On March 8, 1998, the Fox television network aired an episode of its long-running animated hit “The Simpsons” titled “Lisa the Simpson.” It was neither the first nor the most famous episode devoted to the show’s fiercely intelligent, spiky-haired eight-year-old middle child but, for pop-culture addicts who love outspoken female characters and recall the particular obsessions and anxieties that come with being a girl of grammar-school age, it was certainly one of the most provocative.

“Lisa the Simpson” probes the potent, heady threshold between childhood and early adolescence, when many girls experience crippling doubts about their self-worth—what the psychologist Carol Gilligan has called “going underground.” In the episode, Lisa experiences a crisis of confidence when she can’t solve a brain teaser, deciding that something terrible has happened to her mind, and that she is doomed to a stifling life of motherhood and daytime-soap-opera watching. “It can’t just be a bad day. I think I’m getting dumber by the minute,” she confesses to her mother, Marge. After a run-in with a female jazz musician who emphasizes the importance of sharing one’s truths with the rest of the world, Lisa decides to deliver a desperate tribute to what she believes to be her quickly deteriorating mental abilities. She scams her way onto a local news program, where she implores viewers to nurture their brains with two wonderful books: “Harriet the Spy” and “To Kill a Mockingbird.”

Lisa Simpson was onto something when she invoked these two novels as an antidote to forgetting, and to forgetting yourself: her character is, after all, a spiritual descendent of both Jean Louise (Scout) Finch, the plucky six-year-old protagonist of Harper Lee’s Pulitzer Prize-winning 1960 novel, and Harriet M. Welsch, the nosy, opinionated, and obstinate eleven-year-old heroine of Louise Fitzhugh’s 1964 children’s classic, which celebrates its fiftieth anniversary this spring. And, in the same way that Lisa has been celebrated as a feminist hero since her creation, by the cartoonist Matt Groening, in 1987, millions of women and girls, myself included, have long considered Scout Finch and Harriet M. Welsch two of the most important American examples of enlightened, audacious girlhood. In fact, I’ve long suspected that “Harriet the Spy” was heavily influenced by “Mockingbird.”

The story of a six-year-old girl observing the oppressive racial politics of the fictional Maycomb, Alabama, in the nineteen-thirties may not seem to much resemble that of a sophisticated, eleven-year-old Upper East Sider taking notes on the petty social mores of her peers in the nineteen-sixties. But the books share thematic concerns—concepts of truth, justice, and self-actualization—as well as a number of details. Both are centered on grade-school tomboys who love denim and sensible shoes. Like Scout, Harriet has an absent—in her case, uninvolved—mother; comes from an economically privileged family; and is contemptuous of frailty and friendly with filth. Both are rough-and-tumble, foulmouthed, mostly male-identified girls who are fascinated by the people in their neighborhood, and both butt up against expectations of their gender—“I’ll be damned if I go to dancing school!” Harriet bellows at one point. And each book argues for authentic expression in favor of fealty to convention.

There is no evidence that Fitzhugh, who died of a brain aneurysm in 1974, at the age of forty-six, ever met Nelle Harper Lee, who is now eighty-seven years old and living in Monroeville, Alabama. Nor is there evidence that Fitzhugh had an opinion about “To Kill a Mockingbird” (Lee’s only book), although she must have been aware of its immediate and huge success; it was published the year before she began work on “Harriet the Spy.” But, half a century after the publication of “Harriet,” I’m convinced that there is a close connection between these two books and their ideas about the complexity, sophistication, and occasional wickedness of young girls’ imaginations.

Anna Holmes is a writer and an editor, and columnist for the New York Times Sunday Book Review.