It may not be surprising that people tend to be skeptical about facts that challenge their point of view. What is surprising, though, is that many people's opinions become more entrenched when they're presented with facts that disprove them.

It's called the backfire effect. Debunking falsehoods often strengthens the conviction that they're true — for people all across the political spectrum.

Brendan Nyhan is a pioneer in studying the backfire effect. He's an assistant professor at Dartmouth College, and a co-author of "All The President's Spin: George W. Bush, The Media and The Truth."

Giving people factual information isn't as convincing as people often think. - Brendan Nyhan

"I come to this subject through painful experience — I used to do fact-checking myself. I was one of the founders of an online website that was a forerunner to some of the fact-checking websites now," says Nyhan. "It was striking how difficult it was to change people's minds, even among the people who would seek out a fact-checking website. They very often resisted our conclusions when it ran counter to their own political dispositions."

PolitiFact, the fact-checking website run by the Tampa Bay Times, has put 144 statements by Trump to the truthfulness test and found that 79 per cent were mostly false, false or pants-on-fire false. Nyhan says he doesn't believe all of Trump's support is connected to the backfire effect, but its existence makes it more difficult for journalists covering the presidential election to do their jobs. (Note: since this interview was recorded, PolitiFact's ratings have changed. As of June 17, 2016, they had examined 160 statements by Trump; 76 per cent were judged mostly false, false, or pants-on-fire false.)

"I think it's fair to say that he's exploiting the willingness of his supporters to side with him even when he's blatantly misrepresenting the facts over and over again," he says.

"And it creates a real dilemma for the journalists who cover him: how often do they fact-check him when the folks who don't like Trump already think he's a liar, and the folks who do either don't believe the fact-check or don't care?"

Click the button above to hear Michael's conversation with Brendan Nyhan.