Boston — Scientists have a hard enough time getting people to understand what they’re talking about.

Their thoughts can be complicated. Their sentences can be laden with jargon. And their conclusions can offend political or religious sensibilities.

And now, to make things worse, readers have an immediate forum to talk back. And when some readers post uncivil comments at the bottom of online articles, that alone can raise doubts about the underlying science, a new study has found. Or at least reinforce those doubts.

The study, outlined on Thursday at the annual meeting of the American Association for the Advancement of Science, involved a survey of 2,338 Americans asked to read an article that discussed the risks of nanotechnology, which involves engineering materials at the atomic scale.

Of participants who had already expressed wariness toward the technology, those who read the sample article—with politely written comments at the bottom—came out almost evenly split. Nearly 43 percent said they saw low risks in the technology, and 46 percent said they considered the risks high.

But with the same article and comments that expressed the same reactions in a rude manner, the split among readers widened, with 32 percent seeing a low risk and 52 percent a high risk.

“The only thing that made a difference was the tone of the comments that followed the story,” said a co-author of the study, Dominique Brossard, a professor of life-science communication at the University of Wisconsin at Madison. The study found “a polarization effect of those rude comments,” Ms. Brossard said.

The study, conducted by researchers at Wisconsin and George Mason University, will be published in a coming issue of the Journal of Computer-Mediated Communication. It was presented at the AAAS conference during a daylong examination of how scientists communicate their work, especially online.

Ms. Brossard described her findings at a session moderated by Carl Zimmer, an author and lecturer at Yale University who specializes in science and the environment. Mr. Zimmer said he handles rude comments on his own blog by warning the writer once, then blocking the writer’s access if the rudeness continues.

That tactic should be widely adopted, Ms. Brossard said, given that social norms that have evolved over the millennia for people speaking with one another in public have not yet made a similar evolution online.

Scientists and science writers need to realize the power they have to control their online environments, said Janet D. Stemwedel, an associate professor of philosophy at San Jose State University who studies ethical issues in science.

“It’s useful in reassuring bloggers who have been moderating comments that what they are doing is not just permissible but also reasonable,” said Ms. Stemwedel, who was not at the AAAS conference.

The annual meeting of the AAAS, which describes itself as the world’s largest general scientific society, runs from Thursday through Monday.