Multitasking more often hinders us in our busy lives. Beyond mindless activities, simultaneously attempting 2+ tasks, that need our attention, results in longer completion times & higher error rates. How often have you typed what you wanted to say, or said what you wanted to type when talking on the phone whilst penning an email?
When we multitask, we switch our attention between tasks rapidly & frequently; focus our attention on the first task (e.g. talk), switch tasks, focus on the second task (e.g. type), switch back. If we concentrated on each task in turn we do two tasks; talk & type. By multitasking we attempt three tasks: talk, type & switch. This third task requires its own effort & time, hence more time to complete the original tasks. As we switch between tasks, we must keep track of where we are in task 1, pick up task 2 where we left off. Being human, our task tracking capability is imperfect. The more times we switch the more likely we are to lose track & make a mistake
Test the theory. With a partner to observe you complete these two simple tasks at once: count down from 20 out loud & write out the alphabet. Then repeat, doing the tasks one at a time. Which way is easier, which way is quicker?