A new study from Wayne State University’s Elizabeth Stoycheff provides strong evidence that the growing perception of government surveillance of Internet communication is having a serious deleterious impact on the willingness of individuals to express “controversial” views online.

The study found that subjects primed before questioning with information giving them the impression the government is watching what they say are much less likely to disclose political views, and are reluctant to reveal any non-mainstream opinions they hold.

The study showed that people not afraid of surveillance are actually slightly more likely to express controversial opinions in an environment “hostile” to those views, but that their willingness falls precipitously if they think the government is watching.

Stoycheff concluded that mass surveillance is silencing minority views, saying policymakers need to think more carefully about the impact their “national security precautions” have on free speech.