Half of our sample was exposed to civil reader comments and the other half to rude ones — though the actual content, length and intensity of the comments, which varied from being supportive of the new technology to being wary of the risks, were consistent across both groups. The only difference was that the rude ones contained epithets or curse words, as in: “If you don’t see the benefits of using nanotechnology in these kinds of products, you’re an idiot” and “You’re stupid if you’re not thinking of the risks for the fish and other plants and animals in water tainted with silver.”

The results were both surprising and disturbing. 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.