President Donald Trump made roughly 500 false statements in the first 200 days of his presidency, according to the Toronto Star’s Daniel Dale. That’s an impressive amount of misinformation, and it’s turned news networks into full-time fact-checking organizations, with journalists frequently having to pause their regular programming to debunk Trump’s latest tweet or public statement.

But all that fact-checking hasn’t stopped many Trump supporters from believing misinformation to be true. Two-thirds of Republican voters still believe millions of people voted illegally during the election. A majority of Trump supporters think Obama spied on him during the campaign, and almost half still think Trump won the popular vote.

How is that possible? Why isn’t fact-checking enough to convince people to abandon inaccurate political beliefs?

Brendan Nyhan, a political scientist who’s spent years studying the effects of fact-checking, says the durability of those false beliefs isn’t unique to Trump supporters — it represents a basic problem with human psychology.

“We’d all like to think we’re dispassionate,” Nyhan explains, “but as human beings we’re all skeptical of information that seems to contradict some existing value or belief or attitude that we have. And so we can be unduly skeptical of that information that is unwelcome.”

That skepticism is amplified when it comes to politics. When a fact-checker attempts to debunk a widely touted belief held by a particular political party, members and supporters of that party are likely to perceive the fact-check as challenging an important part of their identity, making them more likely to reject corrective information.

That aversion to fact-checking isn’t just a problem for Trump supporters — it affects everyone. And it should inform the way news networks go about trying to correct misinformation coming out of the White House.

Watch the video above to understand why our brains and journalistic conventions make it so hard for us to correct misinformation.