We research our books. Some crime writer go on a ride-along, take FBI courses, or visit areas they want to write about, to get the little details that make verisimilitude in the story and hold the readers' suspension of disbelief, because after all, if it's fiction, they know it didn't really happen. It's our job to make it feel like it did, or bring it to life in the readers' minds. One of your first readers might be in law enforcement, if you are writing about police. They might be someone who spent time in prison, if you are writing a prison novel. Someone who lives in Alaska, if you are writing a book set there, and only had the time and funds to research it online or by reading. Someone who has lived a life similar to your character.
Which brings up what some are calling "sensitivity readers." It's a first reader who has lived a life similar to your character. But not in their profession, or in their home country or state, but their race, religion, gender, sexual orientation. And a lot of writers chafe at this idea. Some of it is the name itself. What, you sayin' I lack sensitivity? (Imagine that said in my thickest of Jersey accents).
Writers work in empathy, in the original sense. The vicarious experience of another's emotion, through our imagination. And the idea that we'd fail at this strikes at the heart of what we do. Part of what we do is create imaginary people, and they are very personal to us. And the idea that we lack "sensitivity!" That's our bread and butter! We observe, we feel, we create in response to those observations and emotions!
Yes, but we do it through a lens. We don't actually walk in another's shoes, much less their skin. And as hard as we try to shed the beliefs and prejudices we were raised with, there are experiences we can only know second hand. Sometimes we feel like we know these experiences because we've read about them, watched them on TV, and have close friends who have lived it. But that's a lens in front of a lens. Which can be doubly distorted.
A writer I greatly respect responds to this with, "but your 'sensitivity reader' is only one person. Their experience doesn't speak for everyone of their background." And that is true, but their lens is different than ours. Personally, I think this chafing comes from fear. Not at being called a racist, but of finding a cataract in our empathic lens, a blind spot. To me, that's an opportunity for improvement. To learn something about life I can never experience firsthand. And that's why I read.
And I will admit my hypocrisy. One of my more popular characters is Denny the Dent, a hulking African-American man with a birth injury that makes people assume he is developmentally challenged. I have never used a first reader for any of those stories. They've gone directly to editors. Because Denny is based on me. Once I filled out, and my terrible striking defense gave me a pugilist's nose, I noticed that people were intimidated by me. When I went on my nightly walks, lost in my daydream writing world, people would cross the street. When I'm distracted by writing thoughts, I get what my wife calls my "murder face."
So I amplified what I felt, when writing Denny. He's a very sympathetic character. Like his pit bull Remy, he just wanted to be friendly, but the world was cruel. And now he hides inside himself, until he sees a cruelty inflicted upon another that he cannot abide.
That doesn't mean I got everything right. Denny grew up in Newark. I've worked there for decades, but I don't know what growing up in his ward was like. I've read articles by people who grew up in the Terrace projects, and talked to people who have. For a few short stories that may have been enough, but when I write the Denny the Dent novel, a lifetime Newarker like Denny will be one of my first readers. Because I want to get it right. Another lens, when positioned correctly, can let us see the stars. And that's what the right first reader can do.