Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
More Serious Than a Heart Attack
The tone or attitude Faulkner writes this story with is so serious you'd think he was carving his words into granite. Notice, for example, the absence of jokes. Some of the children's behavior might give you a tiny wry grin, but definitely not much more. But hey, Faulkner is tackling some serious issues.
Consider these ponderous sentences, for example: "Father came in. He looked at us. Nancy did not get up." (5.1). Very matter-of-fact; no room for doubt. Of course, that the words are so definitive doesn't prevent the story from conveying shades of meaning and ambiguity. It just lets us know there's no kidding around.
The use of a serious tone makes sense because of the weighty themes the story is taking on. You can't really joke about a terrified black woman being abandoned by a white family who thinks it's no big deal to leave her suffering alone.
So we give Faulkner an A+ for keeping his serious hat on.