For what reasons does Bigger behave toward his family with an "attitude of iron reserve?"

As "Book 1: Fear" opens, we see the entire family waking up early in their cold, cramped, rat-infested room, with the mom hurrying everybody up so she can get to her work. The beds are made of iron, an important detail that we pick up on that makes us wonder what else is, figuratively, iron in this scene. We find out in a moment.

Bigger kills the rat that suddenly appears and terrorizes the...

As "Book 1: Fear" opens, we see the entire family waking up early in their cold, cramped, rat-infested room, with the mom hurrying everybody up so she can get to her work. The beds are made of iron, an important detail that we pick up on that makes us wonder what else is, figuratively, iron in this scene. We find out in a moment.

Bigger kills the rat that suddenly appears and terrorizes the others, but he makes the situation worse by dangling the dead rat in front of his sister Vera.

At that point, Bigger's mother is absolutely clear (even vitriolic) about how she despises Bigger, his foolish behavior, and his utter failure to get a job that would be the family's ticket out of their misery. She calls him "the biggest fool," says he has no manhood in him at all, and wonders aloud why she even gave birth to him.

Then the narrator tells us:

"He hated his family because he knew that they were suffering and that he was powerless to help them. He knew that the moment he allowed himself to feel to its fullness how they lived, the shame and misery of their lives, he would be swept out of himself with fear and despair. So he held toward them in attitude of iron reserve; he lived with them, but behind a wall, a curtain."

There it is, the phrase "iron reserve," meaning "solid, hard restraint and self-control." This makes sense:  Bigger's family situation fills him with such despair that he has to close himself off from it. The only way he can survive is by keeping his mom and siblings separate from himself so that he doesn't become even more paralyzed by their depressing situation.

Bigger's struggle is, as his name indicates, bigger than himself; it illustrates something about the entire social struggle in America that he's a small part of. In the introduction to the novel, Arnold Rampersad notes that Bigger and his entire social class are still suffering from "centuries of abuse and exploitation." Understanding Bigger's attitude toward his family, therefore, helps us start to understand more about the racial and social turmoil that the novel deals with.