases are encouraging, the researchers at Pew noted that the vast majority of social media users—approximately 82%—said they have never changed their views about a candidate based on what they saw someone else say, and 79% have never changed their views on a social issue.