Why do Holocaust deniers, young Earth creationists, people who think they’ve lived past lives as famous figures, people who claim they’ve been abducted by aliens, and people who stake their lives on the power of homeopathy believe things that most of us do not? David McRaney investigates.

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Put your right hand on your head. Unless you are near a mirror, you can no longer see your hand, but you know where it is, right? You know what position it is in. You know how far away it is from most of the other things around you. I'm using the word "know," but that's just for convenience, because you don't actually know those things. That is, you can't be 100 percent certain your hand is on your head. You assume it is, and that's as good as it is going to get – a best guess. We'll come back to that. You can put your hand down now.

I once interviewed the great neuroscientist V.S. Ramachandran, and asked him about a condition known as anosognosia. This is the term for a disorder that causes the sufferer to deny another disorder. Blind people will sometimes believe they are not, for example. I asked him about this because I had learned that he once treated a patient with paralysis of one arm who denied that the arm was paralyzed even though she couldn't move it when asked. She could no longer make an emotional connection to her arm. She denied that the arm was even a part of her. That biological connection, that feeling of ownership, was missing from her mind, and when asked whose arm it was she would say it was her mother's or her brother's. She said someone was playing a prank on her from under the table. Patients like this will explain away obvious things, but never seem to come out and say something like "it is my arm but I can't feel ownership of it." If she looked at her arm she could see the facts of the matter, but facts couldn't alter her narrative. This is a form of anosognosia, and in these cases family and friends who are on one side of reality have a difficult time understanding how those on the other can continue to believe as they do. Inside the head of the sufferer, it's not an easy thing to realize they are wrong. One of the defining features of anosognosia is that facts often don't work on those who suffer under its terrible spell. I asked Ramachandran how that could that be possible.

Ramachandran said I should imagine a general on a battlefield, about to give the command to attack when an advisor approaches. The advisor tells the general that one of their scouts now says the enemy is stronger than initially believed, and that the attack should be postponed. The general decides that the chances of this one scout being right isn't worth the cost of delaying the attack, and decides to ignore him. Ramachandran then said to imagine that the scout instead says he saw that the enemy had nuclear weapons, and believes as soon as the battle starts the enemy will launch them. Now, in this scenario, the general decides it would be a bad idea to continue, and decides to believe the scout. In a typical brain, he said, the general is careful not to overreact to reports coming in from the field; many of your strange psychological mechanisms serve to keep you on-task in this way, phenomena like denial and rationalization. But if a report is serious and reliable, the general puts all that aside, suppresses it, and responds appropriately. Except in some people the general inside their heads doesn't do that. Damage to the right parietal seems to make it so the brain can't properly gauge when a situation has become too serious to depend on rationalization and denial. Those sorts of brains keep on confabulating, and that's why people who are blind can somehow continue to believe they are not despite what seems like irrefutable evidence to those of us on the outside of their skulls. That's how come a person can deny her arm belongs to her even though it is physically attached at the shoulder.

V.S. Ramachandran also writes about treating patients who have lost limbs, often an arm, but the maps of their bodies do not get updated after the loss. The brain continues to generate a virtual arm, a representation that was once grafted onto flesh. That's what you felt when you put your hand on your head. That's the difficult truth to accept, that there never was a real arm in the first place, at least, not in the brain…it was always virtual, it was always a model, the only difference now is that the model represents something that no longer exists, and it can't be updated. The sensory organs that used to provide the information that updated the model have been lost, yet the model remains.

To borrow from Ramachandran's battlefield, the agencies of your mind are kind of like a general surrounded by lieutenants, all receiving news of the world by messengers, but the whole group is trapped in a war room and only able to interact with a map of the battlefield populated by models of tanks and little toy soldiers. That's what it is like to be a brain. You are trapped in a skull, unable to actually interact with the world outside. You depend on messages from sense organs written in code. When you decode the messages, you alter the map and the models, but that's all you can ever hope to know about the outside world – that map and those models. The evidence gathered so far suggests that one of the most important discoveries in neuroscience and psychology is that you often mistake your interactions with the world to be direct and intimate, and your sensations to be perfect replicas of the elements of the world that your senses perceive. In other words, you sometimes believe that the map in your war room isn't a map at all, that it doesn't represent anything outside of itself, but that it actually IS the real world.

Once you understand that the brain generates a model that is a representation of a more complex and nuanced reality, you can see that your interactions are broad and blunt, approximate and presumptuous, and probably wrong in many ways but in the end, good enough. That's as much as neuroscience is willing to give you – good enough. Your narratives and strategies and memories and actions and decisions and judgments, they are good enough.

All you can ever know about your own body, or the world outside of it, is what your brain tells you, and your brain doesn't tell you the truth. It just makes an approximation, it makes a model of the world. This is where belief begins. If you drill all the way down. If you dig until you reach the rock, your original faith, your central belief, is in your model of reality, the one generated by your brain. That is your terminal dogma: your faith in your internal representations of the world around you. It isn't limited to ownership of your limbs or the belief that your hand is on your head when you place it there. Who is right, you ask, when your messengers arrive, the people telling you vaccines are harmful or those telling you that they are harmless? Who is right, the climate scientists or the politicians who distrust them? Locked in the skull, its only interaction with the world based on models and maps, your brain can only make best guesses that are good enough.

Our guest for this episode, Will Storr, wrote a book called The Unpersuadables: Adventures with the Enemies of Science. In that book, Storr spends time with Holocaust deniers, young Earth creationists, people who believe they've lived past lives as famous figures, people who believe they've been abducted by aliens, people who stake their lives on the power of homeopathy, and many more – people who believe things that most of us do not. Storr explains in the book that after spending so much time with these people it started to become clear to him that it all goes back to that model of reality we all are forced to generate and then interact with. We are all forced to believe what that model tells us, and it is no different for people who are convinced that dinosaurs and human beings used to live together, or that you can be cured of an illness by an incantation delivered over the telephone. For some people, that lines up with their models of reality in a way that's good enough. It's a best guess.

Storr proposes you try this thought experiment. First, answer this question: Are you right about everything you believe? Now, if you are like most people, the answer is no. Of course not. As he says, that would mean you are a godlike and perfect human being. You've been wrong enough times to know it can't be true. You are wrong about some things, maybe many things. That leads to a second question – what are you are wrong about? Storr says when he asked himself this second question, he started listing all the things he believed and checked them off one at a time as being true, he couldn't think of anything he was wrong about.

Storr says once you realize how difficult it is to identify your own incorrect beliefs you can better empathize with people on the fringe, because they are stuck in the same predicament. They are just as trapped in their own war rooms, most of the time unaware that the map they use is, as psychologist Daniel Gilbert once said, a representation and not a replica. They are judging the evidence presented to them based on a model of reality, a map that they've used their entire lives, and you can't just tell someone that his or her map is a fantasy realm that doesn't exist and expect them to respond positively. You can't just ask a person like that to throw away that map and start over, especially if they've yet to realize it is just a map, and their beliefs are only models.

In this episode we ask experts where do our beliefs come from, how do we know where we should place our doubt, and why don't facts seem to work on people? We explore the psychology of belief through interviews with Margaret Maitland, an Egyptologist, who settles once and for all whether or not aliens built the pyramids. We also speak with Jim Alcock, a psychologist who studies belief itself who explains how emotions and rationality combine to form our concepts of reality.

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