Many times when people are ignorant, or lacking awareness or knowledge, they do not know how to act or what to say in certain situations. In the setting of the 1930's, people who were poor were much more isolated from the conventional wisdom and manners of their times than they are today; consequently, they would exhibit behavior and say things that demonstrated their ignorance.
In Chapter 3, Scout wants to retaliate against Walter Cunningham, because she was punished by Miss Caroline after she tried to explain why Walter had no lunch, as well as why he would not accept the offer of a quarter. At lunchtime, Jem sees Scout trying to punish Walter due to her scolding from the teacher; he stops her. After learning why Scout has attacked him, Jem graciously invites Walter to their house to eat with them. Then, while they eat, Walter asks for syrup. Scout watches as "Walter poured syrup on his vegetables and meat with a generous hand. He would probably have poured it into his milk glass had I not asked what the sam hill he was doing" (Ch.3). Poor Walter does this because there probably is not enough food for him at home, so by pouring syrup on top of it, he adds calories and feels fuller with less food. Because he has become accustomed to this taste, Walter is ignorant of good manners when he is a guest, and he does not know better than to cover the wholesome taste of the food at the Finches' house.
Of course, no one epitomizes ignorance and poverty more than the Ewells. In their efforts to not fall beneath the level of the black population with the white community, they make a charge against a black man before he can say anything publicly about them. Then, in the courtroom, they both show their ignorance with their poor thinking skills, lack of vocabulary, and lack of social skills. For instance, Bob Ewell does not know the meaning of ambidextrous, nor does he understand the reasoning behind Atticus's questioning him about which hand he uses to sign his name. Later, Atticus has one part of Sheriff Tate's testimony read back to Bob Ewell by the court reporter.
“…which eye her left oh yes that’d make it her right it was her right eye Mr. Finch I remember now she was bunged.” He flipped the page. “Up on that side of the face. Sheriff, please repeat what you said; it was her right eye I said—”
This testimony demonstrates that someone who is left-handed struck Mayella in her right eye, and in his lack of understanding of why Atticus has this testimony read to him, Bob Ewell says that he agrees with Sheriff Tate's testimony. By doing this, in his ignorance, Ewell has unknowingly implicated himself as the source of Mayella's black eye.
Mayella also exemplifies the stultifying effects of poverty when she takes the witness stand. First of all, she is frightened by Atticus. When Judge Taylor asks her, "What are you scared of?” she demonstrates that she has not understood the purpose of Atticus's questioning, although she knows that he is against them.
Mayella says something behind her hands.
“What was that?” asked the judge.
“Him,” she sobbed, pointing at Atticus.
She nodded vigorously, saying, “Don’t want him doin‘ me like he done Papa, tryin’ to make him out left-handed…”
Her speech causes even little Scout to wonder if she has "good sense." Judge Taylor scratches his head, and he explains to Mayella,
“Mr. Finch has no idea of scaring you,” he growled, “and if he did, I’m here to stop him. That’s one thing I’m sitting up here for. Now you’re a big girl, so you just sit up straight and tell the—tell us what happened to you."
Ironically, in her ignorance of the law, Mayella has no anxiety about lying under oath and accusing poor Tom Robinson of a crime for which he can be put to death.