How does multitasking affect the human brain?

Almost everyone does several things simultaneously from time to time. Some people cook, read, talk on the phone and watch TV, all at the same time. Many drink a beverage and listen to music while working. And almost everyone knows what it’s like to walk and eat at the same time. But even this relatively simple sort of multitasking doesn’t always work.

Imagine that you are walking from Point A to Point B in a place you’ve never been to before. In a situation like this, navigating the route is just about all our brains can handle. "Where am I? Are there holes or puddles on the footpath? Am I still going the right way?" Staying on course takes up all of your attention. But at some point, you’ll have walked the route a second time, a third time, a 10th time and maybe even a 100th time. Once your brain knows the way, you require less information and need not pay as much attention to performing the task. A couple of landmarks are all you need to avoid mistakes or potential obstacles. Once familiar with the routine, we basically run on auto-pilot. This significantly decreases the brain’s workload, freeing us to take on tasks in addition to walking, such as enjoying an ice cream, making a phone call, or even both. The basic prerequisite for multitasking is that all of the different tasks have to be able to be accomplished without demanding our full attention. However, if one activity takes the upper hand, multitasking mechanisms begin to break down. For instance, if a phone call suddenly turns serious, you’re likely to stop walking and eating. Once the conversation returns to more trivial matters, you will resume passive listening and continue on your way.

Imagine a good friend is telling you a story for the fifth time. In such instances you can listen while doing several things at once. But this time the familiar story suddenly takes an unexpected turn. Your brain reacts immediately and focuses all of its attention on this new stimulus. This reflex can't be shut off. It works automatically and unconsciously, but there are consequences to this. Not only do we neglect everything else that is happening, but within roughly three seconds our short-term memory is reset. This means we’re likely to forget we are also cooking while on the phone. Whoops, now what’s that burning smell?

Psychological studies show that our capacity for multitasking is limited, indicating that humans can juggle about seven things at once, plus simple decisions if not otherwise distracted. The process becomes more difficult in direct correlation to the degree of muscle and movement coordination that is required. In some cases it’s even prohibited to do some things at the same time, such as telephoning while cycling or driving a car. We’re better off focusing all of our attention on tasks like these.