Four Responses to Overload

“A pattern is a way to generalize and transfer findings from one situation to others.”  

—Woods et al., Patterns in How People Think and Work: The Importance of Pattern Discovery for Understanding Complex Adaptive Systems

Overload is when the demands on a system, including its human operators, exceed their capacity to effectively manage those demands. It is so pervasive that people adapt to it without even noticing. What’s worse, our adaptations also conceal the fact that we are managing overload. All systems have various finite limits in capacity. The real world can and does routinely exceed those limits. As a result, adaptations to overload can be observed in almost all incidents. 

“The threat of being trapped in a workload bottleneck leads to four patterns of adaptation.”

—Woods et al.

There are four responses to overload, each with its own tradeoffs. Two responses are reactive and urgent: shed load or reduce thoroughness. The other two require anticipation and enough time to take effect: add resources, or time-shift workloads.

Four Responses to Overload

We shed load by dropping all but the most essential tasks—sometimes at a painful cost for the tasks dropped, or if we misread which is most essential. 

When we reduce thoroughness, spreading ourselves thin over every task, each task becomes more fragile—we trade off some immediate relief while increasing the likelihood that these points of fragility will break on us later.

The latter two responses depend on anticipation of the state of overload. When we add resources, bring in more people for example, it will take time to get them up to speed so they can usefully contribute to managing the workload. But recruiting people and onboarding them is itself additional work that must trade-off against our limited resources. Bringing in new automation also requires investment and training. Adding resources only works when there is enough time to absorb those delays. 

We can time-shift workloads: prepare some of the work ahead of time, or delay work to later. To do that effectively we need to understand changing tempos in our work. When we anticipate an upcoming rush, we need to act early enough to prepare those things that require extra time or care. Or we can choose to delay other work now if we know when things will slow down enough that we can return to it.

Here are a couple of examples of time-shifting in particular:

From Patterns in How People Think and Work: The Importance of Pattern Discovery for Understanding Complex Adaptive Systems: “Anesthesiology residents performed extra work during the set-up of the operating room before the patient entered, in order to avoid potential workload bottlenecks should certain contingencies arise later. When anesthesiologists needed some type of capacity to respond to acute physiological changes in a patient, they rarely had enough time or attentional resources available to carry out the tasks required to create the needed capability. Hence, expertise in anesthesiology, as in many high performance settings, consists of being able to anticipate potential bottlenecks and high tempo periods and to invest in certain tasks which prepare the practitioner to be highly responsive should the need to intervene arise.”

In the software context of scheduled database migrations, we typically prepare rollback plans. If something goes wrong during the migration, we are able to quickly recover. This is time-shifting some of the work of recovery ahead of the migration. There is another tradeoff here. If the database migration goes smoothly, and the prepared rollback proves unnecessary, we may feel in hindsight that those extra preparations were wasted.

Overload is pervasive. Knowing this model of four responses to overload can help us to recognize its presence, to choose better adaptations when we know there’s overload, and to anticipate ways overload can cascade from one part of the system to another. Through the study of patterns, insights from one specific challenge (such as overload) become pragmatic tools we can apply in otherwise unrelated situations. However, looking at a pattern in isolation from concrete examples can feel too abstract. We recommend you also read Expertise & Overload for a specific case which features real-world examples of all four responses to overload.

Eric Dobbs