From Issue 2 of Ambidextrous magazine, Don Norman on constant partial attention and interruption:

“My take is that we have evolved to become interruptible and distractible. I think of it not as distraction but attention to change. The problem isn’t that we are continually interrupted, but rather that the technology of interruptions has far too much overhead. the overhead is often far more onerous that the content. So let’s make the interruptions have more content – [and] make it easier to resume afterwards.”

The full interview will apparently be on the Ambidextrous site in the near future.