"Doing several things at once is a trick we play on ourselves, thinking we're getting more done. In reality, our productivity goes down by as much as 40%. We don't actually multitask. We switch-task, rapidly shifting from one thing to another, interrupting ourselves unproductively, and losing time in the process".

Peter Bregman, en Harvard Business Review Blogs, (http://blogs.hbr.org/bregman/2010/05/how-and-why-to-stop-multitaski.html)