Why Your Brain Can’t Multitask


You can’t multitask.

As someone who’s determined to squeeze as much productivity out of every day as possible, that’s hard to hear.

But if you want to get more done, in less time, with fewer mistakes, you need to stop multitasking (at least most of the time). Here’s why.

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Show Notes

Brain Rules by John Medina

In Defense of Multitasking” by David Silverman

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### Transcript

**Armi Legge:** You have just finished a busy day. You were doing something during every spare second and worked on a hundred different projects. You should feel satisfied but you don’t. Instead, you feel like you got nothing done and still have much more to do.

If you’ve ever been in that situation before, think about this question. “Do you consider yourself a great multitasker?” If so, you’re wrong. Your brain can only think about one thing at a time. It can do amazing things like design rockets that fly to the moon and invent cupcakes, but it can only think about one thing at a time.

It can switch between tasks quickly but, as you’ll see, your brain doesn’t work nearly as well when you force it to alternate like this. If you your day involves any level of cognitive ability, decision making, problem solving, or thinking, the information in this podcast will help you get more done with less time and effort.

My name is Armi Legge and you are listening to Impruvism Radio, the podcast that gives you simple, science-based tips to improve your health, fitness, and productivity.

I have another announcement for you today. I’m getting much closer to launching Chef Labs. My tentative launch date is September 16th. That’s a little later than I wanted to launch but I’ve been working hard to give you some of the best recipes, so please forgive me.

In case you haven’t heard about Chef Labs on previous podcasts, it’s a new website I’m building to help you become independent in the kitchen so that, if you want to, you can cook all of the meals for yourself and others. You will also learn a lot about the science and why behind different cooking methods and ingredients.

One of the other cool things that makes Chef Labs different is that you’re going to have the opportunity to be part of the research team. I’m going to choose a group of people who will help me develop, test, and refine recipes. You’ll get recipes long before they ever appear on the site and will be directly involved with the final product.

You will learn more details about the Chef Labs research team and how to sign up next week. If you have a recipe that you would like to be published on Chef Labs, you will also be able to submit your ideas on the site. You will also obviously get full credit for your work.

If you like what you hear on today’s show, here is how to get more like it. Go to www.impruvism.com. Enter your email address in the box on the right side of the page and click the button below. After you do, you will get free updates from the Impruvism blog delivered to your email inbox when they are published.

I’ve been reading an excellent book called “Brain Rules” by John Medina, a developmental molecular biologist and the director for the Brain Center for Applied Learning at Seattle Pacific University. In the book, he describes how complex the brain is and how we’re just beginning to scratch the surface of how it works.

Medina takes a very science-based approach, just like Impruvism, and he doesn’t take any claim lightly. In “Brain Rules,” he lays out 12 of the most scientifically supported principles for how the brain works and gives practical tips for how to implement these facts.

His first rule is that exercise is good for the brain and I’ll probably have to do a podcast on that as well. However, today, we’re talking about his fourth brain rule where he talks about why multitasking is impossible.

This is true because your brain can only think about one thing at a time. It can control automatic processes like heart rate, breathing, digestion, and body temperature without any conscious effort, so those functions don’t really count. However, you can only place your conscious attention on one task at a time.

Your brain can transition between tasks quickly, which is what everyone does when they’re multitasking. The problem is that transitioning between tasks like this decreases your mental performance and productivity. When you transition between tasks repeatedly, you take longer to complete tasks, you make more mistakes, and you have trouble refocusing on important tasks when you are not multitasking.

As one 2010 review study from Ghent University in Belgium put it, “Switching to a new task results in a slower and more error prone execution of the task.”

Driving is a good example of the dangers of multitasking. A study in 1997 found that while you are taking on your cellphone, your risk of having a car crash is 400% greater. Nothing earth-shattering there.

Here is another great study to illustrate how detrimental multitasking can be to your focus. In this study, researchers looked at how people using hands-free cellphones like Bluetooth devices were able to focus while driving. They found that even though the people were actively paying attention to their surroundings, they still weren’t really picking up on important features. Even though their eyes were focused on the road and their environment, their brains were still talking to the person on the other phone. They repeatedly missed important features of their environment that could cause an accident, like a car running a red light. To quote the researchers, even when participants are directing their gaze at objects in the driving environment, they may fail to “see them when they are on the phone because attention is directed elsewhere.”

For the record, I admit that I am as guilty as anyone of distracted driving. I don’t usually talk on the phone, but I sometimes text and I usually listen to music, often changing songs and/or radio channels.

The point is that research has clearly shown that people suck at doing multiple tasks at once. Even when you take breaks between tasks to refocus your attention and prepare for the next task, your performance still suffers. You tend to make more mistakes and take longer to complete the tasks.

Multitasking costs you time and productivity for two reasons: switching costs and mixing costs.

Switching costs are the time and performance losses that you suffer for moving between different tasks. This is what happens when you go from reading a book to checking facebook and can’t find your place on the page.

Mixing costs are the time and performance losses your brain suffers when trying to suppress thoughts of your previous task while simultaneously refocusing on your current task. This is what happens when you’re trying to read your book again after checking facebook but you can’t get that meme your friend shared of Miley Cyrus out of your head.

Researchers now think that mixing costs are likely the main problem with multitasking. On simple or easy jobs, it often only takes around 200 to 300 milliseconds to move between tasks. Even when it takes longer than that, the overall amount of time for switching tasks is still minimal. However, the problem is that even though you might have found your place on the page again, you’re still thinking about Miley Cyrus. Your brain is still focused on your last task.

When you’re working on solving a problem, your brain becomes better and better at solving that specific problem. By “problem,” I mean any project, whether it’s writing an article, giving a speech, reading a book, or driving your car. Basically, you get into a flow or groove or zone where it becomes easier and easier to maintain or improve your performance on that problem. Research calls this “task set inertia.” Achieving this kind of inertia takes time and practice, both over the long term and each time you get into this “zone.”

When you break this mental inertia, it’s much harder to get back into it. However, here is the part you probably didn’t know. When you break this mental inertia to check facebook or what have you, you can’t completely get out of this zone, at least all the time. Studies have shown that even hours after being interrupted from a series of tasks, people were still distracted from their current assignments. They couldn’t stop thinking about their previous work and trying to suppress those thoughts made it even harder to focus.

The total amount of time and productivity you lose from multitasking depends on five factors:

1. How familiar you are with the task.

2. How challenging the task is to you.

3. The environment in which you’re trying to complete the task.

4. Your mental state.

5. Whether or not you have visual or other sensory cues to help you switch between tasks.

When you switch from more familiar tasks to less familiar ones, your brain takes even longer to focus. When you switch from less familiar tasks to more familiar tasks, you have an easier time transitioning.

Here is a good example. I am not good at dancing but I am pretty good at cooking. If you have to go from cooking to dancing, it is going to take a lot more mental effort to refocus and forget about my cooking. If I go from dancing to cooking, it is much easier to refocus and forget about dancing.

If the task or tasks you’re transitioning between are more challenging, then you take more time to refocus, lose more productivity, and generally make more mistakes. Another example:

Statistics and Spanish are both hard for me so transitioning between them is much harder than transitioning between listening and singing along to Carly Rae Jepson and Taylor Swift, which is very easy because they’re both amazing. With the former, I’m going to make far more mistakes and take more time to refocus. With the latter, I will probably hit every lyric.

Your environment also impacts your ability to transition between tasks. If you’re working in a busy office cubicle with a printers, fax machines, annoying coworkers, ringing telephones, extremely bright lighting, and other distractions, it’s much harder to switch between tasks or focus on anything. If you’re in a more peaceful and less distracting environment, switching tasks is much easier.

If you’re anxious or angry, you do an even worse job of switching tasks. This is ironic since often we try to multitask when we’re feeling overwhelmed or anxious, which is the worst time to do so.

Finally, your external cues can make a big difference in your ability to multitask. If you have a timer or alarm telling you it’s time to switch tasks, it’s much easier to refocus. If you switch tasks based on feel or when you get frustrated with a task, it’s harder to make those transitions.

In general, these factors are additive. If you’re trying to complete a task that is unfamiliar and challenging in a distracting work environment while you’re nervous or feel overwhelmed and without visual or auditory reminders about when to switch, you’re not going to get much done.

At this point, you might be thinking that multitasking is always bad and you should never try to do more than one task at a time. However, as is often the case, it’s not that black and white. There are some instances where multitasking might be advantageous.

David Silverman of the Harvard Business Review wrote an article with some great points for why multitasking can be a good thing. I’ll quote his major points below and offer some explanations and examples:

First, multitasking helps us get and give critical information faster. In many cases, you can get work done much faster if you can communicate with others more frequently.

For instance, when I’m working on designing Impruver, the app that makes tracking your fitness easy, there are a lot of times when Daniel has a question about something or I have a question for Daniel that might take an hour of work to complete. If we can ask each other questions quickly about the issues, we might figure out a simple way to do it, or that the is unnecessary, thus saving a lot of time.

Second, It keeps others from being held up. In the same vein, there are many times when you need to get or give information from or to others. If you have to wait several days to get permission before starting something, whatever it is you’re working on is going to take much longer.

For instance, when I’m working with personal training clients, I try to respond to messages about workouts and nutritional concerns as fast as possible. Often, the person isn’t sure how they should proceed until they get my advice, though obviously the goal is to get them to the point where they don’t need it.

Third, it gives you something to turn to when you’re stuck. There are a lot of times when you need to grind through a tough project and get it done. Other times, you need a break.

For instance, on Wednesday, I was not in the right state of mind to write a podcast outline. Instead, I worked on developing and testing some recipes, taking food pictures, and doing a few more things to get ready for launching Chef Labs. In some cases, it’s better to just take a break and do a different task.

Fourth, the higher up you are in the organization, the more important multitasking is. I would slightly modify this to say that the higher your responsibility level, the more tasks you are trying to complete, and the diversity of those tasks will require more multitasking.

For example, I work as a writer, a podcaster, a nutrition and training consultant, software developer, marketer, social media manager, and soon to be recipe developer and food blogger. I also have a pretty active social life and train for four different sports: swimming, cycling, running, and strength training. These different projects require a lot of different tasks to be completed, so I often have to switch gears more than I’d really like.

Basically, there are times when multitasking and necessary or even beneficial. While you might not perform as well on these tasks, the benefits outweigh the downsides. As Silverman puts it, “You can’t really deny that in our day and age, some multitasking is inevitable.” However, it’s important that you do it correctly and in the right context. Here are the main points from this podcast:

1. Your brain can only focus on one conscious thought or action at a time.

2. When you keep switching tasks, your problem solving, decision making, and general thinking ability decrease. You take more time to complete tasks. You make more mistakes. You have a harder time focusing on your project. If you’re doing something important, focus on that and only that until you are finished.

In the next podcast, you learn how to avoid multitasking, how to decide when it’s appropriate to multitask, and what science have shown to minimize the negative effects of multitasking.

To find links to everything we talked about in today’s show, you can go to impruvism.com/multitasking-myth-podcast. You can also find links to all the studies mentioned on this podcast on the same page.

If you enjoyed this podcast, the best way to show your appreciation is to leave a positive review and ranking on iTunes. To do so, navigate to impruvism.com/itunes, and you will be redirected to where you can leave your comments. You can also search google for “Impruvism Radio” and find the same page. Thank you for listening and I will see you next week.

### References

1. Strayer DL, Cooper JM, Drews FA. WHAT DO DRIVERS FAIL TO SEE WHEN CONVERSING ON A CELL PHONE? PROCEEDINGS of the HUMAN FACTORS AND ERGONOMICS SOCIETY 48th ANNUAL MEETING—2004. 2004:2213–2217. Available at: https://www.psych.utah.edu/AppliedCognitionLab/HFES2004-000804-1.pdf.

2. Derakshan N, Smyth S, Eysenck MW. Effects of state anxiety on performance using a task-switching paradigm: an investigation of attentional control theory. Psychon Bull Rev. 2009;16(6):1112–1117. doi:10.3758/PBR.16.6.1112.

3. Braver TS, Reynolds JR, Donaldson DI. Neural mechanisms of transient and sustained cognitive control during task switching. Neuron. 2003;39(4):713–726. Available at: https://ccpweb.wustl.edu/pdfs/2003Neuron713-726.pdf.

4. Ramsey NF, Jansma JM, Jager G, Van Raalten T, Kahn RS. Neurophysiological factors in human information processing capacity. Brain. 2004;127(Pt 3):517–525. Available at: https://brain.oxfordjournals.org/content/127/3/517.

5. Yeung N, Nystrom LE, Aronson JA, Cohen JD. Between-task competition and cognitive control in task switching. J Neurosci. 2006;26(5):1429–1438. doi:10.1523/JNEUROSCI.3109-05.2006.

6. Redelmeier DA, Tibshirani RJ. Association between cellular-telephone calls and motor vehicle collisions. N Engl J Med. 1997;336(7):453–458. doi:10.1056/NEJM199702133360701.

7. Wylie G, Allport A. Task switching and the measurement of “switch costs”. Psychol Res. 2000;63(3-4):212–233.

8. Murray MM, De Santis L, Thut G, Wylie GR. The costs of crossing paths and switching tasks between audition and vision. Brain Cogn. 2009;69(1):47–55. doi:10.1016/j.bandc.2008.05.004.

9. Eysenck MW, Derakshan N, Santos R, Calvo MG. Anxiety and cognitive performance: attentional control theory. Emotion. 2007;7(2):336–353. doi:10.1037/1528-3542.7.2.336.

10. Rubinstein JS, Meyer DE, Evans JE. Executive control of cognitive processes in task switching. J Exp Psychol Hum Percept Perform. 2001;27(4):763–797.

11. Wager TD, Jonides J, Smith EE. Individual differences in multiple types of shifting attention. Mem Cognit. 2006;34(8):1730–1743.

12. Arrington CM, Altmann EM, Carr TH. Tasks of a feather flock together: similarity effects in task switching. Mem Cognit. 2003;31(5):781–789.

13. Vandierendonck A, Liefooghe B, Verbruggen F. Task switching: interplay of reconfiguration and interference control. Psychol Bull. 2010;136(4):601–626. doi:10.1037/a0019791.

14. Kiesel A, Steinhauser M, Wendt M, et al. Control and interference in task switching–a review. Psychol Bull. 2010;136(5):849–874. doi:10.1037/a0019842.

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