Jeff Atwood has a great post on the cost of context-switching between projects. The results are amazing. There is a huge productivity loss by juggling more than one thing at a time. I can personally identify with the quality loss when trying to "do homework while watching a movie" or "browse the web while on a phone call". What would be more facinating to evaluate is just what this study shows, the loss of productivity while switching between on-the-job focusses.