Comments can be bad for science. That's why, here at PopularScience.com, we're shutting them off.

[...]

...even a fractious minority wields enough power to skew a reader's perception of a story, recent research suggests. In one study led by University of Wisconsin-Madison professor Dominique Brossard, 1,183 Americans read a fake blog post on nanotechnology and revealed in survey questions how they felt about the subject (are they wary of the benefits or supportive?). Then, through a randomly assigned condition, they read either epithet- and insult-laden comments ("If you don't see the benefits of using nanotechnology in these kinds of products, you're an idiot" ) or civil comments. The results, as Brossard and coauthor Dietram A. Scheufele wrote in a New York Times op-ed:

Uncivil comments not only polarized readers, but they often changed a participant's interpretation of the news story itself.

In the civil group, those who initially did or did not support the technology — whom we identified with preliminary survey questions — continued to feel the same way after reading the comments. Those exposed to rude comments, however, ended up with a much more polarized understanding of the risks connected with the technology.

Simply including an ad hominem attack in a reader comment was enough to make study participants think the downside of the reported technology was greater than they'd previously thought.

Another, similarly designed study found that just firmly worded (but not uncivil) disagreements between commenters impacted readers' perception of science.

If you carry out those results to their logical end--commenters shape public opinion; public opinion shapes public policy; public policy shapes how and whether and what research gets funded--you start to see why we feel compelled to hit the "off" switch.

Comments on articles erode the public's trust in science.

The archenemy of scientific thinking is conversation, as in typical human conversational discourse, much of which is BS. I have become rather fed up with talking to people. Seriously, it is something of a problem. Fact is, folks are prone to getting pet opinions into their heads and thinking they’re true to the point of obstinacy, even when they have little or no idea of what they’re talking about in the first place. We all do it. It’s part of how the sloppy mind-generating piece of meat between our ears is prone to work. Humans may be the most rational beings on the planet these days—but that’s not saying much, considering that the next most rational are chimpanzees.

Gregory Paul on how conversations are prone to falshoods and equating opinions with facts.