I don't know the science but know the effects of blanking out when I multi-task. That a pdoc once described a more appropriate definition of multi-tasking is 'how to screw-up multiple things at one time.' He said research has shown that tests done on the frontal lobe for completing tasks show that the mind is better equipped to handle one task at a time to complete them without being thwarted. Practicing mindfulness and focusing on one task is less prone to error and with better success of completion in actually less time, and then doing the next tasks. The same tasks done one right after another take less time than multi-tasking.