There are lies, damn lies, and confabulations. The difference between them? The confabulators, especially the ones that have Korsakoff's Syndrome, believe that they are telling the truth. This is a syndrome that allows you to lie, consistently, and never know that you're doing it.
Korsakoff's syndrome tends to pop up in patients who have been malnourished or are long-term alcoholics. Both have been unable to absorb enough vitamin B1, and have sustained specific kinds of brain damage. The damage, although it results in destruction of short-term memory, isn't apparent to either the patient or to anyone who talks to them casually. When asked about recent events, the Korsakoff's patient rattles off a plausible and comprehensible story. If the questioner knows the story isn't true, and proves it, they evade further questions and change the subject. The questioner might think they're lying for reasons of their own.
They're not lying — at least not in the sense that they are intentionally misrepresenting the facts. Korsakoff's patients respond to questions with confabulations. Confabulations are an amalgam of past memories and general associations that a person spins into what they consider their reality. Kosakoff's patients in hospitals, when asked what they did that morning, will either talk about long-ago business meetings, say they went visiting old friends, or just say they went to the zoo or a movie. When told that they have been in the hospital for weeks, they claim there has clearly been some mix-up, saying they need to glance at their calendar or talk to their spouses or children to check what the problem is.
The syndrome will extend past personal experience to stories that are told to Korsakoff's patients. One experiment required patients to remember, for forty-five minutes and then for a week, a three-line story about a woman who was mugged. While some patients forgot it entirely, Korsakoff patients tended to add on extra details that hadn't been in the original story. They'd say the woman was mugged in a certain place, or make up names and ages of her children. They saw these as part of the original story, and didn't believe that what they had said was false.
If you're reading this, I'm guessing that, although the misremembered weekend aspect of Korsakoff's may have raised your eyebrows in incredulity, the second story reminded you of some time when you falsely remembered an extraneous detail. We all confabulate. Almost everyone reading this has "remembered" a scene from a movie or a book that never happened, or "remembered" something happening at a certain event and then seen pictures proving their memory was wrong. In many Korsakoff's experiments, doctors have to include neurotypical people to assess the baseline level of confabulation and have to specify that Korsakoff patients are only different in that they confabulate more and confabulate specifically about recent memories.
It appears that drawing a blank slate, mentally, is its own type of mental function. We have to realize that we don't know something. If we don't realize this, like Korsakoff's patients, we will mentally keep sifting through our thoughts until we find a detail that seems to fit and slot it in. Korsakoff's patients are more egregious in their mis-remembering, but they aren't exclusive. Our unrecognized blank slate just lies farther back.
Via Journal of Neurology, Neurocase, and Neuropsychologia.