Honesty might be the best policy, but that doesn't stop jobseekers from stretching the truth. According to Ron Friedman, an award-winning social psychologist and author of "The Best Place to Work, a whopping 81 percent of people lie during interviews.

That's likely why SpaceX and Tesla CEO Elon Musk asks one simple interview question to catch a candidate's bluff: What were the most difficult problems you faced and how did you solve them?

Speaking at the World Government Summit in Dubai, the tech billionaire said that this "very important" question reveals the role an applicant had at a project or company. From this question, Musk says he can tell whether the applicant was truly the one who took ownership and found solutions to a problem as opposed to simply being a member on a team that did so.

"People [who] really solved the problem, they know exactly how they solved it," Musk explained. "They know the little details." These candidates are able to talk in-depth about the struggles that they faced and the strategies they used. Says Musk, great candidates can answer this question on "multiple levels."

Conversely, those who "pretend" that they were the problem-solvers can "maybe go one level and then they get stuck," said the billionaire.

When candidates can't talk at length, he knows they weren't really the one to work on the challenge. "Anyone who struggles hard with a problem never forgets it," Musk said, touching on this topic at a separate conference.