Scrum Sprints and Vigilance Decrement
Scrum Sprints and Vigilance Decrement
A recent study from the University of Illinois sheds some light on one additional benefit of Agile sprints that reduces attention fatigue.
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I came across a study that challenges an old idea that attention is a scarce resource that decreases over time. As I read this article, I could not help but think about Scrum sprints. Many of us know a good deal about timeboxing and the benefits gained by minimizing overhead due to context switching, but it occurred to me that perhaps there are other forces that are contributing to the great gains when sprinting. We know that breaking large tasks into increments enables us to deliver value early and often, but perhaps these smaller incremental tasks, that are achievable in one sprint, also optimize the attention resources of the development team.
For 40 or 50 years cognitive experts believed there to be a consistent drop in "attentional resources" over time. They call this phenomenon "Vigilance Decrement" (Yates, 2011). I have seen managers who will attempt to manage this phenomenon by introducing incentives or demanding longer days. We have all observed similar behavior. However, a recent study by the University of Illinois overturns this decades-old theory and suggests a better way to maintain attention or productivity over time.
The study found that attention behaves similarly to sensory perception: “The brain gradually stops registering a sight, sound or feeling if that stimulus remains constant over time. For example, most people are not aware of the sensation of clothing touching their skin. The body becomes habituated to the feeling and the stimulus no longer registers in any meaningful way in the brain." (Yates, 2011). Also similar is a phenomenon of visual perception over time called "Troxler Fading": continual attention to a stationary object in one's peripheral vision can lead to that object's complete "disappearance" from view. (Yates, 2011).
The University of Illinois psychology team developed the following theory: given the way the brain fundamentally processes information, things that are true for sensations ought to be true for thoughts. “If sustained attention to a sensation makes that sensation vanish from our awareness, sustained attention to a thought should also lead to that thought's disappearance from our mind!" (Yates, 2011).
Using 84 study subjects divided into four groups, the University of Illinois team conducted an attention study and made the following conclusions: attention resources always exist in abundance and do not deplete over time. One starts performing poorly on a task not because they are depleted in attention but because their long-term task has become stale and begins to "disappear in their mind" — like the unchanging image in the peripheral vision.
Long tasks that span months incur an overhead because the brain becomes "habituated" to the task and begins to prioritize fresh stimulus — distractions. The mind is always paying attention to something and responds to change with fresh energy. The study suggests that prolonged attention to a large task actually hinders performance.
In addition to other benefits, it occurs to me that splitting backlog items into small effort stories keeps the collective brain energy of the team fresh by breaking long tasks into increments (stories) and introducing fresh work each sprint. This keeps these tasks from "disappearing" from the collective brain of the development team. It appears that the best way to manage attention over time and to optimize the attention resources of the development team is to break the work into small incremental tasks. This is common behavior on Scrum teams and perhaps another reason why we see big productivity gains using Agile Scrum.
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