How can the knowledge of human memory inform the design of better user interfaces?

In UI design, keep in mind that the human mind can grasp at most 6 or 7 distinct "items". This is known as Miller's law. This implies that if you need to present more information, cluster them such that the mind can drill down into one of the "compound" items, or create separate pages. This is also why "wizard" type UI's tend to work well.