Republican presidential frontrunner Donald Trump continues to insist he saw thousands of people on TV in Jersey City celebrating right after the 9/11 terror attacks, even though there is absolutely no evidence to support the claim, several officials are refuting it.

But he's not alone — hundreds of people have written in to New Jersey 101.5's Facebook page or called the station insisting they saw the same (most recently, here). Some say it was a handful of celebrants, not thousands. Some say it was in other cities.

But among those hundreds, many are dead-sure they saw it on the news — even though fact-check stories by PolitiFact and the The Washington Post, among others, can't find any sign such footage exists. So far, no footage has surfaced on social media, in mainstream news, on political blogs or in alternative media. No network has pointed to any archive of its own saying such footage exists. Only unconfirmed reports or descriptions of rumors have been found in news articles from the time.

So what is going on here?

“Memories are not facts, memories are constructions, and often-times people recall things that are false,” according to Rutgers University sociology professor Deborah Carr.

She points out sometimes people can’t differentiate fact from fiction, but in other cases “memories are storytelling, people try to conjure up memories and stories that support the tale that they’re trying to tell. Sometimes people will either conjure up a memory or construct a memory so that they can support some kind of identity they’re trying to assert.”

She says a great example of this is the most famous rock concert in history.

“The number of baby boomers who say they attended Woodstock is way high higher than the number who were actually there,” says Carr, “the number of people who recall voting for JFK is much higher than the number of people that actually did – so sometimes if someone feels they want to be part of a movement, no matter what it is.”

She points out this happens all over the world and across time.

“We know that memory, regardless of who you are or where you are is not perfect,” she said. “If you think about your childhood memories, can you really tell for a fact that something really happened, or perhaps it was a comical tale your parents told that may not be true but it enters your consciousness?”

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Paterson Police Director Jerry Speziale — who is emphatic in his assertion to New Jersey 101.5 that no groups of Muslims or anyone else were seen celebrating in his city’s streets, despite similar rumors that have persisted for years — has his own theory of why the impression persists:

“The media was going form the World Trade Center, then to the Middle East, then to the Muslim communities in NJ,” Speziale said. “Could one make the assumption and say, ‘I just saw someone burning flags’ and think it was America? Yes, I guess.”

Carr said it’s impossible to tell if Donald Trump believes what he is saying, but there have been multiple indications of him saying things that are not substantiated by any fact.

Patrick Murray, director of the Monmouth University Polling Institute, said “one of the things Trump is tapping into with his supporters is an underlying sense that he’s speaking the truth, even if the facts aren’t correct.”

He said pollsters see this kind of false memory situation all the time when they ask people to recall their own experiences.

“(It happens) whether it’s who they voted for or whether it’s what they ate for dinner last night. In fact I once did a poll asking what they ate for dinner over the past week and people could not remember what they ate,” Murray said.

He said another example of this is polling about an election might be accurate right up until the election, but then immediately after the election “when we ask people who they voted for, suddenly we get an over-reporting of the winner. It’s not clear if they mis-remembered who they voted for, or if they simply wanted to remember what happened in a different way.”

Murray adds it’s interesting that Trump is not trying to point to specific facts to convince anybody that there were thousands of people celebrating 9/11 in Jersey City.

“It’s the idea that he’s tapping into the sense that, particularly for his supporters, that this is something that could have actually happened and therefore it’s just as real as if the facts were correct,” he says. "Usually candidates are a little worried about getting caught in factual errors, what’s so interesting about Donald Trump is that he simply is not afraid of that. For him the facts simply don’t matter. It’s not that he’s trying to lie, it’s just that he’s simply saying that the fact itself is not relevant to the purpose of my campaign.”

New Jersey’s governor at the time has said he doesn’t remember any such celebrations and current Gov. Chris Christie doesn’t remember any. The celebrations have been outright denied by Jersey City’s mayor, as well as by the police director of nearby Paterson.