Jonah Berger and Katherine L. Milkman, professors at the University of Pennsylvania’s Wharton School of Business, similarly found that news stories were more likely to be shared if they elicited emotions like awe, anger and anxiety.

So when Mr. Trump says that Mexicans are rapists and killers, or that the government should register Muslims in the United States in a mandatory database system, people hit the share button. And as long as stories about Mr. Trump are receiving as many eyeballs as possible, it doesn’t really matter if people are reacting negatively to him. In fact, it probably helps his popularity.

That Mr. Trump is both volatile in nature and allergic to nuance is part of his viral success. Humans use mental shortcuts to process information quickly while conserving brain power. This means that we often don’t think critically about the information we’re receiving before sharing it with others.

Unsurprisingly, that can mean that things that are not true go viral. But lies, like fear, can maintain a powerful grasp on the human mind.

“Once we see something and accept it as true, it’s really, really hard to falsify the belief,” said Rosanna Guadagno, a social psychologist at the University of Texas at Dallas. “I’ve occasionally spread something that turned out to be false, and the sad thing is, I’m still trying to scrub that out of my memory as something I’ve accepted as real.”

And people with certain political leanings may be more predisposed to sharing. According to Bradley M. Okdie, a social psychologist at Ohio State University at Newark, conservatives are more likely to share a given piece of content than liberals are, especially if it provokes a negative emotion.

“Conservatives tend to be a lot more reactive to negative information and they also tend to be a lot more insular in nature, and they also tend to have less tolerance for ambiguity,” Professor Okdie said. “Conservatives would prefer a negative concrete statement to a slightly positive, uncertain statement.”