If you're smashing your face into the keyboard trying to come up with a brand-new invention, you need to stop and go for a walk. You could also try watching a movie about an unrelated topic. A new book on the process of invention, Inventology by Pagan Kennedy, reveals that roughly half of all inventions started as ideas or discoveries that people had while working on something else.

As Kennedy writes in a recent New York Times article:

One survey of patent holders (the PatVal study of European inventors, published in 2005) found that an incredible 50 percent of patents resulted from what could be described as a serendipitous process. Thousands of survey respondents reported that their idea evolved when they were working on an unrelated project—and often when they weren’t even trying to invent anything.

Kennedy's book, which grew out of a series of articles for the Times about unusual inventions, explores how people invented everything from sliced bread to the airport wheelie bag. The thread that runs through all of the inventors' stories is what Kennedy dubs "serendipity," or stumbling across an idea by chance. The question is whether this kind of serendipity can actually be fostered and encouraged or must simply strike like lightning.

During a lecture in San Francisco last month, Kennedy emphasized that the process of invention has been "democratized." Using crowdsourcing, maker spaces like TechShop, and services for building prototypes, inventors can create new devices without huge amounts of investment capital—or even employees. That said, it actually matters who is in the room when people brainstorm ideas for new inventions. She explained that the first over-the-counter pregnancy tests, designed by men in the 1960s, were all non-starters until a female product designer perfected a form of industrial design that would sell.

The PatVal study also underscores that the biggest source of inspiration for innovators comes from clients or users, people who will actually be using whatever the inventors create. At the other end of the scale are academic and research institutions, which inventors credit with inspiring very few new ideas. So aspiring inventors may be much better served by chatting with users about what they want rather than getting a fancy MBA.