Maybe you were like me, reading the Ray Bradbury short story for the first time, “There Will Come Soft Rains.” You read about the robot characters in the house faithfully tending to the humans who are long gone. Then [SPOILER ALERT] a robot reads a poem, then the house burns to the ground.

The poem the smart house reads to the absent human dwellers happens to be a real poem, one in which the story is named after: “There Will Come Soft Rains” by Sara Teasdale. It’s one of my favorite poems, and one of my favorite short stories. But in Bradbury’s story, why bother reciting a real poem, let alone referencing one? Why doesn’t he just have the robots recite one he made up?

Authors do this a lot. They love referencing other works. A good author is likely going to reference another author’s work in a fictional story, even when they don’t have to, even when it’s not essential to the plot, even when they could easily come up with something similar that is their own. So why do it?

They want you to check out the other author

Quoting another work, or having another character possess or refer to another work, is one neat way a writer can encourage you to read another writer. Sure, they can come right out and say it on their social media, or in an interview, but if they just sneak it in there, you may find it more irresistible.

If you read A Head Full of Ghosts by Paul Tremblay, you absolutely know by the end that he wants you to get you a copy of We Have Always Lived In the Castle by Shirley Jackson. He won’t stop referencing it for us.

Others have said it better

Using the words of another, or even pointing at the work of another, is a respectful in-story way to admit that perhaps a part of what you’re trying to say, another might have said it better. There comes a time when you have to pause you and let another take over for a brief moment.

Such a moment may be in Bradbury’s story, named after the poem his robo house recites to its dead dwellers. Perhaps the poem’s message meant so much to him that he decided to re-couch it in a sci-fi genre, like a post-apocalyptic shrine.

It’s a fun game

Can you recognize the reference? Authors like to play games with readers to see if they can catch a reference or already recognize another work. Readers who recognize the other work get that special treat of knowing they spotted a little bonus treasure.

There’s a fun little moment in Needful Things where a character has scribbled graffiti on a wall that reads “Yog Sothoth rules!” You can just see author Stephen King grinning, wondering how many readers will get the reference to the work of fellow horror writer H.P. Lovecraft.

Maybe they’re being pretentious

For every cool Shakespeare reference, there’s a self-inflating Shakespeare reference. I’ll admit it. As a writer, it can be tempting to draw attention to another work, as if to say one of the following:

• I have read this work
• I understand this work
• My work is like this work

Maybe The Smiths did this in their song “How Soon Is Now,” which is itself a B-side song. Their line, “I am the son / And the heir / Of nothing in particular,” is a paraphrase from the novel MiddleMarch: “To be born the son of a Middlemarch manufacturer, and inevitable heir to nothing in particular.”

It sounds a little bit hipster to compare your song lots of people won’t hear to a novel most people haven’t read.

They can’t help it; books are made of other books

The compulsion is one writers often can’t avoid, as it’s in our nature. As Cormac McCarthy once said, “The ugly fact is books are made out of books, the novel depends for its life on the novels that have been written.” Funny that he called it ugly, as if it’s a hard pill to swallow for authors that we rely on other authors.

All artists do rely on each other. It is a collective effort. Hence why we feel compelled to build off one another. Even McCarthy, genius writer that he was, drew from all kinds of inspirations, from Faulkner, to Melville, to Steinbeck, to Milton.

The fact of the matter is, we writers can not help but signal each other, and for endless reasons. But these may be the big five. And sometimes we’re doing them all at once. See how many you can spot next time you read a book.