Ackley is one of Holden’s classmates at Pencey, an awkward boy with few social skills. He’s an outcast on campus, never invited to activities and not even granted a nickname. In response, Ackley becomes defensive and misanthropic, complaining about and insulting the other students. Despite this unpleasant behavior, Holden is respectful and humane to him. He invites Ackley to go to the movies with him and Mal, and even attempts to turn Stradlater’s rude comments about Ackley’s teeth into constructive advice. In this way, Ackley gives us an important glimpse into Holden’s character. Even though Holden’s behavior throughout the novel is often self-centered, the way he treats Ackley shows that he can be caring and even protective. He may not find Ackley particularly pleasant or interesting company, but he nevertheless has the empathy to include Ackley when the other boys will not.
However, not all of Holden’s motivations for his kindness toward Ackley are selfless. Holden becomes markedly nicer toward Ackley after he learns of Stradlater’s date with Jane. Ackley, with his poor hygiene and lack of social niceties, is someone whom Holden can always compare himself favorably with. He does not make Holden feel insufficiently manly, unlike the handsome, popular Stradlater.