I'm mining Interface Mafia's site for the great articles there. The first article is Part I of a series of articles by Kevin O'Boyle "intended to introduce some of the basic scientific and engineering concepts that lie at the heart of good human interface design". This article discusses chunking. Chunking is how your brain deals with complexity. It turns out that we humans can’t really handle much information at a given time; If you are a genius or an idiot, your working memory (the hip modern name for “short term memory”) can retain, at most, only about 7±2 things at one time. “Wait a minute!” you’re saying, “I deal with a lot more complicated things than that!!!” Well, you do and you don’t: When we are confronted with more than 7±2 things to think about we try to group some of them into “chunks” and tune the others out until we are again dealing with at most 7±2 things. The price we pay for chunking is we can only operate consciously on one level of chunking at a time. In other words: If I look into the contents of a chunk then my mind loses track of the other chunks at the same level as the chunk I am examining.