Let’s say you’re a hiring manager with two resumes for your open assistant manager position sitting in front of you on your desk. Both candidates graduated with a BSRT from a well-respected university. Both have the RRT credential. Both have eight years of job experience at a large teaching hospital.

Your hospital runs job candidates seeking managerial positions through some leadership achievement and leadership potential testing, and job candidate 1 outperformed job candidate 2 on the leadership achievement test. But job candidate 2 did better on the leadership potential test.

One bird in the hand is worth two in the bush, right? So of course you choose job candidate 1, the proven achiever when it comes to leadership.

Not so fast, report researchers from Stanford and Harvard Universities who conducted a series of experiments to see how managers perceive achievement vis-à-vis potential. As it turns out, when all other things about an applicant are equal, they pick potential over achievement nearly all the time.

Of course, people with more potential are often younger as well, so maybe that explains it. Nope. The researchers controlled for age in the study, and thus the final results did not reflect any age bias.

Why do managers inherently pick potential over a proven track record? According to the investigators, who published their findings in the Oct. 2012 edition of the Journal of Personality and Social Psychology, it all comes down to the uncertainty posed by potential.

Unconsciously, uncertainty is just more interesting, and that means the brain will spend more time processing the information about the candidate with potential than the one with proven achievements. All that extra processing, say the investigators, can lead hiring managers to choose the candidate who appears most likely to help his department succeed in the future than the one who already helped a department succeed in the past.

Of course, it is important to note that this bias for potential over achievement only comes into play in cases where all other aspects of the resumes are about the same. In another study that looked at achievement and potential in job candidates where the candidate with more potential had lesser credentials, the candidate who scored more highly in achievement won out.

The take home message for job candidates: spend more time talking about what you could do for the department you’re seeking to join than what you already did for the department you worked for last.After all, the hiring manager is most interested in what you will do for him once you get the job.