Ben Carson in September. (Chris Keane/Reuters)

Since last week, sometime Republican presidential front-runner Ben Carson has been battling stories about his stories of his dark past. In a 1990 memoir and in many speeches since, he claimed he was a violent youth; that he had tried to hit his mother with a hammer; that he had tried to stab a classmate at 14; that he had punched another with a lock in his hand. The problem: CNN went looking for people who could confirm these tales of schoolyard fisticuffs or worse, and the network couldn’t find any.

“We went out to find these people in Detroit,” CNN’s Maeve Reston said. “We went through the yearbooks. We called many of his classmates. We found his close friends through every period of his life. And the person that he describes in these anecdotes on the campaign trail as leading up to this religious epiphany that he had cannot remember any episodes of violence involving Dr. Carson.”

It turned out Carson had used pseudonyms for his victims and, though he said he was still in touch with at least one of them, wouldn’t make them available. It was a question of privacy, he said — even after a flawed Politico story about Carson’s alleged “full scholarship” to West Point raised more questions about his memory. Over the weekend, Carson suggested that the media find another tale to tell.

After Republican presidential candidate Ben Carson's past came under question, Carson said the media is "getting desperate" at a news conference in Florida on Friday, Nov. 6. (Reuters)

“It’s time to really move on,” he said on “Meet the Press.” “It’s not time to spend every single day talking about something that happened 50 years ago.”

[Why won’t Politico slap a correction on its Carson story?]

But Carson’s memory problems are not unique to the pediatric neurosurgeon. They are shared by at least one of his rivals for the presidential nomination; they are shared by countless memoirists and witnesses to crimes; indeed, they are shared by anyone who remembers anything. For study after study shows that our memories deceive us, even when we insist they do not.

“We don’t really remember the original; we remember the revised version,” Daniela Schiller, a Mount Sinai School of Medicine neuroscientist, explained in 2013. “… Every day we create false memories.”

This is not news to researchers. Though we may think of the act of remembering as the equivalent of pressing play on a some kind of internal YouTube, pioneering memory researcher Elizabeth Loftus said it was “more akin to putting puzzle pieces together than retrieving a video recording.” In 1974, for example, she showed how leading questions can affect memories of car collisions.

“When the experimenter asks the subject, ‘About how fast were the cars going when they smashed into each other?’ he is effectively labeling the accident a smash,” she and a co-author wrote. “… It is natural to conclude that the label, smash, causes a shift in the memory representation of the accident in the direction of being more similar to a representation suggested by the verbal label.”

In other words: “You can influence eyewitness testimony just by investigating an event,” said Schiller.

Defense attorneys, of course, must make the case that eyewitnesses misremember traumatic events. And science is on their side.

“Through such scientific research, we have learned that many factors influence the visual perceptual experience: dim illumination and brief viewing times, large viewing distances, duress, elevated emotions, and the presence of a visually distracting element such as a gun or a knife,” the National Research Council wrote last year. “Gaps in sensory input are filled by expectations that are based on prior experiences with the world. Prior experiences are capable of biasing the visual perceptual experience and reinforcing an individual’s conception of what was seen.”

Even one of the nation’s most august founding fathers, James Madison, was not immune to such bias. His copious notes of the Constitutional Convention of 1787 used by scholars and the courts to interpret the origin and meaning of the nation’s founding document, are considered only semi-reliable, as he altered them through the years before they were published posthumously. They were revised “as he changed his understanding about the Convention,” wrote Mary Sarah Bilder, a Boston College Law Professor and author of “Madison’s Hand: Revising the Constitutional Convention.”

As he edited the original notes, “he converted himself into a different Madison. In the original notes, Madison was annoyed and frustrated. Slowly by altering a word here, a phrase there, he became a moderate, dispassionate observer and intellectual founder of the Constitution.”

“Research illustrates that the human mind is not like a tape recorder; we neither record events exactly as we see them, nor recall them like a tape that has been rewound,” the Innocence Project, which defends people it believes have been wrongly convicted, wrote on its Web site. “In eyewitness identifications, witness memory is impacted by a variety of factors that occur from the time of the crime onwards, and their memories can be easily contaminated.”

To see this in action outside of a criminal court, one need look no further than Carson’s companion on many a debate stage: Donald Trump. In an review of Trump’s recently published book “Crippled America: How to Make America Great Again,” Trump biographer Michael D’Antonio wrote of the candidate’s shortcomings when it comes to self-evaluation.

“Accuracy is not a strong feature of this book, even when Trump talks about himself, which he does almost continually,” D’Antonio wrote. He proceeded to dissect elements of Trump’s origin story:

In his telling, he started his professional life at “a relatively small real estate company based in Brooklyn.” In fact the Trump organization built by his father, Fred, was one of the biggest in New York City — it was based in Brooklyn, and the Trump operation counted about 15,000 apartments in that borough and in Queens. By the time Donald undertook his first big project, the Trump holdings were worth an estimated $200 million, which made his dad one of the richest men in the country.

And about that first project. In Donald Trump’s retelling of the story of the renovation of the old Commodore Hotel it was “on the verge of becoming a welfare hotel.” This is not the case. The hotel was in business until the very end, and its owners were too concerned about maintaining its value to consider what Trump suggests. Also, Trump repeats the claim that he received little help from his father, other than a $1 million loan. The truth is that Fred Trump guaranteed the project himself, and put both his financial and political credibility on the line so his son could succeed.

Still, Trump and Carson’s somewhat jumbled memories in their books are not wholesale fabrications of a fabulist like James Frey, the author of “A Million Little Pieces,” an autobiographical book promoted by Ophrah Winfrey until it was exposed as a million little lies. Instead, they may be embellishments or distortions of the Brian Williams variety: exaggerations, differences in interpretation or emphasis that arise as decades go by and, in the heat of a presidential campaign, are again refashioned to make their authors look good. Do the candidates deserve to be raked over the coals for puffery? That’s up to voters. But Trump’s job in his new book, after all, is not to write a fair-minded self-assessment. It is to win a presidential election.

Indeed, in “The Art of the Deal” (1987), Trump seemed less his own biographer than his own carnival barker.

“I play to people’s fantasies,” Trump wrote. “… It’s an innocent form of exaggeration — and a very effective form of promotion.”

More from Morning Mix

Scientist falsified data for cancer research once described as ‘holy grail,’ feds say

Starbucks ‘removed Christmas from their cups because they hate Jesus,’ Christian says in viral Facebook video

With $1 million at stake, U. of Missouri’s president now taking protests seriously