Why Multitasking is a Lie (And How To Do it Right)

Man on his Mobile

Like many of my fellow Gen Y’ers, I always used to think of myself as being an excellent multitasker. During university classes I would keep my laptop out “taking notes”, while really paying half attention to the professor whilst reading / chatting / doing other homework / browsing the internet. At home, I could never JUST sit and watch a TV show (on my computer of course- who uses actual TV’s anymore?) for fear of feeling unproductive. I would sometimes go so far as to read a full book while watching TV, or even try to read one book while listening to a separate audiobook (a fun mental exercise, but extremely difficult).

What I began to notice across all of these different task combinations was that there were often times when I would suddenly realize that I had no idea what the professor had said in the last few minutes, or what had happened on the TV show. I was able to listen / watch while casually browsing, or having even a few different text-based conversations, but as soon as I encountered something that really interested me suddenly my full attention was captured and my multitasking ability went out the window.

I began to do some more serious research to try and find out why this was the case, and, more specifically, did “true multitasking” actually exist, or was it just a function of our brains jumping back and forth between different tasks very quickly.

It turns out that the answer was “a little of both.”

The Neuroscience of Multitasking

The area toward the front of both lobes of the brain that controls attention and serves to coordinate tasks with the other brain systems is called the prefrontal cortex. A study conducted at the Institut National de la Santé et de la Recherche Médicale (INSERM) in Paris in 2009 lead by Dr. Etienne Koechlin asked participants to carry out two different tasks while measuring their brain activity with an fMRI machine. When participants were told that a large reward would be given for the successful completion of one of the tasks, scientists observed that the amount of neural activity increased predominantly in a single side of the prefrontal cortex. When the reward was associated with the other task, the neural activity increased in the other side.

When the study participants were asked to attempt yet a third task, scientists found that the subjects consistently forgot one of the three, and made three times as many errors as compared with when they were only attempting two tasks.

Koechlin explained how these results suggest that when the brain is focused on a single task, both sides operate concurrently, but when it tries to perform two separate activities simultaneously it splits itself and each side then operates independently. But when it comes to three tasks, juggling them all becomes quite difficult due to our only having two frontal lobes. And even with the two tasks, it seems likely that while brain is simultaneously keeping track of both goals, it still switches back and forth between them for active processing.

Another study from the University of California in 2010 analyzed the effects of multitasking on working memory (the ability to manipulate and store information in the mind over short periods of time), specifically focusing on the previously demonstrated reduced multitasking ability in older adults. The study described how, when interrupted mid-task, the brain “disengaged from a memory maintenance network and reallocated attentional resources toward the interrupting stimulus.” This step was performed similarly by younger and older adults. However, it goes on to state that “unlike younger individuals, older adults failed to both disengage from the interruption and reestablish functional connections associated with the disrupted memory network.”

The term commonly used to describe the negative ramifications of these mental gymnastics is “switching cost”, and has been shown to apply even when we are prepared for the new task or stimulus. So far it seems that switching costs can be reduced by foreknowledge, task familiarity, and younger brains, but never totally eliminated.

But if two simultaneous tasks is our limit, and even then we must switch back and forth between the two, then how is it that people are regularly able to do things such as walk, look out for cars, and talk on the phone all at the same time?

The Power of Habit

Koechlin stated that the ease with which we handle multiple tasks depends on how engaged the prefrontal cortex is. Intuitively, this makes a lot of sense. When we are really focused on something, whether it is an engaging book, challenging math problem, or deep conversation, we have a tendency to shut out external stimuli. This can manifest as a loss of awareness of our surroundings or as our forgetting anything else that we were doing that would take conscious thought.

But how much of what we do throughout the day really does require active attention on our part?

In his book The Power of Habbit: Why We Do What We Do in Life and Business, Charles Duhigg goes into fascinating depth about what habits are, how they are formed, and how we can best take advantage of them. One of the key points that he repeats throughout the book is how once something has become a habit, it ceases to require active mental effort and attention. He even talks about a case of someone who had experienced severe brain damage which eliminated the ability to store new memories, but was still able to form new habits and perform them without any conscious awareness of what he was doing. Why? Because habits do not require conscious thought. They totally bypass the prefrontal cortex.

This then can help explain how some of us seem to perform the seemingly impossible task of doing three or more things at once. How do I eat breakfast, watch TV and IM all at the same time? It’s simple really. I have become so accustomed to eating that the mechanics of it take essentially no conscious thought. The IM conversation then is sporadic enough that it is a relatively simple task for me to watch TV and periodically switch my focus to read or respond to something. But if I read a message that really startles me, or have to write a response with a high degree of care placed on the content and wording, then there is a fairly good chance that I will end up having to rewind the TV show to re-watch a portion that I completely tuned out.

The Truth Behind Self-Proclaimed “Multitaskers”

I’m sure we all know people who claim to be great multitaskers. They keep their TV on, are always on their phones, conduct whole meetings in the car, and claim that they are the exception- able to perform all these tasks at peak efficiency. Dr. Clifford Nass, a researcher at Stanford who has been studying this type of people for years, would claim differently.

Nass examined a group of both “high multitaskers” and “low multitaskers” and studied their ability to filter information, switch between tasks, and maintain a high working memory, saying that these are the key components underlying successful multitasking. He theorized that the high multitaskers should perform better in at least one but likely all three of these areas. He turned out to be completely wrong.

We were absolutely shocked. We lost all our bets. It turns out multitaskers are terrible at every aspect of multitasking.” – Nass

But if this is truly the case, and good multitaskers don’t actually exist (or are so rare as to be statistical anomalies), then why is it that so many people continue to believe that they are in fact great at it?

One likely answer can be taken from the research of Zhen Wang, a researcher and assistant professor of communication at Ohio State University. She was able to study a group of students over a period of time, analyzing their daily routines and study habits outside of a laboratory environment. She found that “There’s this myth among some people that multitasking makes them more productive, but they seem to be misperceiving the positive feelings they get from multitasking. They are not being more productive- they just feel more emotionally satisfied from their work.”

When comparing students who studies while watching TV with those who studied without, she found that those who studied with the TV reported feeling more satisfied and productive while simultaneously failing to achieve as great of a success in their cognitive goals.

My Multitasking Workaround

One key point from Koechlin’s study that is glossed over is the fact that both of his tasks involved some type of visual detection. This was doubtless due to the fact that the visual centers in the brain are easy to monitor in an fMRI and it made for cleaner data. However, it is fairly readily apparent that our visual system is really only designed for tracking single objects at a time, therefore attempting to multitask by keeping track of two different visual stimuli can be inherently difficult.

My own extensive experimentation with my multitasking abilities has lead me to the following simple rule:

The larger the number of shared sensory resources between two tasks, the more difficult it will be to perform them simultaneously, with attention capacity being finite across the board.

This is why it is so easy to listen to music while doing almost anything that does not directly require listening to something else. It utilizes the brain’s auditory processing resources and rarely has to fight for them. Additionally, we rarely have to worry about fighting for attention with the music because we are typically raised to prioritize visual stimuli over auditory ones.

Similarly, it is quite easy to give someone a massage whilst simultaneously watching a movie. The massage is both something that is practiced (and therefore largely habit that requires little attention) and also primarily based on touch, leaving the visual and auditory processing resources open for other inputs.

Optimize Your Productivity

What have we learned after all this?

  1. There is no “true” multitasking
  2. For two tasks, it might be possible to hold both in each half of the brain so as to more easily switch back and forth between the two
  3. Even for only two tasks, there are always some switching costs
  4. The more cognitively taxing a task, the harder it is to multitask with it
  5. The closest we come to actual multitasking is when one of the things we are doing is a habit that can be put on autopilot
  6. Multitasking makes us feel more productive while actually hurting productivity
  7. Multitasking is easier when the tasks have minimal sensory overlap

Nowadays the way that I look at it is not “how can I multitask most efficiently,” but rather “how can I make sure that I am utilizing my maximum brain capacity at all times.” The key distinction being that, contrary to popular belief, often the way to succeed at the latter goal is really just to be fully focused on a single task. But if the main task that I am performing does not take significant conscious thought, then I still try and figure out what I could be doing simultaneously so as to maximize my productivity.

Given how visually focused most of us are, the simple question that tends to cover 90% of the cases is just this:

“Could I be just as productive at my current task while listening to an audiobook? If not, what about if I listened to music?”

Note: There is actually a large body of research solely focused on the impact of music on performance for different types of activities. Much of it is based off of these underlying concepts, but I will be covering the specifics in a separate blog post.


Charron S, Koechlin E. Divided representation of concurrent goals in the human frontal lobes. Science. 328(360), 360-363 (2010).

Clapp W, Rubens M, Sabharwal J, Gazzaley A. Deficit in switching between functions underlies the impact of multitasking memory in older adults. Proceedings of the National Academy of Sciences of the United States of America. 108(17), 7212-7217 (2011).

Gopher, D., Armony, L. & Greenspan, Y.  Switching tasks and attention policies. Journal of Experimental Psychology: General, 129, 308-229 (2000).


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