In "Thank You Ma'm", how does Hughes primarily develop his characters?

Langston Hughes was an important name for the Harlem Renaissance, who portrayed the life of black people in America. His short story "Thank You, Ma'am" revolves around the interaction between Mrs. Luella Jones and Roger.

At the very beginning, the author does offer some physical description of the characters - Mrs. Jones is tall and big, Roger is young and skinny. But the real development of the characters does not come through the narration. It is in their dialog that we learn about their reality, their past, and their feelings. Mrs. Jones helps the boy because she knows deprivation, she knows what it is like to steal out of necessity. Roger has a good heart, and is indeed ashamed of trying to steal Mrs. Jones's purse. Her goodness toward him shows him that there are people who trust and who deserve to be trusted in this world.

Their lines are also permeated with dialect, which allows us to build some social background. Below you'll find a brief excerpt:

After that the woman said, “Pick up my pocketbook, boy, and give it here.” She still held him. But she bent down enough to permit him to stoop and pick up her purse. Then she said, “Now ain’t you ashamed of yourself?”

Firmly gripped by his shirt front, the boy said, “Yes’m.”

The woman said, “What did you want to do it for?”

The boy said, “I didn’t aim to.”

She said, “You a lie!”