We found, unsurprisingly, that the stronger their internal reasons were to attend West Point, the more likely cadets were to graduate and become commissioned officers. Also unsurprisingly, cadets with internal motives did better in the military (as evidenced by early promotion recommendations) than did those without internal motives and were also more likely to stay in the military after their five years of mandatory service — unless (and this is the surprising part) they also had strong instrumental motives.

Remarkably, cadets with strong internal and strong instrumental motives for attending West Point performed worse on every measure than did those with strong internal motives but weak instrumental ones. They were less likely to graduate, less outstanding as military officers and less committed to staying in the military.

The implications of this finding are significant. Whenever a person performs a task well, there are typically both internal and instrumental consequences. A conscientious student learns (internal) and gets good grades (instrumental). A skilled doctor cures patients (internal) and makes a good living (instrumental). But just because activities can have both internal and instrumental consequences does not mean that the people who thrive in these activities have both internal and instrumental motives.

Our study suggests that efforts should be made to structure activities so that instrumental consequences do not become motives. Helping people focus on the meaning and impact of their work, rather than on, say, the financial returns it will bring, may be the best way to improve not only the quality of their work but also — counterintuitive though it may seem — their financial success.

There is a temptation among educators and instructors to use whatever motivational tools are available to recruit participants or improve performance. If the desire for military excellence and service to country fails to attract all the recruits that the Army needs, then perhaps appeals to “money for college,” “career training” or “seeing the world” will do the job. While this strategy may lure more recruits, it may also yield worse soldiers. Similarly, for students uninterested in learning, financial incentives for good attendance or pizza parties for high performance may prompt them to participate, but it may result in less well-educated students.