Task switching is “expensive” — There has been a lot of research on task switching. Here’s what we know from the research:

It takes more time to get tasks completed if you switch between them than if you do them one at a time.
You make more errors when you switch than if you do one task at a time.
If the tasks are complex then these time and error penalties increase.
Each task switch might waste only 1/10th of a second, but if you do a lot of switching in a day it can add up to a loss of 40% of your productivity.
Task switching involves several parts of your brain: Brain scans during task switching show activity in four major areas: the pre-frontal cortex is involved in shifting and focusing your attention, and selecting which task to do when. The posterior parietal lobe activates rules for each task you switch to, the anterior cingulate gyrus monitors errors, and the pre-motor cortex is preparing for you to move in some way.
I know it’s popular to think that you are multi-tasking, but the research is clear that people actually can’t multi-task, with one specific exception that I’ll get to in a minute.

One thing at a time — For many years the psychology research has shown that people can only attend to one task at a time. Let me be even more specific. The research shows that people can attend to only one cognitive task at a time. You can only be thinking about one thing at a time. You can only be conducting one mental activity at a time. So you can be talking or you can be reading. You can be reading or you can be typing. You can be listening or you can be reading. One thing at a time.

We fool ourselves — We are pretty good at switching back and forth quickly, so we THINK we are actually multi-tasking, but in reality we are not.

The one exception — The only exception that the research has uncovered is that if you are doing a physical task that you have done very very often and you are very good at, then you can do that physical task while you are doing a mental task. So if you are an adult and you have learned to walk then you can walk and talk at the same time.

Then again, maybe there isn’t an exception — Even this doesn’t work very well, though. In a study by Hyman et. al. in 2009, people talking on their cell phones while walking, ran into people more often and didn’t notice what was going on around them. The researchers had someone in a clown suit ride a unicycle. The people talking on a cell phone were much less likely to notice or remember the clown.

But young people can multi-task, right? – If you think that it’s only older people that can’t multi-task, think again. A study at Stanford University demonstrates that multi-tasking doesn’t work, even with college students. Clifford Nass’s study found that when people are asked to deal with multiple streams of information they can’t pay attention to them, can’t remember as well, and don’t switch as well as they thought they would – even college students.

So if multi-tasking is not effective what should you do? How do you effectively cope with all the input and distractions you have in your life, especially at work?

#1: Use the 80/20 rule — 20% of the work you do gives 80% of the impact and effectiveness. We often make the mistake of thinking that being busy means being effective. And the busier we get the more multi-tasking we end up doing. According to the research the result is that you are actually less effective. Focus on identifying the 20% of your tasks that are really effective, and do them one at a time.

#2: Implement “batch processing” — Do you sit at your desk with your email open and then get sucked into reading and answering emails all day long every time they come in? This encourages multi-tasking. Instead, try batch processing your emails. Decide on certain times of the day (in the morning, at noon, in the late afternoon, for example) that you are going to check and deal with email. Some people (Timothy Ferriss, for example, author of The 4-Hour Workweek) get really radical with this idea. Ferriss advocates that you check email once a day or less! If you are like me, that radical an idea is probably not feasible, but experiment with this idea of batch processing. You can use this not only for email, but for anything that is usually a distraction for you, such as making phone calls, checking voicemail, texting, etc. If you do batch processing you can then eliminate that task as a multi-tasking distractor during the other parts of your day.

#3: Work on your most important tasks first — I think one of the reasons that we give in to multi-tasking is that we feel more and more anxious as the day goes on that we have not accomplished what we wanted to, or what was important to us. So identify at the start of each day (or better yet, at the end of the day before) one or two really important things that you want to accomplish during that one day. Then do those tasks first. The sense of relief and accomplishment is immense, and you will find that you are more relaxed as the day goes on. You will not feel the anxious drive to do more and more and more, and it will be easier to resist multi-tasking.

#4: Use concentrated time — The opposite of multi-tasking is concentrated time. So if you are trying to stop multi-tasking you must start doing the opposite — give yourself blocks of time during which you are only working on one task. The idea of setting aside an entire day to work on that presentation you have coming up, may seem like it is impossible right now, but it doesn’t have to be an entire day. Start by taking one hour. Close down your email and all your other software. Turn off your phone or turn down the volume. Close the door to your office if you have a door. If you don’t have a door then figure out a place to go where people won’t find you. Then take that hour or 2 hours or half day or full day and work ONLY on the one task. You will be amazed at how much you will accomplish and how energized it makes you feel.

#5: Leave blank spaces – The research on creativity tells us that it is the pre-frontal cortex that puts ideas together. But the pre-frontal cortex can only work on one thing at a time. When you are multi-tasking you are taxing your pre-frontal cortex. You will never solve problems if your pre-frontal cortex doesn’t get quiet time to work on integrating information. This may sound paradoxical, but if you STOP thinking about a problem or particular topic you will then be able to solve it! This means you have to make time for blank spaces in your day. You need to have time in your day when you are doing “nothing” as far as your brain is concerned. Not talking, not reading, not writing. You can go for a walk, get exercise, listen to music, or stare into space. The more blank space the more work you will get done! Multi-tasking is the enemy of blank space.

#6: Accept it — The first step to change any behavior is to accept it! So if you want to stop multi-tasking the first thing you need to do is accept that you are multi-tasking and that multi-tasking is not effective. That might be the hardest step of all. We are actually addicted to the constant buzz of activity that multi-tasking gives us (see my blog post on dopamine). So just take a deep breath and accept that you’ve got this habit along with most of the people you know. Just noticing when you are doing it and saying, “oh, there I go again” will actually help tremendously in changing it. Putting your attention on what you want to change is a vital first step.

#7: Go “off grid” to re-calibrate – Last year I spent a week “off the grid” on an island in Lake Michigan. No internet, no email, no cell phones. I spent time on my computer (updating my iPhoto albums, etc), but not communicating with anyone online. It was different, interesting, and strange. I was actually glad to get back to the grid. But the experience made me think. The major difference for me was that I stopped “multi-tasking”.

When I was off the grid I found that I started doing one task at a time. I would do one thing for several minutes, and in many cases several hours. I believe that being online encourages task switching. When you can go from email to chat to texting to twitter to phone to facebook you switch tasks more. When I was off the grid all my communication channels were gone. So instead I spent time with one task and with one program. One day I worked in iPhoto for 3 hours straight. I think this week off grid “calibrated” my sense of what normal task switching is.

Less task switching = more happiness? — . I have found since then that I do less task switching. I’m not perfect. I fall into it sometimes, but since my week of re-calibration I follow the guidelines above more easily. I also believe that I am less agitated. It’s my hypothesis that task switching not only wastes time and increases errors. Task switching causes fatigue, exhaustion and agitation.