Edison began using tests for candidate assessment in the late 19th century, but the questions he asked then were very specific to open positions he needed filled. Over time, he expanded on the idea, including questions that were not directly related to the job. While interviewing research assistants, for example, Edison served them soup to see if interviewees would season the soup before they tasted it; those who did were automatically disqualified as it suggested they were prone to operate on assumptions. In 1921, Edison debuted the Edison Test, a knowledge test with more than 140 questions. Questions varied depending on the job position, but all interviewees were asked about information outside of their areas of expertise. The queries ranged from agricultural in nature ("Where do we get prunes from?") to commercial ("In what cities are hats and shoes made?") to the macabre ("Name three powerful poisons"). After a copy of the questionnaire was leaked to The New York Times, Edison had to change the question bank multiple times to ensure applicants took the exam without any outside assistance.

A score of 90% was required to pass, and out of the 718 people who had taken the test as of October 1921, only 32 (just 2%!) succeeded. The test was difficult, to say the least. Edison's own son Theodore failed it while a student at the Massachusetts Institute of Technology (MIT). More famously, Albert Einstein failed the exam because he forgot the speed of sound. The 1920s saw an upswing in college-educated people in the workforce, leading to increased competition for skilled labor, and thus more applicants for employers to choose from. Edison's strategy of questioning candidates to assess their personality and aptitude was innovative at the time, and is still standard practice today — though employers are more likely to ask about someone's greatest accomplishment than the origins of prunes.

By the Numbers

A World War I questionnaire helped pave the way for the Edison Test.

Thomas Edison wasn't the only person interested in the idea of screening people for specific roles. During World War I, psychologist Robert S. Woodworth developed the Woodworth Personal Data Sheet, a 125-question questionnaire used to determine a recruit's likelihood of succumbing to shell shock, a term coined by soldiers and now known as post-traumatic stress disorder, or PTSD. Woodworth's Psychoneurotic Inventory, as it was also known, was eventually commissioned by the American Psychological Association and is considered to be the great-grandparent of today's personality tests.

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