Melinda Gates almost quit Microsoft in the 1980s because of the combative, male-dominated culture - and even today, bosses reward people who look and act just like they do

• Many bosses exhibit unconscious bias in their hiring and promotion strategies.
• Specifically, they show favor to people who look and act just like them.
• Often the result is that people from privileged backgrounds wind up getting ahead.
• For your own success as well as your organization's, it's important to double-check your gut feelings about coworkers.

Melinda Gates joined Microsoft in 1987. Shortly after, she considered quitting.

Gates, who is co-chair of the Bill and Melinda Gates Foundation, wrote on Quartz that she was the only woman hired in the incoming class of MBAs at Microsoft. She said, "It wasn't always easy for me to feel at home in an environment where people seemed to get rewarded for being combative."

Ultimately, Gates stuck around, and found success by treating people respectfully.

Peggy Johnson, executive vice president of business development at Microsoft, started out with a slightly different approach. She told HuffPost about trying to "elbow my way into discussions, interrupt and raise my voice." Once, she said, "I even pounded my fist on the table, and it was so awkward! Not just for me, but for everyone else in the room, because there's nothing more uncomfortable than watching a person try to be someone they aren't."

For Johnson, that moment was a wake-up call: "To succeed on my terms, it was important that I defined my own brand of leadership."

Gates and Johnson's observations about Microsoft, and what it took to advance there, are hardly unique. Across companies and industries, management is more likely to shine a light on people who look and act just like they do. The result is a more or less homogeneous organization - the opposite of what makes companies thrive - and a frustrating situation for people whose backgrounds and aspirations don't fit that cookie-cutter mold.

Getting ahead at work is often based on how much your boss sees herself in you

A growing body of scientific evidence bears this out.

In their new book, "The Class Ceiling," the sociologists Daniel Laurison and Sam Friedman highlight the importance of sponsorship, i.e. having someone senior advocate for you, when trying to get ahead at work. So far, so sensible. But, the authors observe, sponsorship generally isn't based on work performance. Instead, it comes down to "cultural affinity," such as a similar background or shared interests and hobbies. In fact, several of the executives they spoke with explicitly admitted to supporting people who reminded them of themselves.

The result is that sponsorship "disproportionately favors those from privileged backgrounds," they write. The authors interviewed one partner at an accounting firm who cited drinking as a key bonding activity for him and his sponsee. The partner is quoted saying, "[The sponsee is] very much in my mould. It wasn't difficult taking him out with me, suggesting things for him to do. It's easy for me to pass on the tricks of the trade. He's obviously a practitioner in that drinking mould so it wasn't difficult."

Read more: An ex-Apple recruiter says there's an unexpected dark side to hiring for 'culture fit'

Your chances of landing that plum promotion may come down to something even more superficial: how closely you physically resemble your bosses. An NPR article highlighted the "Good Hair Study," conducted by Perception Institute, which found that white women rated textured hair not only as "less beautiful" but also as "less professional" than smooth hair. Perhaps that's why most powerful women in business have straight, blonde hair.

That's not to say that male managers are the only ones favoring folks who seem familiar. A report from human resources software company Namely indicates that men and women tend to praise coworkers of their own gender more often.

Being biased in favor of people like you is typically unintentional

Social scientists say these tendencies fall under the umbrella of "similarity bias," or the tendency to favor people who are in some way similar to you over people who aren't.

Sarah Greenberg, lead coach and program design lead at digital coaching platform BetterUp, put it this way: Anytime someone is considering a new hire or a promotion, they're assessing whether they can trust the person with the job and whether the person is competent. When it comes to trustworthiness in particular, we're often looking - consciously or not - for those who are similar to us. So, if someone can demonstrate that they'd excel at the job but seem to have nothing in common with you, it's likely you might not believe that they will succeed.

Greenberg emphasized that this type of bias is a fundamentally human tendency, and is typically unintentional. That is to say, you're not a bad person because you're predisposed to support people like you. But for the sake of your success and the organization's, it's crucial to learn to stop and reexamine these thoughts: Is Sara really more qualified for the job because she and I share a love for tennis?

Some executives are more intentional than others about trying to override their unconscious biases. Lisa Borders, who was president of the Women's National Basketball Association, told The New York Times that she prioritizes diversity in her recruits. "I'm always looking for the opposite of what I am, for the most part," Borders said. Instead of looking for a "duplicate" of herself, she said, "I am often looking for the person who can complement the skills I already have."

Fostering diversity in leadership needs to start with a deliberate recruiting strategy

Still, the moment when a spot opens up in the C-suite isn't the ideal time to start scrambling for someone "different" to fill it.

Jaime Klein, founder of Inspire Human Resources, said the strongest companies create a diversity strategy that starts with the recruiting process, and addresses the "pipeline" of employees working their way up through the ranks. That way, when a seat does open up at the executive leadership table, there's already a diverse pool of senior employees to choose from.

But perhaps the biggest mistake we can make is assuming that managers' behavior is a sign of malicious intent. Greenberg said that this typically backfires: "People go on the defensive and they're more likely to double down on these biases."

It comes down to being patient - with others, for sure, but also with yourself. As Greenberg put it, "There's a lot to say about the value of listening to our guts and trusting our inner voice and [knowing] that same inner voice can also be indicative of an unconscious bias."