Americans have been self-censoring their discussions about state surveillance in the wake of Edward Snowden’s revelations in 2013, researchers have found.

Approximately 86% of adults were “very” or “somewhat” willing to discuss the findings in person with family, friends or work colleagues or at public meetings, yet only 43% said they would discuss the issues on Facebook.

The Pew Research Centre surveyed 1,801 US adults in August and September 2013, and also found that only 41% of people would be willing to discuss surveillance on Twitter which is a more visible, public medium than Facebook.

Pew’s report, which was published on Tuesday, warns of a “spiral of silence” capable of spreading from the online to the offline world, especially for people who think most of their social networking contacts disagree with their views on a particular topic:

“The typical Facebook user – someone who logs onto the site a few times per day – is half as likely to be willing to have a discussion about the Snowden-NSA issues at a physical public meeting as a non-Facebook user.

Similarly, the typical Twitter user – someone who uses the site a few times per day – is 0.24 times less likely to be willing to share their opinions in the workplace as an internet user who does not use Twitter.”

The report also notes that of the 14% of Americans who were unwilling to discuss the Snowden revelations offline, just 0.3% said they would be willing to join conversations on the topic on social networks instead.

“It has been well documented since before the internet that a “spiral of silence” descends when people think their opinions are in the minority when compared to those around them – they don’t want to speak out if they think they hold unpopular views,” said Prof Keith Hampton, one of the report’s co-authors.

“This kind of self-censoring can mean that important information is never shared. Some had hoped that social media might provide new outlets that encourage more discussion and the exchange of a wider range of opinions. But we see the opposite – a spiral of silence exists online, too.”

It is no surprise that both online and offline, Americans were more willing to share their views on Snowden and online surveillance if they thought that their audience agreed with them.

However, the report suggests that Facebook and Twitter users were less likely to join offline conversations if they felt that their views were out of step with their online friends and followers.

“This suggests a spiral of silence might spill over from online contexts to in-person contexts, though our data cannot definitively demonstrate this causation,” warns the report.

Pew’s survey did not ask people why they did not feel comfortable discussing Snowden, so getting to the bottom of the spiral of silence in this particular case is difficult. Its report does offer some suggestions:

“The traditional view of the spiral of silence is that people choose not to speak out for fear of isolation. Other Pew Internet research has found that it is common for social media users to be mistaken about their friends’ beliefs and to be surprised once they discover their friends’ actual views via social media.

Thus, it might be the case that people do not want to disclose their minority views for fear of disappointing their friends, getting into fruitless arguments, or losing them entirely. Some people may prefer not to share their views on social media because their posts persist and can be found later—perhaps by prospective employers or others with high status.”

Reports that numerous large internet companies’ security had been compromised by the NSA might seem to be the obvious explanation for Facebook and Twitter users’ reluctance to discuss the leaks on those social networks.

Pew’s report warns that at the time its survey was conducted – between 7 August and 16 September 2013 – the Snowden revelations had focused on the NSA’s collection of metadata relating to people’s phone and internet usage, but had not yet extended to subsequent details of surveillance of online discussions.

“In reaction to these additional revelations, people may have adjusted their use of social media and their willingness to discuss a range of topics, including public issues such as government surveillance,” suggests the report.

“However, given the limited extent of the information leaked by Snowden at the time the survey was fielded, it seems unlikely that the average American had extensively altered their willingness to discuss political issues.”

The Guardian first reported the existence of the NSA’s Prism program on 6 June 2013, including internal documents claiming that the agency had “direct access” to data held by Facebook, Google and Apple, although Twitter was not mentioned.

Pew’s report also provides an insight into how Americans got their information on the Snowden story, with 58% saying they got at least some details from TV and radio programmes.

Pew found that 34% cited online sources other than social media; 31% said friends and family; 19% said print newspaper; 15% cited Facebook and just 3% said Twitter.

Meanwhile, 26% of people surveyed were very interested in the NSA surveillance story at the time of the survey, while 34% were somewhat interested, 19% “not too interested” and 20% not interested at all.

When asked whether they favoured or opposed “a government program to collect nearly all communications in the US as part of anti-terrorism efforts”, 13% said they were strongly in favour, 24% somewhat in favour, 22% somewhat opposed and 30% strongly opposed.

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