Narrative Detachment in Naturalism
Keep those characters at arms' length, Naturalists. We all know that they're going to suffer horribly.
The Naturalists were influenced by scientific thought in general, and Charles Darwin's theory of evolution specifically. The Naturalists' interest in scientific ideas totally influenced their narrative style.
In Naturalist work, we'll often find that the narrative tone is kind of detached and clinical. The narrator just describes what's going on—he or she doesn't get too involved with the characters, and doesn't even take sides. The narrative tone, in other words, is quite "scientific." Naturalists tend to treat society as though it were some bacteria growing in a petri dish. They analyze it, they describe it, but they don't too emotional over it.
Chew On This
Émile Zola, in his preface to the novel Thérèse Raquin, explains why he wrote about his characters in a detached way. Have a look at his arguments here.
The narrative voice of John Steinbeck's The Grapes of Wrath is pretty detached. The narrator speaks in short sentences, which describe rather than judge. Dive right into these quotations from the book here.