Analyze the development of the character of Scout. Support this analysis with evidence from the text, such as major developments in the plot.

Whether or not Harper Lee studied Piaget's stages of cognitive development or not, Lee did an admiral job of showing readers a character that is moving from the preoperational stage to the concrete operational stage. The preoperational stage tends to exist when a person is between the ages of 2 and 7 years old. One of the characteristics of this stage is that a child tends to be egocentric and struggles to see things from another person's perspective. When the book begins, Scout is just about 6 years old, and readers can see Atticus trying to help Scout consider things from another person's perspective:

"First of all," he said, "if you can learn a simple trick, Scout, you'll get along a lot better with all kinds of folks. You never really understand a person until you consider things from his point of view—"
"Sir?"
"—until you climb into his skin and walk around in it."

At the book's conclusion, Scout is 8 years old. She has technically moved into Piaget's concrete operation stage which exists between 7 and 11 years of age. It is during this developmental stage when a child begins losing some of their egocentric tendencies. Kids become better at thinking about how other people might feel or see a particular situation. I believe that her final interaction with Boo helps readers see this change in Scout. In the book's final paragraphs, Scout is talking about a character from the story Atticus was reading, but the subtext hints that she is also referring to her newfound attitude and opinion about Boo as well:

"Atticus, he was real nice . . ."
His hands were under my chin, pulling up the cover, tucking it around me.
"Most people are, Scout, when you finally see them."

Scout develops from an innocent, impulsive child to a more knowing and caring young girl as the novel progresses. At the beginning, Scout is somewhat careless with her language and her tone of voice when speaking to others, but by the end of the novel, she is more considered and thoughtful in her speech. This change reveals the development in her character very clearly.
For example, in Chapter 2, Scout doesn't think carefully before speaking out loud in class, and she creates a difficult situation for herself with the teacher and with Walter Cunningham. She means to be helpful, but she doesn't think it all through, and Scout ends up frustrated and tearful at being so misunderstood. Later, in Chapter 3, Scout and Calpurnia clash because, yet again, Scout innocently speaks her mind, and her curiosity about Walter Cunningham's table manners leads to another difficult situation.
An example of change takes place later in the book when Scout shows more thoughtfulness and restraint in her speech, signifying growth and maturity. In Chapter 15, during one of the most poignant moments in the whole novel, Scout speaks carefully and politely to Mr. Cunningham during the mob scene. Her childish good intentions are tempered by her awareness of the men and her learning to be more thoughtful, and she single-handedly contains the mob and the men disperse. Here, the power of Scout's newfound handle on language is apparent as well as her maturing awareness.