In 1887, after achieving great fame and fortune for his invention of the phonograph, a machine that recorded sound, the acoustic telegraph, which transmitted more than one message at a time, and commercially viable light bulbs, Thomas Edison built a laboratory in West Orange, New Jersey. He recruited a team of talented scientists and engineers to help him further develop his famous inventions and, of course, to come up with new ones.

Edison’s team there invented a cotton picker, a snow compactor, and a way of using magnetized iron to generate electricity. But probably the most famous device to emerge from that lab was the kinetoscope, a machine for viewing motion pictures. How, exactly, the engineers designed this machine, and how much of the credit should be given to one of Edison’s assistants, William Kennedy Laurie Dickson, are fascinating stories. But as a writer who constantly struggles to come up with something new, I’m more interested in the machine’s origin story. How did Edison generate the idea in the first place?

We tend to think of inventors as another species—geniuses—who have sudden flashes of insight. I can’t think of a single instance when a light bulb went off in my head, leading to some killer new idea. Is that because I’m an uncreative dud? Perhaps. Alternatively, it might be because Eureka moments are the stuff of legend. According to historians who specialize in the development of inventions and the thought processes of inventors, innovation is often a slow and iterative process.

And what, exactly, is involved in said process? One decades-old theory says that the crux of creativity lies in making analogies. Yes, just like those SAT questions: Crumb is to bread as…splinter is to wood. Medicine is to illness as… law is to anarchy. Creative people, the theory goes, are constantly connecting old knowledge and experiences to new situations. Edison’s kinetoscope, for instance, owes a lot to analogy.

One of the earliest hints of the kinetoscope idea, according to historians W. Bernard Carlson and Michael Gorman, dates to an evening in February 1888, when Edison went to a lecture not far from his laboratory at the New England Society in Orange, New Jersey. The lecturer was Eadweard Muybridge, a British photographer famous for capturing animals in motion. “Afterwards, Edison invited Muybridge to visit the laboratory,” Carlson and Gorman write in a 1990 paper. While Muybridge was at the lab, he mentioned that he mounted his photos in a praxinoscope, a spinning cylinder, to create the illusion of motion. “From Muybridge, Edison learned that motion could be recorded in a sequence of photographs,” Carlson and Gorman write.

Recording motion, Edison realized, was not so different from recording sound, which he had already done with his phonograph. Eight months after meeting Muybridge, Edison spelled out the analogy in a preliminary patent for the kinetoscope: “I am experimenting upon an instrument which does for the Eye what the phonograph does for the Ear, which is the recording a reproduction of things in motion, and in such a form as to be both cheap, practical and convenient,” he wrote.

Many other great thinkers have also used analogies to great effect. In their book Mental Leaps, cognitive scientists Keith Holyoak and Paul Thagard cite Vitruvius, a Roman architect, as the first person in recorded history to use an analogy to drive a scientific theory. In describing, more than 2,000 years ago, how to best build a theater, Vitruvius proposes that voice sounds are like ocean waves. “As in the case of the waves formed in the water, so it is in the case of the voice,” Vitruvius wrote. “The first wave, when there is no obstruction to interrupt it, does not break up the second or the following waves, but they all reach the ears of the lowest and highest spectators without an echo.”

Johannes Kepler, a great astronomer of the late 16th century, also loved a good analogy. One of his most famous came about when he was trying to understand why planets furthest from the sun move slower than those closest to the sun. He thought it might be due to some sort of spirit coming from the sun. But there was a big problem with this idea. As psychology researchers Dedre Gentner and Arthur Markman explain in a 1997 paper: “For the sun to move the planets would require action at a distance, an abhorrent notion to any physical scientist.” Kepler got around this problem with an analogy: What if that sun-centered spirit (later known as gravity) was like light? Just as light can travel invisibly from the sun to illuminate a given place, Kepler proposed, a force could travel from the sun to a planet and affect its motion.

OK, so analogies seem to work well for some folks. But why would analogy lead to new ideas? According to the analogy theory, it’s because making analogies requires thinking across traditional mental categories. In fact, some cognitive scientists have proposed that the farther the analogy—that is, the farther apart the previous experience and new situation—the more likely it will lead to a radically new idea.

The analogy theory makes intuitive sense, but there’s not much empirical evidence to back it up. Most of the scholarship comes from historians looking closely at the writings of famous people like Edison, Vitruvius and Kepler. But a new study in the journal Cognitive Science tries to provide some concrete, on-the-ground data by taking a very thorough look at how people brainstorm.

Joel Chan and Christian Schunn of the University of Pittsburgh analyzed several hours of video tape of a real-world design team. The team included 10 people with a range of expertise—from electronics, mechanical engineering, business consulting, ergonomics, and industrial design—who were working on creating a new hand-held printer that could be used by children.

Chan and Schunn perfumed a word-by-word analysis of the designers’ conversations, mapping out how one thought led to the next. They found that the far analogy theory didn’t apply to this team. When group members used far analogies (such as comparing part of the product to a garage door), they were not more likely to reach radical new ideas than when they used other kinds of analogies or no analogy at all. In fact, far analogies tended to precede fairly incremental leaps in thought.

But that doesn’t mean the far analogies weren’t useful; far from it. It turns out that far analogies helped the designers make a series of related, incremental connections, rather than leaping over big concepts. That didn’t make sense to me until I read some of the snippets from the transcript. Here’s one, for instance, where the garage door analogy leads to a roller door analogy, allowing the designers to refine a new idea:

Todd: I’m thinking of something a bit like erm the flap on a video tape

(Pause)

Alan: uh-huh what the flap?

Todd: yeah

Tommy: like a garage door type of thing

Todd: yeah push the button, then it goes open

Tommy: yeah

Todd: but that’s probably overly complicated

Rodney: garage door, well it could be a roller

Todd: a roller door

One of the implications of this study, the authors note, is that incremental thinking can be crucial for innovation. “We might infer from the present data that incremental accumulation of many small insights is at least as likely to lead to innovative outcomes as direct generation of very novel concepts,” they write.

I don’t know much about business and engineering, but this absolutely jibes with my experience as a writer. For me, writing is just a series of connections.