Need to fill a leadership role in your company? Your first instinct may be to give the job to the candidate who seems most confident and sure of his or her own abilities. But before you make your decision, give serious consideration to a less confident applicant. You may wind up being very happy you did.

Let's say you need to promote someone to be head of a department or area of your business. Of two employees in line for the job, one says: "Please give me this chance, boss! I'm ready to take on this role and I know I will do a great job." The other says: "I would love that job, but I'm not sure I'm ready. I know there will be a lot of challenges, and a lot of unknowns."

Which candidate should you choose? Most leaders' first instinct might be to hire or promote the confident person. After all, your employees are likely to be better judges of their own abilities than you are. You might assume the confident employee has given the job a lot of thought and already planned out what the first priorities should be. And you might assume that the less confident person is aware of shortcomings that could hamper his or her performance.

While both of these seem like perfectly reasonable assumptions, there's a good chance they're completely wrong. Here's why you should at least seriously consider giving the job to the employee who isn't certain of being ready for it:

1. You'll avoid promoting people based on their gender.

There's ample evidence that men in the workplace are generally more confident of their own abilities than women are, and that men will put themselves forward for a job for which they are not completely qualified, while women will hesitate to do so even when they're over-qualified. 

Hubert Joly, Best Buy's executive chairman and former CEO, widely credited with turning the company's fortunes around despite competition from Amazon, made that point during a CNBC event this past summer. "If a boy--I'm going to say a 'boy'--is 80 percent ready for a promotion, he says, 'I'm ready,'" Joly told CNBC's Courtney Reagan. "If a woman is 125 percent ready for promotion, she will say, 'Oh, I'm not sure.' So as a leader you need to be able to recognize this and reach out to the women on the bench and say, 'You know, Corie, you're ready. And I'm going to support you.'"

"Corie" is Corie  Barry, whom Joly chose to replace him as CEO. Barry has 20 years' experience at Best Buy, working in the company's finance department for years, learning operations at the store level, leading the Geek Squad, and becoming CFO in 2016. She's now one of the very few female CEOs of a Fortune 100 company, and at 44, also the youngest. She recently made headlines by projecting that Best Buy would reach $50 million in annual revenues by fiscal 2025.

2. Too much confidence is a sign of stupidity.

You've probably heard of the Dunning Kruger Effect, the phenomenon in which incompetent people who are too incompetent to know what they don't know express great confidence in their own abilities. As a leader, you should always be aware that employees can fall victim to this fallacy. It could be that someone who expresses great confidence has great abilities to back up that self-assurance. But the opposite could also be true.

3. No one really has the answers.

Gartner research VP Irving Tyler recently described to me some surveys the firm had done with executive leadership. The conclusion they reached amounts to this: What got you here won't get you there. "Most executives live in a world where you can solve a problem by the complicated solutions approach," he said. "You line up experts, the experts give you options and you pick one."

That approach doesn't work so well anymore, he said. "Today it requires innovation, experimentation, and failure. I believe executives don't have the tools and experience to succeed in this highly complex, dynamic environment."

Barry made a similar point in her own CNBC interview. "People want this level of confidence that frankly just isn't possible in business, and it's why I start with [the advice of] making yourself uncomfortable," she said. "Because somewhere in here you're going to have to put yourself in a space that you don't quite feel ready to fill, and then leverage all the resources around you to help you be successful." 

Someone who goes into a leadership role feeling less than completely confident is likely to recognize those uncertainties and draw on those resources earlier rather than later. But someone who takes the job feeling certain that he or she has everything figured out may try to do it all alone. Which would you rather have in a crucial role?