Here’s a way to kill your career: Have a messy office.

Here are things that people with messy offices say: My work gets done; I know where everything is; People are too concerned about appearances.

All these things could be true. But here is what is also true: If your desk is a mess you look like you’re totally out of control.

The FBI has known for decades that you can judge someone by their workspace, which is why the FBI has special investigators who visit the offices of criminals. The FBI doesn’t publish their data on this type of investigation, but the University of Texas does. And a study conducted there found that people with messy offices are less efficient, less organized and less imaginative then people with clean desks.

Some of you who are stubborn (and delusional) are saying, “So what? That’s not me.” But even if you are definitely sure that you are as efficient in your messy office as your neighbor is in her clean office, your co-workers don’t see it that way. The study also found that people perceived messy workers to be inefficient, unimaginative workers.

A messy desk undermines your career in subtle ways. If you are the owner of the company, you give the impression that you cannot handle your position and the company is in trouble. If you are in middle management, when someone is giving away a plumb assignment, she does not think of you because you give the impression that it will go into a pile and never come out. Even if you get every project done well, the perception will be that you don’t.

Still not convinced? Would you ever go to work in striped pants and a striped shirt? Why not? You could still do your job. But people would not perceive that you could still do your job, because appearances are powerful, and someone who dresses in a goofy, unconventional way does not inspire confidence. Appearances matter, and the desk in your office is as important as the clothes on your back.

Managers, take note: This study goes both ways. So if you are thinking of promoting someone, you are probably making the wrong decision if the person’s desk is a mess. Either they are in over their head, or they do not care, but either way, they will not instill confidence in the people below them. In most cases, messy desker should be passed up for someone who is neat.

Take a tip from GE, a company known for developing outstanding managers throughout its ranks. GE requires everyone to have a sparkling clean desk each night when they go home. This makes sense – GE attempts to make everyone a potential manager by preventing people from undermining themselves.

Some of you might call this rule draconian. I can hear you now, “A messy desk is an expression of who I am.” This is probably true. I believe that a messy desk is a reflection of what is in someone’s head. But you need a clear head in order to be creative and efficient in ways that make your work a reflection of your best self.

So take some time this month to clean up your office and create an organized system for maintaining cleanliness. If GE refuses to keep messy desks in its ranks, then you should, too. Start with your own, and then take a look at the people who report to you.