From Beyoncé Knowles to President Obama, it seems everyone is bemoaning the gender pay gap. Over and over, we hear how greater responsibility for childcare and failure to 'lean in' can cause women to fall behind their male counterparts at work. However, my research suggests there's a new culprit behind the pay gap – this time, organizations may be to blame.

I call the problem the "sex partition", and here's an example of how it plays out at work. A senior executive, let's call him Ben, has an extra ticket to tonight's Yankees baseball game. Two junior employees, Anita and Allen, are both free this evening. No surprise, Ben asks Allen to join him at the game. Why choose Allen? Because inviting Anita is complicated. She might think Ben is hitting on her, or since Ben is a senior executive, she might even see it as sexual harassment. And, what about other employees – what would they think if word got out that Ben took Anita to a baseball game? It's not worth the risk. Over hot dogs and beer, Ben provides Allen a tip on how to deal with a difficult client that helps Allen gain a higher profile within the firm. A mentor relationship develops, and Ben continues to provide Allen with valuable advice and information.

Taboos on workplace romance and increased awareness of sexual harassment issues have left some employees confused about how to interact with opposite sex coworkers, and it has become easier to limit socializing, both inside and outside the office, to coworkers of the same sex. The barriers between male and female coworkers that are a result of organizational policies on office relationships and sexual harassment make up what I call the sex partition.

The sex partition limits the number of friends everyone has at work, and research clearly indicates that better networks result in bigger paychecks and faster promotions. So, if the sex partition limits everyone's friends, why is this a women's issue? Since men still typically run most corporations, the most valuable friends and mentors are men. Due to the sex partition, senior male employees prefer to stick with other men when it comes time for dinners, drinks, late-night meetings or business trips. When it's time for promotions or pay raises, these same executives are more likely to show preference to the employees with whom they feel most comfortable – other men.

Not all employees fall prey to the sex partition, but one study (pdf) reports that 64% of senior executive men are reluctant to have a one-on-one meeting with a junior woman at work. If women can't even get a meeting with a senior executive, how are they supposed to find mentors or establish networks that are critical for career success?

Organizational policies, of course, are not the only contributor to women's difficulty networking with men. Our preference for same-sex friends starts at a young age, when girls and boys develop different play styles and unique interests. These too, can translate into a preference for same-sex friends as adults.

All hope is not lost. An important step in breaking down the sex partition is raising employees' awareness of these issues. Employees must understand the impact of limiting their social networks at work. It's unlikely it ever occurred to Ben that his preference for same-sex baseball buddies would have career repercussions for women in his firm. However, once aware of the sex partition, he may be more likely to invite a female employee to join him next time.

Since employees' strong reaction to workplace policies contributes to the sex partition, accuracy in communicating these policies is also key in breaking down the partition. Occasionally, enforcers of these policies, in their efforts to limit legal liability, can overstate what constitutes harassment. This only adds to the confusion and anxiety in dealing with opposite sex coworkers. One male employee I spoke with was reprimanded by his human resources department for complimenting a female coworker on her business suit, and another was lectured for inviting a female colleague to join him for lunch. In addition to accurately communicating what constitutes harassing behavior, we must educate employees about what is not considered harassing behavior. We absolutely don't want employees to sexually harass, but we also don't want employees afraid to compliment opposite sex coworkers. Senior male executives shouldn't hesitate to meet with or mentor junior female employees. No eyebrows should be raised if a man grabs lunch with a female colleague. Indeed, organizations should encourage these behaviors. We must tread carefully, implementing change without impacting the progress we've made in reducing harassing behavior in the workplace. The encouragement to socialize with opposite sex employees cannot be misinterpreted as a pass to sexually harass. It will take some effort to find a new balance, but I'm confident we can figure it out. Given how the sex partition is limiting women's careers, it'll be worth the effort.

• This commentary was updated on 7 February 2014 to reflect the author's final edits.