In today’s world, where we are inundated with information from various sources every few seconds and bombarded by constant connectivity, people place great importance on the ability to multitask.

We talk on the phone while driving, text during dinner, or watch a movie while checking email. We get asked with ever more frequency about the ability of people to multitask, or to do at least two things at once.

The human brain, specifically the cerebral cortex where cognitive function takes place, is oriented to complete singular tasks. Evolution has developed in us the ability to focus on a single task for a long period of time, probably to perform complicated tasks like building a fire, hunting for food, or eluding a dangerous situation. And despite all those selection pressures having now disappeared, we are stuck with a cerebral cortex that can concentrate on only one … thing … at … a … time. Although we may wish otherwise, it’s a fact that almost no one can multitask, especially when the tasks require us to pay attention.

But we still try. Even taking into consideration the limitations of our physiology, we are inundated by more stimuli than ever before, and our cognitive brains must process all of this stimuli, prioritize it, and then act on the one stimulus that is most important to our lives in that moment. The only multitasking we can successfully perform involves tasks that are part of rote learning, or retrospective memory, over and over again without needing concentration. In fact, this should be the true definition of multitasking: The ability to do one thing without cognitive thought while doing another that requires cognitive thought.

I love to do the dishes while on the phone, as washing dishes is a rote task that requires no concentrated thought, no need for the cerebral cortex to get involved. I do sometimes find an unwashed pan in the morning, but it’s a small price to pay for talking with my sweetheart while doing the dishes.

The reality is, none of us can multitask. But we would all like to think we can.

When we try to perform two tasks that require cognitive thought at the same time, our cerebral cortex will demote one of those tasks to a lower section of the brain, one of memory and past learning. So, when we try to perform two cognitive tasks at once, both will suffer a lack of concentration. Some people try to multitask by shifting their focus from one task to another, over and over again, giving full attention to one task for a minute, then to the other, then to the other, etc. The result is the same: Demotion of any task from cognitive thought to rote memory hinders performance, and doesn’t allow us to do either task well.

Understanding the way people interact with their surroundings is the key to great Experience Design. Not only is it important to understand that people can’t multitask, but it’s also important to recognize that most people think that they can. Our job as Experience Design professionals is to design product that meets both of these realities. The iPhone has only one button for good reason: One button addresses the limitations of cognitive thought, while pressing it makes us believe we are multitasking.