In spite of everything, there is a strong case for doing one thing at a time. Here’s how: separate all activities that you do into low- performance activities and high-performance activities.
High-performance activities those that involve judgment, concentrated focus, and active thought. It is OK to do multiple low-performance activities because your productivity is not affected by the presence of a second low-performance activity. This includes reading a book while waiting in line at the grocery store, watching Jim Cramer on Mad Money while working out at the fitness center, and talking to your parents while folding laundry.
Low-performance activities really can be done on autopilot. In contrast, higher-performance activities can be done more quickly and productively when they are worked on in a concentrated approach. The fewer the interruptions, the higher your productivity.