The Pervasive Effect of Priors: Part Three
My partner Eric and I were traveling in Portugal in a rented car. The car only took diesel fuel, and we had difficulty figuring out whether particular pumps dispensed diesel. Eric tried to use one pump, which didn’t seem to fit. We asked an attendant, who seemed quite surly. He shoved the ill-fitting pump into the car. About 20 minutes later, on the highway, the car stopped working. The repair people who came to help us told us that the car had been filled with regular fuel.
Eric and I decided that the attendant had disliked us, perhaps because we were American, and had done this on purpose. My sister heard this story; her take was that surely the attendant just made a mistake. She asked ‘don’t you prefer to think of it that way’? Eric and I didn’t, but she did.
One suggestion that’s been made about the marathon bombings is that they could have been stopped given what the FBI knew or had reason to know about the elder brother. Is this comforting—or not? Do we prefer to think somebody knew enough, but didn’t act on their knowledge? Or would we prefer to think that it could not have been stopped?
My point is this: people form narratives to help them make sense of the world, which includes getting some form of ‘comfort.’ How we interpret evidence will be influenced by what sorts of narratives we are forming, as much as what sorts of narratives we are forming will be influenced by evidence.
And what sorts of narratives we are inclined to form will relate to our priors about what sort of world we live in, including what sort of people live in the world. The narratives will also reflect what sort of world we prefer to live in, and what sort of world is easiest for us to navigate. I would rather live in a world where I am disappointed sometimes when I think people are generally good than a world in which I always expect the worst.
But I also think I live in a world where people who are paid to do some very simple thing know how to do it – the alternative, of thinking some gas station employees might not know how to distinguish between two different types of gas pumps where both are commonly used, would make me feel I had to check for all sorts of things I take for granted, vastly complicating my daily life. It is easier for me to think that there are a small number of people who might want to do some bad things to their customers. But my sister formed a different narrative, for reasons of her own.
Returning to the issue of whether the marathon bombings could have been stopped: I don’t know how much comfort I get that the FBI had the elder brother on its radar given that the brothers were able to pull off the bombing. It will be interesting to see how people come to understand what happened. “Facts” will matter, but people may hear the same facts, and spin quite-different narratives.