Story of my life: I read a book, come across an interesting concept, Google it – and fall into a rabbit-hole of information I have never heard of before. It’s 11 PM and here I am writing about mathematical concepts and psychological principles. The conclusion is – spoiler alert – to reduce the amount of work in progress, because this is beneficial in getting things done.
A mathematical approach
It all began when I came across Little’s law. Little’s law is a key concept in queueing theory, and applies to ‘queuing systems’. These are systems in which work comes in and goes out. Compare it to a queue at a bank. Standing in line is never an end in itself. You queue up, spend time going through the process, and when it’s your turn, you finally do what you’ve been queuing for (so in this case, being helped by the clerk). Another example of a queuing system to consider is a production line. Little’s Law establishes a linear relationship for queuing systems between the Lead-Time (LT), the Work-In-Progress (WIP) and Throughput (TP), expressed as: LT = WIP / TP.
Articles I have read online mainly refer to using Little’s Law in Kanban. One result of Little’s Law is that if multiple tasks are worked on simultaneously within the workflow, the longer (on average) it takes to complete each of these tasks. A wise lesson to be learned from this is not to let too many things (read: Product Backlog Items) be ‘work in progress’ during a Sprint at the same time.
A psychological approach
However, there is another factor that influences the ‘work in progress’. Let’s take a look at the cost of task switching.
In cognitive psychology it is argued that our brains can store a limit of an average of seven objects (plus/minus two) in short-term memory (this is referred to as Miller’s law). Therefore, when switching tasks, information has to be unloaded and other information has to be loaded and processed. Susan Weinschenk, Ph.D. argues that multi-tasking can cost you 40 percent of your productivity!
Reduce waste, reduce work in progress
Switching tasks is listed by Matt Stine as one of the seven wastes of software development. Stine lists four rules to battle task switching:
- Minimizing the amount of context switches: reduce the amount of simultaneous projects;
- Rotating the responsibility for handling interruptions throughout the team;
- Eliminating unimportant work and interruptions: if it is not delivering value, it should not be done;
- Ensuring that all of the knowledge necessary to complete assigned work is in the right hands.
It’s important for the Scrum Team to be mindful of these four rules. There is a vital role for the Scrum Master to be instrumental in preventing too much task switching – which can be a pretty big impediment!