Why employees who aren't the sharpest knives in the drawer -- at least not that anyone can tell -- might do best of all.

By Megan Hustad

FORTUNE -- Would you rather be thoughtless and successful or intelligent and frustrated?

A recent article in the New Scientist addressed the never-ending ignorance-as-bliss debate with the following question: If being intelligent was an evolutionary advantage, "why aren't we all uniformly intelligent?" The obvious, unscientific answer: Probably for the same reasons we aren't uniformly good-looking. But is being smart always to your benefit? Are there instances when stupid works better?

Stupidity can increase efficiency, claims Mats Alvesson, professor of organization studies at Lund University in Sweden. In a Journal of Management Studies article titled "A Stupidity-Based Theory of Organisations" Alvesson and colleague André Spicer explain how what they call "functional stupidity" generally helped get things done. "Critical reflection and shrewdness" were net positives, but when too many clever individuals in an organization raised their hands to suggest alternative courses of action or to ask "disquieting questions about decisions and structures," work slowed.

MORE: Hospital finances are broken. How to fix them.

The study's authors found that stupidity, on the other hand, seemed to have a unifying effect. It boosted productivity. People content in an atmosphere of functional stupidity came to consensus more easily, and with that consensus came greater roll-up-our-sleeves enthusiasm for concentrating on the job.

Superior intelligence often comes with hidden costs. Say you're a person for whom schoolwork was always effortless. You may be more likely to become frustrated when a job doesn't yield readily to effort.

"I often think that having had to work harder for good grades would have taught me much earlier that not everything worth doing comes easily -- and not being immediately good at something doesn't mean that mastery can't come with hard work," says Sara Grace, host of Ferrazzi Greenlight's "Social Capitalist" podcast.

Decreased diligence is only half of it. In some job situations, being smarter, faster, and more rhetorically gifted might also keep you stuck in your current role longer than your peers.

"When you have a lower-level job, being exceptionally good at it is usually a deterrent to getting promoted," says Lilit Marcus, author of Save the Assistants: A Guide for Surviving and Thriving in the Workplace. For example, "when you're such a great assistant that your boss has difficulty functioning without you, it means that he or she will keep you on as an assistant as long as possible and will not consider promoting you out of their service."

MORE: NYU's part-time MBA: Worth the hustle?

This echoes some of the wisdom dispensed in the 1970s bestseller The Peter Principle. Smart people are more likely to imagine they can push their way up an organization. But critical career advancements, as Sheryl Sandberg confesses in Lean In, are often made when a sponsor higher up on the ladder decides to pull you up with them.

Falling flat on your face -- either from stupidity or attempting something you don't do well -- can also quiet your critics, as the author F. Scott Fitzgerald discovered when his play -- the unfortunately titled The Vegetable -- opened to withering reviews. "Ever since he started to write … it has been difficult for us to forgive him his brilliance," Frederic F. Van de Water wrote. "Now that he has written The Vegetable it should be easier."

But one can't in good conscience recommend public failure as a career-builder. After all, there is a major difference between actually being slower on the uptake and acting as if you are a few cards short of a deck. The trick is not to play dumb, exactly, but rather to learn when to assert your superior intelligence and when to hide your light under a bushel. (And mix metaphors.)

In other words, there's being terrifically clever, and there's making sure everyone realizes you're terrifically clever. Those of us who don't feel the urge to make sure everyone in the room understands, at every available opportunity, just how smart we are might do best of all.

For one, it can help you avoid unnecessary confrontation. A New York-based property developer says that instead of constantly arguing with a partner who bi-weekly comes up with impossible schemes, he responds as if he has no objection with the proposed idea whatsoever. So the business partner wants to walk away from a $500,000 project? Sure! Let's do that. Great idea. Then, he says, he quickly pivots into implementing the plan -- asking which four employees they'd need to can, what orders should be cancelled, and so on down the list of implications. Invariably, the partner reconsiders.

By acting as if he was unable to marshal a strong argument against an iffy plan, the developer let his partner maintain a sense of superiority and spared himself the fallout from a potentially long and drawn-out conflict.

If you're not worried about being perceived as a bit slow, you can ask better questions -- better in the sense that they will likely yield more illuminating answers. This is particularly helpful during negotiations. Asking "dumb" questions "draws out more information that the opposing party may not have shared otherwise," says project manager turned travel entrepreneur Jeni James. "There is also basic psychology around people being uncomfortable with silence and therefore, if you just remain quiet, appearing 'slow,' the opposing party will become uncomfortable, trying to fill the silence and talk, revealing details they maybe shouldn't."

MORE: Say it ain't so, Samsung

When discussing Google's radically pared-down look -- just a search bar on an otherwise empty page -- Marissa Mayer explained that its simple interface was a conscious attempt to mimic a Swiss Army knife. "When you see a knife with all 681 functions opened up, you're terrified," Mayer, then Google's (GOOG) product manager, told an interviewer back in 2002. "That's how other sites are -- you're scared to use them. Google has that same level of complexity, but we have a simple and functional interface on it, like the Swiss Army knife closed."

"Functional" is the key word here. Stupid works if you're smart enough to know when not to be.