The term originates from computer science. However, it is just as applicable to mental tasks performed by humans. After all, the human mind is similar to a CPU in many ways.
Just as a CPU running multithreaded processes temporarily puts on hold an execution of a given thread while running another one, the human mind puts one task on hold in order to shift its focus to another one.
As Scott Hanselman once said: “The optimal number of threads in any system is one thread.”
Context switching happens when you’re doing a task and then stop doing it. You have to remember what task you were doing and how far along you were. Then when you come back to that task, you have to remember all that information and start off from where you were earlier.
Multitasking slows us down, reduces our speed and efficiency, drains our energy and causes more errors because we’re not able to pay enough attention.
A context switch is what slows down a computer when you give it multiple tasks. And it also slows humans down too.
Let’s get to the facts
- 41% of tasks are not resumed right away after an interruption.
- 23% of interrupted work not being resumed on the same day.
- It takes the average person around 15 minutes of uninterrupted work to reach total focus to perform a mentally challenging task.
- Most people average only 3 minutes on any given task before switching to something else (and only 2 minutes on a digital tool before moving on).
- Work is interrupted on average every 11 minutes and that it takes on average 25 minutes to become productive again after the interruption.
- The IQ of those who tried to juggle messages and work, fell by 10 points – the equivalent to missing a whole night’s sleep and more than double the 4-point fall seen after smoking marijuana.
Here comes the big guns!
According to computer scientist and psychologist Gerald Weinberg, taking on additional tasks simultaneously can destroy up to 80% of your productive time. Here’s how this looks in practice:
- Focusing on one task at a time = 100% of your productive time available
- Juggling two tasks at a time = 40% of your productive time for each and 20% lost to context switching
- Juggling three tasks at a time = 20% of your productive time for each and 40% lost to context switching
- With most workers these days trying to juggle 5 tasks at the same time, we’re losing up to 80% of our productive time each day just to context switching.
So what can be done about this?
It should be noted that the figures are open to interpretation. However, we can at least agree that any unintentional or intentional interruption of work yields waste. However, it is difficult to measure the suspension and resumption rates. One way to do this is in Kanban where the task in measured once entering and exiting the system. There can be no better way of highlighting waste when seeing increase in cycle and lead times.
Flow management methods, such as Kanban, look at the macro effects of context switching, as measured over the full lead time of tasks.
Robert Falkowitz
Types of Context Switching
| ABOUT | CONTEXT SWITCH |
|---|---|
| Starting a new task after having completed a different task. | (Old-Finished-New) |
| Choosing to work on a different task before having completed the current task, due to a blockage in the current task. | (Old-Blocked-New) |
| Choosing to work on a different task before having completed the current task due to a wandering mind. | (Old-Wandering-New). Mind wandering may be intentional or unintentional. |
| Being obliged by another party to stop working on one task and to start working on another. | (Old-Pre-empted-New) |
| Taking a pause while working on a task and returning to that task after the pause. | (Old-Paused-Old) |
| Interruptions during the course of the workday might be of the same context as the current task at-hand or they might be random, related to other topics. |
| There is evidently a difference between an expected interruption and an unexpected interruption. We not only perform better when we expect the interruption; we can only learn to improve performance following interruptions. |
| External interruptions are those that stem from events in the environment, such as a phone ringing, a colleague entering one’s cubicle, or an email signal. Internal interruptions are those in which one stops a task of her or his own volition. |
Suspension and resumption
| CONTEXT SWITCH | MEASURE |
|---|---|
| Old-Finished-New | This type of context switch is both inevitable and desirable. It represents the normal flow of work through a value stream. There is no suspension activity to be measured. |
| Old-Blocked-New | “Since I cannot advance on this task, I might as well start work on some other task” “Since I cannot advance on this task, let’s mobilize the necessary resources to unblock the task” From the moment when a worker recognizes that a task is blocked until the moment when the unblocking activity starts is theoretically measurable. |
| Old-Wandering-New | A bit of wandering could be especially beneficial when seeking new solutions to problems. On the other hand, as our mind wanders in unexpected directions, we are likely to arrive at dead ends. The are no feasible ways to measure wandering in the cost of context switching in a live environment. |
| Old-Pre-empted-New | Preventive maintenance is a common way of avoiding the urgent handling of incidents. Ask workers to report on the time spent on suspension activities. |
| Old-Paused-Old | If we pause work with the intention of returning to the same task after the pause, we have the chance to choose when to start the pause and to prepare the return to work. |
| Old-Finished-New | When the work on the old task is completed, the corresponding card is updated with the end time and moved to the completed column. There is no suspension activity to be measured. |
WANDERING FACTS
- Younger adults wandered more readily, but also regained focus more quickly.
- A low or depressed mood may lead to greater wandering.
- Inadequate sleep resulting in high levels of adenosine in the brain may provoke wandering.
- Dull, repetitive and mind-numbing tasks are more likely to lead to wandering than do challenging and novel tasks.
- More frequent external stimuli decreases the propensity to mind wandering. These external stimuli would correspond to the interactions between the collaborators.
- There are practices by individuals working alone that may also influence the frequency of mind wandering.