I distinguish between complexity and complicated. I use the word “complexity” to describe a state of the world. The word “complicated” describes a state of mind. The dictionary definition for “complexity” suggests things with many intricate and interrelated parts, which is just how I use the term. The definition for “complicated” includes as a secondary meaning “confusing,” which is what I am concerned with in my definition of that word. I use the word “complex” to describe the state of the world, the tasks we do, and the tools we use to deal with them. I use the word “complicated” or “confused” to describe the psychological state of a person in attempting to understand, use, or interact with something in the world. Princeton University’s WordNet program makes this point by suggesting that “complicated” means “puzzling complexity.”
One of the things in the back of my mind when trying to make sense of the Buxton test was Don Norman's distinction between complicated and complexity, which he laid out in the first chapter of Living with Complexity (PDF).
It's a distinction I've found useful: complexity refers to the state of the world and complicated refers to a state of mind. On first viewing Bill Buxton's presentation on Designing for Ubiquitous Computing, I thought that he might be confusing the two. I'm not so sure now. Thinking about his discussion of the "society of appliances" and its relationship to the society of people, I think he sees the two as inextricably linked. By considering the devices we use, the contexts we use them in and the transitions between them, I think Buxton's intention is to reduce the complexity of the world, rather than just the psychological state of the people using those devices.