Engaged, enthusiastic, and loyal employees are pivotal drivers of growth and health in any organization. The key to creating such workers in your business is as simple and cost-free as it is overlooked. It comes in the form of giving them what they want, need, and deserve more than anything else: to be known.

Yes, known. And not in some esoteric sense. Known in the way that all people want to be known, by friends and family. Who they are. Where they come from. What makes them tick. How their life is going.

When employees feel anonymous in the eyes of their managers, they simply cannot love their work, no matter how much money they make or how wonderful their jobs seem to be. But when they are known, they work harder, promote the company enthusiastically, recruit other good people to the organization, and make greater sacrifices for customers. All of which is more effective than any PR or marketing campaign will ever be.

Consider the practical approach a top executive at one of America's largest, most successful companies takes to ensure that his organization hires managers who will be actively interested in the lives of the people they lead. When he interviews managerial candidates, he asks about the largest number of direct reports they've led. Assuming he wants to understand their potential span of control, the interviewees often proudly explain that they've bossed 15 or 20 people. The executive then asks them to list those employees by name. If they hesitate and make excuses for not remembering, they're on thin ice.

Next, the executive chooses one of the people from the list and says to the interviewee, "OK, let's take Harriet. Tell me what was going on in Harriet's life while you were managing her." If the interviewee stammers and provides some generic answer, that thin ice breaks. In this executive's company, knowing employees is an inviolable requirement for all managers.

I got a hard-hitting reminder about how rare it is that managers truly care about their workers after I'd spent a few days with a pro football team at its preseason training camp. I was shocked by the relatively dour attitude of the players, who I thought would be giddy with joy given that they make so much money playing a child's game for only part of the year--then I figured out why they weren't.

The team had just traded for a famous, wildly talented, but troubled young player. So I asked the coach, "Are you going to have this guy over to dinner to get to know him and find out about his challenges and what makes him tick?" The coach, a very nice person, looked at me like I was a little crazy and said, "Pat, this isn't college or high school. It's professional football. We don't do that. This is a job." No wonder so many pro athletes are miserable, and so destructive off the field.

When leaders throughout an organization take an active, genuine interest in the people they manage, when they invest real time to understand employees at a fundamental level, they create a climate for greater morale, loyalty, and, yes, growth. If you doubt this, talk to someone at Southwest Airlines, Chick-fil-A, or the San Antonio Spurs. But don't ask one of the executives; ask an employee. You'll be told that the boss, and probably the boss's boss, knows about his or her passion for cycling or talent in woodworking or child with diabetes.

What exactly is the ROI of this? All the MBAs on Wall Street couldn't justify it on a spreadsheet. But that doesn't stop the best companies from doing it anyway.

From the September 2015 issue of Inc. magazine
The opinions expressed here by Inc.com columnists are their own, not those of Inc.com.