What evidence is there that Jody matures from "The Gift" to "The Great Mountains" in The Red Pony?

In “The Gift” Jody is a ten year old, obedient and naïve boy. 
He doesn’t question anything he is told.  He seems satisfied with his
life.

His father was a
disciplinarian. Jody obeyed him in everything without questions of any kind. (ch 1, p
3-4)

When Jody’s pony dies, he is
saddened to the point of not caring anymore.  His father asks him if he knows that the buzzard
did not kill the pony.

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[Billy] lifted Jody in his arms, and had turned to carry
him home. But he turned back on Carl Tiflin. "'Course he knows it," Billy said furiously, "Jesus
Christ man, can't you see how he'd feel about it? (ch 1, p.
34)

As chapter 2 begins, Jody is
“listlessly” looking for something to do.  He begins throwing rocks at Swallow’s nests and
setting mousetraps for the dog to stick his nose in.  He does this not out of meanness, but out
of boredom.  Jody has learned hard lessons about life, but he has also begun to accept life's
difficulties.