The Science of Multitasking

In a world where our to-do lists never seem to get shorter, we are constantly thinking about all the things we need to get done, and how to get them done as quickly and efficiently as possible. Whether it’s answering an email while on a Zoom call or packing lunch for the kids while scheduling a dentist appointment, multitasking has historically been a way to get more done in what little time it feels like we have in the day.

But, is multitasking really helping us live up to our full potential, or is it actually killing our productivity and focus?

What Actually IS Multitasking?

Multitasking is most commonly defined as “undertaking multiple tasks at the same time.” <1> That said, most scientists who study human cognition and behavior agree there are up to three different types of multitasking, and all present similar disadvantages for productivity and focus:

Performing two tasks simultaneously.
This is what usually comes to mind: talking on the phone while driving, answering emails during a meeting, or texting while walking.

Switching from one task to another without completing the first task.
We’ve all been there—you’re finally in the zone on an important project when a coworker stops by for a chat.

Performing two or more tasks in rapid succession.
Our brains need time to switch gears to work efficiently and avoid errors. Jumping on an important call immediately after meeting with your supervisor can impair productivity and focus.

When it comes to any type of multitasking, many of us like to think we’re pretty good at it. In the age of “hustle culture,” multitasking is often labeled as a valuable skill; the more you can do at one time, the more efficient, hardworking, and capable you are. However, it is estimated that only 2% of the population is actually able to multitask efficiently. <2> For the other 98% of us, a growing body of research shows it’s far less efficient to try to do two (or more) things at once. What’s more, multitasking is taking a toll on our mental and physical health.

What Happens When We Multitask?

To understand why multitasking doesn’t really work—and why it can be harmful—we need to understand what happens to our brains when we juggle too many things simultaneously. According to Kevin Paul Madore, a neuroscientist at Stanford University, when we multitask, we create interference between several brain networks that handle attention and cognitive control. These networks start talking over each other and pulling your mind in different directions, which can lead to delays and mistakes when completing a task. <3> Plus, according to neuropsychologist Cynthia Kubu, PhD, even when we think we’re multitasking, most often we aren’t actually doing two things at once. Instead, we’re doing individual actions in rapid succession—also known as task switching. <4>

Research summarized in the Encyclopedia of Neuroscience shows task switching requires high cognitive processing, ultimately leading to slower and more error-prone performance. <5>

How Does Multitasking Make Us Less Efficient?

To better understand the inefficiency of multitasking, scientists have examined switch costs, or the time lost when task switching. <6> In 2001, Joshua Rubinstein, PhD, Jeffrey Evans, PhD, and David Meyer, PhD conducted four experiments where young adults switched between tasks of varying complexity and familiarity. In all four experiments, participants lost time when switching tasks, no matter how simple or familiar the tasks were. The lost time increased as tasks became more complex. Even small switch costs (sometimes just a few tenths of a second) add up with repeated switching and can cost as much as 40% of someone’s productive time. <7> Bottom line: taking on too much at once isn’t helping you finish your to-do list more efficiently—it may be slowing you down.

How Does Multitasking Impact Our Health and Wellbeing?

While it’s surprising that multitasking doesn’t make us more efficient, it’s even more surprising that it may adversely affect our health. Remember those brain networks? Research shows that interfering with them—by multitasking—can lead to cognitive problems with memory and focus, and even long-term impacts on mental and physical health.

On busy days juggling multiple tasks, assignments, and activities, you don’t give your brain a chance to consolidate important memories, which can lead to forgetfulness. Stanford researchers found that too much multitasking can lead to lapses in memory and that chronic, everyday multitasking is linked to errors in both working memory (holding/using information temporarily) and long-term memory. <8> The same research found that media multitasking (e.g., texting while watching TV, or responding to Slack during a Zoom meeting) can be especially harmful.

Frequent media multitaskers are generally worse at sustaining attention and more prone to mind wandering. Physically and mentally, studies have found multitasking can increase negative emotions such as irritability and impatience, and even lead to chronic stress (raising blood pressure and heart rate), anxiety, and depression. <9> One study showed chronic multitaskers have smaller brain volumes in the cingulate cortex, a region important for regulating emotions and behavior. So while forgetting to switch the laundry may seem trivial, the cumulative effects matter.

The Takeaway…

We now understand why trying to do multiple tasks at once—especially complex tasks—can negatively affect productivity and long-term health and wellbeing. And while dropping a glass while cooking or emailing the wrong recipient isn’t life-or-death, texting while changing lanes on the highway can be. It turns out humans are actually wired to be mono-taskers. So, slow down, take a moment, and focus (some focus hacks here) brain will thank you.