“Well, what I think it’s doing is giving everyone a voice, right?” Mark Zuckerberg told ABC News in 2010, referring to the social network he founded. “So, back, you know, a few generations ago, people didn’t have a way to share information and express their opinions efficiently to a lot of people. But now they do. Right now, with social networks and other tools on the internet, all of these 500 million people have a way to say what they’re thinking and have their voice be heard.”

It’s a wonderful idea, and one that has fueled much of the excitement of the social-media age. But is it true? Is social media really fostering robust discussion and debate?

According to a new report from the Pew Research Center called “Social Media and the ‘Spiral of Silence,” the answer is no. In fact, it may be doing the opposite. Pew polled 1,801 Americans, asking them about their “opinions about the Snowden leaks, their willingness to talk about the revelations in various in-person and online settings, and their perceptions of the views of those around them in a variety of online and off-line contexts.” (Pew chose the Snowden story in part because polls have showed Americans are relatively evenly divided on it).

Despite the still-prevailing idealistic vision of social media as a platform for engaged citizenry and robust debate, the report notes that “people were less likely to discuss these issues on social media than they were in person.” Moreover, “if people thought their social media friends and followers disagreed with them, they were less likely to want to discuss the issues at all.”

Here are five important sentences from the report, and what they can tell us about how people debate hot-button issues online:

“The only settings where most people were not willing to discuss their opinion was on Facebook and Twitter.”

Only 42 percent of Facebook users and 41 percent of Twitter users said they’d be willing to discuss Snowden on those platforms, whereas well over half of respondents said they’d talk it over in community meetings, at family dinners, and in several other settings. In fact, 86 percent of Americans said they were willing to discuss Snowden in some offline venue. It appears people find Facebook and Twitter to be a lot less welcoming or engaging for these sorts of discussions.

“Someone who frequently uses the ‘like button’ on Facebook content contributed by other Facebook users (they use it a few times per day) is 1.88 times more likely to feel that their family members share their views, and they are 1.72 times more likely to feel they share the opinions of people in their Facebook network, when compared to those who do not use the like button.”

This is a fascinating finding, and the authors offer a few different explanations for it tied to the idea that Facebook networks tend to be like-minded, and the more engaged you are on Facebook, the more of this agreement you are likely to encounter, which could skew your perception of the extent to which the rest of the world (online and off) agrees with you.

They ignore, however, one important potential mechanism for how this might occur: The more you “like,” the more Facebook shapes the content you are presented via your news feed in a direction its algorithm thinks will increase your engagement. It may well be the case that if you’re liking a lot of stories on Snowden or any other specific news story, Facebook will detect that and serve you up more tasty red meat. (We already know, thanks to Mat Honan’s noble and masochistic experiment in Wired, that weird stuff happens when you click the “like” button indiscriminately.)

“Almost everyone in our sample who reported that they would be willing to discuss something on Twitter or Facebook also indicated that they would be willing to have a conversation on this topic in an offline setting.”

There was barely anyone — just 0.3 percent of those surveyed — who was willing to discuss Snowden online but not offline. One interpretation of this is that people’s online behavior mirrors, to a certain extent, who they are offline: If you’re rant-y and opinionated at parties, you’re rant-y and opinionated on Facebook. Or perhaps social media has emboldened a lot of otherwise quiet people to speak up, and this confidence has extended to their offline interactions. (Purely anecdotally, I find there’s a pretty strong correlation between who is opinionated on my Facebook feed and who is outwardly opinionated in real life.)

One possibility that these numbers rule out, though, is that Twitter and Facebook are at the moment giving a major voice to people who would be unlikely to participate in political debates offline. If that were the case, you’d see much less overlap between the online and offline discussion-havers.

“When social media followers disagree, people are more likely to self-censor offline.”

In many cases, the report notes, social-media use correlated with a lower overall likelihood of joining the conversation about Snowden. If social media increases exposure to differing opinions, the authors write, “this might increase the likelihood that people will choose to withhold their opinion because they know more about the people who will object to it,” and some of the data supports that idea: Facebook members with typical usage rates were 47 percent less likely to want to discuss Snowden with friends at a restaurant, for example, but only 26 percent less likely to talk about Snowden with friends “[i]f they feel that people in their Facebook network agree with their opinion.”

This makes some intuitive sense. If you’ve just emerged from a bruising Facebook comment thread about Snowden, it’s easy to imagine feeling your energy a bit more sapped when that subject comes up at dinner than you would if everyone on your feed agrees.

“[O]n Facebook, women are as likely as men to feel comfortable discussing an important political issue.”

Pew’s report isn’t all bad news. It notes that on Facebook, both women and people with less formal education appeared more willing to discuss Snowden than they did in other settings — most of which tend to be dominated by the voices of men, and particularly well-educated ones. At least a glimmer of that idealistic social-media world is on display here.

***

This report has a lot of moving parts, but most of them point in the same direction: Facebook and Twitter have not done a particularly good job incubating productive political discussion, at least when it comes to one of the most important, hot-button issues of the last few years. But the report definitely shouldn’t be seen as an indictment of social media writ large; rather, this may be more about the limitations and personalities of these two particular platforms than about the wider concept of social-media-fueled political debate.

Pew only scratches the surface of why Facebook and Twitter might tamp down political discussion, for example, and to the extent the researchers speculate about this, they may be downplaying the issues of tone and civility. It could be that people drop out of conversations not when they sense others disagree with them, but when that disagreement is delivered in an overly antagonistic, vehement way. What would the numbers in Pew’s report look like if Facebook and Twitter didn’t lend themselves so easily to outburst and groupthink and snark? Is it possible on popular social-media platforms to build that tone down rather than to exacerbate these all-too-human tendencies?

Finally, it’s important to keep in mind that there’s some incentive misalignment here. Some of us would love better outlets for intelligent online discussion, but neither Facebook nor Twitter has ever claimed this to be among their top priorities. Rather, they want clicks and shares and retweets. Lofty quotes notwithstanding, what are the odds that closed-door meetings of higher-ups in Menlo Park and San Francisco ever involve into discussions about what these companies can do to promote robust and intelligent political dialogue?

People may be asking too much of these platforms — if they want social media that reflects their highest ideals for political debate and inclusion, it could be time to build something new.

Lori Keong contributed research.