To make it short: Humans are not good at multitasking.

Yet, knowledge workers in Corporate America are being asked to do exactly that. They are being expected to stay on top of incoming email exceeding easily hundred, in some cases hundreds a day. They are being asked to be reachable, go to meetings and handle multiple assignments with ease.  Multitasking is seen as a virtue. The ability to do so receives praise. However, multitasking comes at a significant cost.

In my work with knowledge workers, I find many examples that show that our brains cannot fully focus when we multitask. People take longer to complete tasks and are predisposed to error. When we attempt to complete many tasks at one time, or rapidly shift between them, errors go way up and it takes far longer. It takes more time to get the jobs done than if the tasks were done sequentially. This is largely because the brain is forced to restart and refocus. A study found that in the interim between each exchange, the brain makes no progress whatsoever. Therefore, multitasking people not only perform each task less suitabe, but lose time in the process.

Even computers are not good at multitasking as we find out when we open too many applications and windows on our desktop machines. Our system slows down and sometimes comes even to a stop. We need to reboot then. In computer science speak this effect is called “thrashing”. Our computers use hard-drives as extended memories. If they cannot hold enough data in their memories they push them out to disk. If you have enough applications running in parallel the system performance is reduced because files have to be swapped from the computer memory to the hard-disk back and forth. You can bring any computer system to its knees by increasing the number of parallel processes.

A similar thing happens with the human brain. Let’s say we write a document (task 1) and get interrupted by a phone call (task 2). 

1. Writing a document requires focus. Blood rushes to the anterior prefrontal cortex – the switchboard of our brain. It basically activates the brain region required to perform the task at hand.
2. Then there is the identification of the neurons within this region capable of completing the task as well as the triggering of the actual task processing itself. This process is called “rule activation” and takes several tenths of a second to accomplish. We begin to write.
3. While we are typing, our sensory system picks up the ring tone of our cell phone. Speaking and engaging in conversation are handled by a different brain region. Via the anterior prefrontal cortex the process of disengaging from our writing task is managed. We store enough information to resume this task later. Then, the new task 2 is started (see steps 1 and 2).
4. We start another rule activation for task 2. We have real measurable switching costs.

These are the steps that occur between two tasks. Imagine to what extent we are taxed with switching costs in a work environment, where we process daily hundreds of emails, tens of calls and deal with multiple project assignments. Anything that can be done to bring focus in the work day, anything that can be done to bring hours of uninterrupted work time will enhance productivity.

I have found in my work with corporate clients that people who are regularly interrupted take up to fifty percent (50%) longer to finish their tasks. Also, the amount of errors goes up about that much. There are very effective excercises to demonstrate this effect. Keep that in mind when you organize your day.