At work, 11 percent of us write our to-do lists during meetings, and more than half of us check email while we're on a phone call. Many of us like to think of ourselves as expert multitaskers — and we consider performing two or more tasks at the same time, performing two or more tasks quickly back to back, or switching rapidly between two tasks to be the norm. Yet what you might not realize is that such alleged productivity isn't all it's cracked up to be. Although many of us are proud of our multitasking abilities, and despite our fondness for juggling multiple cognitive tasks simultaneously, the brain isn't actually built to multitask [source: Faw, Sollisch].
Give the brain one task, and it's no problem. Two tasks, and the brain divides and conquers them. More than two tasks, though, and things change. With divided focus and attention, the brain begins to perform less effectively, and is prone to making more errors.
The human brain, it turns out, doesn't have infinite resources, and it handles tasks sequentially — yet it's able to switch from task to task so rapidly we think we're multitasking. And because we have a limited capacity when it comes to focus and attention, especially when we're concentrating hard, the brain has to choose what information gets processed and encoded. For example, your brain can handle either visual driving-related tasks (looking for an address) or rocking out. Not only is the brain incapable of multitasking, when we try to multitask each goal competes for the brain's available resources. Multitasking creates a traffic jam, and in the end we perform poorly on each task as a result. We overlook important information, we make errors, and we end up remembering less information overall. When the brain is forced to switch rapidly from task to task it doesn't perform as well as it does when it can focus on one thing at a time. Multitasking increases our error rate by as much as 50 percent. And it doesn't speed things up, either — trying to multitask doubles the amount of time it takes to perform each of the tasks at hand [source: Parrish]. When you introduce a third task, the brain's prefrontal cortex, which makes executive decisions, will discard the one it considers the least important [source: Telis]. It's got to do with the limits of our sensory system; we tune out what our brain determines to be of lesser importance. When we're lost or when we have to perform a driving task that we don't do very often, such as parallel parking, we edit our environment. We stop listening to passenger conversation, our field of vision shrinks, and we turn down the radio's volume (or we turn it off) in an effort to throw all of our focus into vision or spatial relationships, respectively.