“There is time enough for everything in the course of the day, if you do but one thing at once, but there is not time enough in the year, if you will do two things at one time.”  — Philip Stanhope, 4th Earl of Chesterfield

When our children were young, we ate a lot of burnt food. We said that it had been “cooked with love”. I used to explain that only someone who loves you would serve burnt food. People who don’t love you would never dream of serving burnt food. But the real reason for the burnt food is that children need a lot of attention, and those needs for attention don’t go away, just because it’s time to get dinner on the table. And when it came to choosing between helping our children with a problem or paying attention to what was bubbling on the stove or baking in the oven, our children were often our top priority.

It was a classic problem of human factors.

The Myth of Multitasking

In 2008, Christine Rosen published an essay in The New Atlantis and Dave Crenshaw published a book, both called “The Myth of Multitasking”. In fact, Rosen used the quote from Lord Chesterfield in her essay. The point that both make is that we are not able to do two things at once—at least not two things that both require attention. Things like helping a child with their homework AND cooking dinner, or like monitoring the board in the control room AND filling out the shift log. Instead, we switch between the multiple tasks, giving none of them our full attention. So, instead of multitasking, doing several things at once, we are switch tasking.

But switching between tasks takes time and comes at a loss of focus. Worse, we sometimes, don’t switch back to the original task as quickly as it requires.

The Cost of Switch Tasking

Kunal Gupta has written a lot about multitasking and switch tasking. He offers driving as an example of multitasking: “driving a car involves checking the rearview mirror, watching the odometer, looking at the side mirrors, checking blind spots, oh and looking ahead of you through the windshield.” But even these are not done simultaneously. They are done sequentially, switching from one task to another. If you spend too much time on the support tasks—checking mirrors, checking instrumentation, checking the interior or surroundings of your vehicle—the primary task of looking ahead of you through the windshield is neglected and can result in catastrophe.

Driving works because we practice switching between these tasks quickly. Checking a mirror works because it only takes a glance. It only takes a glance because we know exactly what we are looking for. If the glance in the mirror reveals anything unexpected, then it gets a second glance, or a long stare, and we are distracted from our primary task.

Switching between tasks takes time. We must disengage our focus from one task and direct it to the new task. That time is time not spent on either task, so it costs efficiency and productivity. The more disparate the tasks, the longer that switching takes.

When the tasks involve safety, focus is essential. Switch tasking comes at a cost of lost focus.

Unintentional Switch Tasking

The idea that multitasking, or more accurately, switch tasking, is counter-productive is widely accepted. People are less likely to brag about their multitasking abilities now, knowing that the response will be something along the lines of Dave Crenshaw’s comment:

“When someone says they’re ‘good at multitasking,’ they’re really saying they’re inefficient. It’s like publicly admitting you’re going to make it a habit to screw up multiple things at the same time. And, ironically, people who consider themselves great at multitasking are statistically more likely to be the worst at it.”

So, we’re learning to not switch task on purpose. But what if switch tasking is imposed on us.  Or just as bad, what if we’re imposing switch tasking on others. That’s when safety can suffer the most.

Human Factors Must Take “Multitasking” into Account

When we talked about “cooking with love” it was about a task with low stakes. If the pot boiled over, cleaning the stove was a little harder, but not impossible. If the food burnt, it didn’t taste as good, but usually it was edible, and if not, we ordered out for pizza.

In a process, if a pot boils over or overflows, the stakes are much higher. Economic loss at the least, environmental damage, injuries or fatalities in the plant, and worst of all, the potential for injuries or fatalities in the community.

We have an important job to do running our processes, one that requires our focus. It gets increasingly more complex, and somehow, we are expected to keep up with that increasing complexity by ‘multitasking’. It doesn’t work, and we need to be on guard against it. Our consideration of human factors needs to consider whether we are trying to do too much all at once.


  • Mike Schmidt

    With a career in the CPI that began in 1977 with Union Carbide, Mike was profoundly impacted by the 1984 tragedy in Bhopal and has been working on process safety ever since.