Last week, Harvard Business Review published a very short piece that packed a remarkable punch: “Why You Lead Determines How Well You Lead,” by Tom Kolditz. It condenses a study, “massive in scale, track[ing] more than 10,000 Army leaders from their entrance into West Point, through graduation, and well into their careers. For perspective, the sample represents approximately 20% of the living graduates of West Point.” This is a particularly rich dataset because the annual Army performance appraisals are designed to compare officers’ performance to the Army’s leadership framework and gauge the officer’s potential to lead at a higher level. Not a bad start.

Here’s the key finding:

As one might predict, we found that those with internal, intrinsic motives performed better than those with external, instrumental rationales for their service—a common finding in studies of motivation. We were surprised to find, however, that those with both internal and external rationales proved to be worse  investments as leaders than those with fewer, but predominantly internal, motivations. Adding external motives didn’t make leaders perform better—additional motivations reduced the selection to top leadership by more than 20%. Thus, external motivations, even atop strong internal motivations, were leadership poison.

Backing up for a moment: The difference between “intrinsic” and “extrinsic” motivations is actually pretty easy to determine. Just ask the leader why they’re in it. Answers range from a sense of identity, purpose, and obligation to the people they serve (intrinsic) to career progression and pay (extrinsic) or, perhaps most strongly intrinsic of all, sheer obligation to serve.

One of the longstanding dichotomies in the field of leader development is whether to teach leadership as skills that lead to higher performance (a competency-based model that is relatively easy to metric), or to teach leadership as a complex moral relationship between the leader and the led (a values-based model that is challenging to metric). Our study demonstrates that those who led primarily from values-based motivations, which are inherently internal, outperform those who lead with additional instrumental outcomes and rewards.

The implications of this study for leader development—and practice—are profound.

Perhaps we have, then, at last, something that is true, not obvious, and actually quite powerful, to say about leadership. Only it has nothing to do with style or technique, strategy or circumstance: It all has to do with stewardship and the “Why?”

Let me leave you with this thought experiment.

If you are leading in a firm you did not found—most of you are—think back to the people whose names are on the door. If you did found your firm, think back to your younger self and the early days of that venture. In either case, you will be gazing at people who have a vision of how the world could be different and want to bring others along with them to help fulfill that vision and live it out. People who aren’t risk-averse, aren’t ceaselessly asking, “Who else is doing this?”, and are not remotely in it for themselves. These are people who can look at the hard steel of reality and choose to forge something new out of it. They have no time for congratulatory pride and know that self-aggrandizement tends to end badly.

Think about on those people, or that prior self.

Now: Why are you leading, again?