Between Doubt and Illusion: Why Does the Brain Invent False Memories?
Have you ever wondered if something really happened, or if your mind just made it up? Today, we return to the topic of false memories and confabulation, exploring with neurobiologist Jules Montag how the brain checks the accuracy of information, what happens when these checks fail, and why strong emotions can cloud our critical thinking. We’ll also look at how brain injuries can make people unable to doubt even the most unrealistic ideas, and why we sometimes not only believe what we’re told, but fiercely defend those beliefs.
What Is Confabulation?
During a hospital round, Maggie told her doctors how she had visited Madonna’s mansion the previous week to help pick out costumes for her tour. The only problem? Maggie is a seamstress in Dublin who has never met Madonna, let alone advised her on cone bras. An MRI performed days earlier, after Maggie was admitted to the ER with a fever, revealed she had encephalitis—an inflammation of the brain.
As a result of her brain injury, Maggie’s real memories became tangled with invented stories. No matter how absurd her tales of being a celebrity tailor sounded, Maggie believed them completely. This is the essence of confabulation—the inability to think critically about one’s own memories. What others saw as obvious lies, Maggie experienced as undeniable truth.
The most severe forms of confabulation are caused by brain damage from encephalitis, stroke, physical trauma, or a lack of thiamine (vitamin B1) due to chronic alcoholism. Some patients invent truly fantastic stories—claiming to have been a spaceship captain in a past life or to have met aliens and UFOs. Their memories and sensations from the past blend into the present, distorting reality.
How the Brain Checks Reality
The phenomenon was first described in 1889 by Russian psychiatrist Sergei Korsakoff, who reported on a patient who, after visiting Finland, mixed in memories from Crimea, resulting in the belief that Finns eat lamb all the time and are Tatars by ethnicity.
Like Korsakoff’s patient, many people with confabulation embellish reality, add small details, or simply mix up facts—in ways that aren’t so different from the rest of us. Normally, our intuition helps us quickly judge what’s real and what’s not. When we encounter something implausible—like seeing a kangaroo on the way to Edinburgh—our brain automatically raises a red flag: “Did I really see that?”
Subconsciously, we double-check such information using so-called doubt tags, which are linked to the orbitofrontal cortex and medial prefrontal cortex of the brain. These areas signal when “something’s not right.” In people with confabulation, these brain regions are damaged, making them unable to doubt even the most outlandish ideas.
False Memories in Healthy People
Brain injury isn’t the only cause of confabulation. Young children often show similar tendencies, likely because their prefrontal cortex is still developing. Researchers at Bedfordshire University (UK) and the University of British Columbia (Canada) recently managed to convince a group of healthy students that they had a criminal past.
First, participants were told about a real event from their youth, with details provided by family members. Then, they were fed a fabricated story about a police-related incident, supposedly recounted by their parents. Participants were asked to describe both events in detail—real and fake.
By the third interview, 70% of participants showed signs of confabulation, admitting to theft, assault, or threatening someone with a weapon—crimes that never happened. With each retelling, the stories became more vivid and believable.
“I remember two police officers. There were two of them,” one participant said. “I’m sure of it… I think one was white, the other maybe Latino… I remember getting into trouble. I had to tell them what I did…”
“Do you remember screaming?” the interviewer asked.
“I think she called me a slut,” came the reply. “I was furious and threw a rock at her. I did it because I couldn’t get closer…”
Why We Can’t Always Trust Our Memories
The inability to check certain memories is a problem for both people with confabulation and healthy individuals. William Hirstein, a philosopher and cognitive scientist at Elmhurst College in Illinois, calls this the “failure to reject the flawed response.”
This is especially true for memories that inspire us, are suggested to us, or arise under pressure. For example, during police interrogations, an innocent suspect might invent false memories to satisfy the request to “give your best guess,” leading to false testimony.
Strong emotions can greatly affect our doubt tags. They determine how vivid and real a memory feels, and how deeply we can recall and immerse ourselves in it. People often become extremely confident during heated arguments. But a lack of doubt doesn’t mean something is true.
The Evolutionary Roots and Dangers of Doubt
Our tendency to doubt is a product of evolution. Is the growling animal in front of me a wolf? There’s no time to think—just run. But this mechanism has a downside: it makes us vulnerable to deception. People with damage to the medial prefrontal cortex are twice as likely to believe false advertising, regardless of their education or memory skills.
This may explain why older adults are more susceptible to scams. As we age, the structure and function of the medial prefrontal cortex decline, dulling our ability to doubt.
Confabulation and Its Ethical Consequences
Even without brain injury, confabulation and a lack of doubt have moral and ethical consequences. In a 2012 experiment at Lund University in Sweden, participants were asked to rate their agreement with statements about war, immigration, government surveillance, and prostitution. Unbeknownst to them, their answers were secretly switched to the opposite stance.
After reading their (swapped) answers aloud, participants were reminded of their supposed views. Astonishingly, 69% failed to notice the switch at least once and began defending the opposite viewpoint. This is called choice blindness—when we don’t notice discrepancies between our choices and their outcomes, and then adopt new beliefs as our own.
A week later, participants with confabulation symptoms accepted the false choices even more readily. As cognitive scientist Petter Johansson explained, when we form arguments to defend ourselves, we influence not only others but also ourselves. Our values may change not through conscious choice, but through rationalization—a defense mechanism that helps us maintain self-respect by mistaking wishes for reality.
Eye-tracking analysis showed that most people who experienced confabulation didn’t notice the manipulation. This is alarming: while a lack of doubt can save us from a wolf, it also makes us easy targets for deception.
The Value—and the Risk—of Doubt
The ability to doubt is undeniably valuable. It drives us to form hypotheses and demand evidence, pushing science forward. As medieval philosopher Peter Abelard said, “Doubt leads to inquiry, and inquiry leads to truth.”
Hirstein unexpectedly links doubt to the “fight or flight” response. Doubt doesn’t just affect our thinking—it triggers uncomfortable physical sensations, as if something is gnawing at us from the inside. Perhaps these feelings are why we rethink our words and actions.
But doubt is a double-edged sword. A whirlpool of conflicting opinions can drag us into a sea of uncertainty, making us easy prey for manipulators. As tobacco company Brown & Williamson declared in 1969, “Doubt is our product, since it is the best means of competing with the ‘body of fact’ that exists in the mind of the general public.”
How to Manufacture Doubt
Here’s the recipe for creating doubt: Put words like “expert” and “data” in quotation marks. Add a couple of paid critics. Praise their courage. Highlight the contradictions in their research. Encourage “healthy skepticism.” Mix well. Done! You’ve just made your opponent question everything—without needing facts or arguments.
Maggie’s fever eventually passed, as did her fantastic stories. Her ability to doubt was restored, though at the cost of trading one vulnerability for another. But it’s better to struggle with doubt than not have it at all. Don’t you think?