Perhaps the most obvious example comes when Jem explodes after the expletive-ridden diatribe delivered by Mrs. Dubose against Atticus. Scout
... took umbrage at Mrs. Dubose's assessment of the family's mental hygiene... (Chapter 11)
but she was merely "terrified" by the old lady's threats and general appearance. To her, it was "routine." But
Jem was scarlet. (Chapter 11)
His anger uncontrollable, he took Scout's brand new baton and chopped up Mrs. Dubose's prize camellias. He then turned to the "shrieking" Scout, yanking her hair and threatening to "pull every hair out of my head." Jem was now old enough to understand the implications of Mrs. Dubose's remarks--that Atticus was "lawing for niggers" and "no better than the niggers and trash he works for!" While Scout "had become almost accustomed to hearing insults aimed at Atticus," Jem had just turned 12 the day before, and was no doubt feeling more adult than before. Jem's aggressive act was not in his nature--"he had a naturally tranquil disposition and a slow fuse"--but it was his way of defending the family honor.
Scout seemed to understand the two-sided nature of the Maycomb women better than her brother. While Jem is enamored with the new teacher's good looks, Scout is offended by her lack of teaching skills. She sees first-hand the hypocritical nature of the missionary circle and knows that Aunt Alexandra will always focus most of her attentions on her. Alexandra pays little heed to Jem, who tends to his boyish activities; instead, Alexandra concentrates on Scout, bent on trying to change her unladylike ways.