The process of taking information out of your mind and placing it into the environment is known as a cognitive artifact and expands our capacity to think because we've removed some of the information and created more space (brain power) to think about new tasks.

When you use cognitive artifacts, your brain understands and accepts that you won't forget things and releases them from consciousness. Later, going through the piles reminds us of their intent, thus reinforcing the extension of our working memory. 

Think of it like this:  When someone ties a string bow around their finger to remind themselves of something, the bow is a cognitive artifact.  When we look at the bow, we remember whatever it is intended to represent.  So in this metaphor, bow = messy desk piles; looking at the bow = remembering tasks we still need to do.

When it comes to our desks, all of us have different working styles.  Some people make piles, some use folders, some create lists, some stack from left to right while others from right to left or top to bottom.  Still other people have desks that appear to have no organization whatsoever and yet, they know exactly where everything is.  Those piles (however we create them) act as triggers to remind us what needs to be done.

The logical conclusion then is this:  People who have messy desks are able to multi-task more effectively and are more likely to accomplish far more tasks than someone who works linearly (i.e. one task at a time) and cleans their desk completely every day.

[Insert rejoicing, horns blowing, confetti falling and 'o happy day' for the messy desk owners!]

While extending our working memory via cognitive artifacts is a great way to multi-task, we should use care not to keep clutter on our desks for no good reason other than we simply can't bear to discard it.  As it turns out there are studies that indicate we don't use 60% of the things on our desk or 80% of the things we file.  So do your best to restrict your piles to those things that truly reflect necessary and productive work.

Unnecessary clutter not only takes up physical space, but it can totally overwhelm your mental space which ultimately leads to stress.  So get yourself organized, stop feeling guilty about having a messy desk and try not to be freaked out by the concept that a full desk is a reflection of what's going on in your mind. 

Benjamin Franklin once said 'A place for everything, everything in its place'.  He just didn't say it had to be neat or tidy.