Context switching causes brain damage It is well documented that multitasking kills productivity. Can Scrum help you reduce waste created by context switching?

That multitasking causes waste has been documented well and is to my opinion a well known fact. The most referenced book is probably “In Quality Software Management: Systems Thinking” by Gerald Weinberg. Whenever this is referenced the following chart is presented:



Weinberg calculated that having just one project to focus on lets you spend 100% of your time on that. Adding just one project to two in total will cause you to lose 20% of your time to context switching. These numbers have proven to be true or even worse in real life scenarios. Another study done in 2007 with workers at Microsoft showed that even just responding to email or instant messaging lead to an average of 10 minutes or more resumption time. To truly get back to the task they were doing before the interruption it took an additional 10-15 minutes.

In addition to losing time to context switching it actually causes damage to your brain cells! Psychology Today reports the following:

A new body of research has found that multitasking makes people less efficient and reduces the level of brainpower used for each task. Also, people who overburden their minds with too many tasks at once can have problems with short-term memory.

Further it is reported that the mind slows down and adds a few seconds between each task. You get more stressed, causing a stress response. This stress response causes an adrenalin rush that can damage the cells that form new memories (short-term memory). In addition this stress response might weaken attentiveness and alertness.

It is pretty obvious what we should do – focus on on fewer tasks! In other words we should limit work in progress and avoid interrupts as much as possible. This is, as most of us know, easier said than done. For the most part it seems it is expected that you are available all day, on the phone, instant messaging, mail or in person. As an individual it isn’t easy to say no to management if they expect you to always be ready to shift your focus. Maybe Scrum can help us?

In Scrum the WIP limit is set per sprint, so that the team ideally only need to focus on the sprint backlog for any given sprint. Having a limited number of stories which are in play each sprint will help reduce context switching. However, it’s still possible that team members switch between backlog items. This could be because impediments limits team members from finishing the backlog item they are originally working on. If this is the case it is important to have a ScrumMaster that actively works to remove such impediments as soon as possible.

Pressure from external parties such as management or stakeholders could also cause team members to switch to and from backlog items. This interference with the team could also involve doing stuff that’s not even in the sprint backlog. In these cases it is important for the ScrumMaster to protect their team from such distractions. This protection could go as far as protecting team members for timeboxed bursts of work of 90-120 minutes followed by some recuperation time, so that during these bursts of work the team is not available for external interruptions.

The product owners also have an important job of demonstrating to management that focusing on fewer tasks and letting the team work uninterrupted is the best way to do things. Although the timeboxing of sprints in Scrum is one reason management might feel that Scrum is too rigid, there is a reason for this rigidness: Context switching is expensive. It is, as mentioned in an earlier blog post, possible to use an interrupt buffer each sprint. Here typical interrupts are calculated for. The thing about this buffer is that it should never overflow – if it does the sprint should be aborted. This is something management doesn’t want because aborts are visibly expensive – and thus interrupts will be kept at a minimum whenever they are kept visible through the use of an interrupt buffer.

All in all – Scrum can help reduce context switching. Sprint backlog reduces the number of items that can be worked on and ScrumMasters and Product Owners together protects the team from external interruptions. If you work on a team that is pretty much protected from external noise you also need to take action as an individual. Turn off your phone, exit Outlook (or whatever you are using) and exit whatever software for instant messaging you are using. Of course, I don’t think it’s realistic that you can always work like this, but having work bursts of 90-120 minutes where this strategy is used will without a doubt increase productivity.

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