The primary literary device Carver uses in "A Small, Good Thing" is dialogue. Carver’s style is relatively free of flowery descriptions, including unnecessary similes and metaphors within his sentences.
In this story, hearing what the characters say out loud to one another is a strong tool for indirect characterization. The effect that this has on characterization is especially poignant when a character’s thoughts or actions seem to contradict what he or she has said.
For instance, when Howard says to Ann "Let’s try not to worry," this actually indicates that he is very worried about Scotty. This tells us that Howard is a rational thinker, and in times of stress, he assesses the situation from a logical standpoint and remains calm—even when his emotions are running high.
The only other literary device that Carver uses throughout the story is imagery. Typically, this imagery is used to describe the characters—even minor ones—in exacting visual detail. For example, Dr. Francis is described as wearing a three-piece suit and looks "as if he had just come from a concert." This description allows the reader to visualize the physician, in addition to revealing something about his character. Dr. Francis is a formal, traditional person who speaks politely and concisely, something that begins to worry Ann when she tries to remember if his facial expression revealed something he didn’t say.
Overall, Carver uses sparse literary devices in favor of characterization and narrative. This allows the reader to focus on the message of the story.