Sense and decide
The Normal List
Recheck the problems the team has learned to live with
On a regular schedule, the team lists the problems it has decided are acceptable because nothing bad has happened yet, and asks whether each one still deserves that status.
Borrowed from sociologist Diane Vaughan's study of the 1986 Challenger launch decision, where she named "normalization of deviance," and from the board that investigated the loss of the shuttle Columbia in 2003. Read the original source.
Ongoing habit · An hour or more to set up · Needs senior backing · Start here for this problem
Try this first
Ask, "What do we see regularly that would have alarmed us the first time we saw it?"
Use it when
The team keeps a list of known issues that nobody looks at anymore, or explains away a recurring problem with "it's always like that."
Skip it when
The team is new to the work and has no history of accepted problems yet. It is also not for problems someone is already working on.
How to introduce it
Once a quarter, collect the problems the team has come to accept: recurring errors, workarounds, alerts people ignore, and numbers that are often a little off. For each one, ask three questions. When did we first see it? Why did we decide it was acceptable? What would have to happen for it to become serious? Anything where the answer to the last question is "not much" goes back on the active list.
How to show up
Treat every item as a fair question, not an accusation. The people who decided an issue was acceptable usually had good reasons at the time. Ask for items from the people closest to the work, since they see the oddities first. Leaders need to back the review, because some items will be ones leadership signed off on.
How long it takes
About an hour to build the first list. Thirty to forty-five minutes each quarter after that.
What makes it hard
Each accepted problem looks reasonable on its own, and the fact that nothing bad has happened feels like proof it is safe. People also worry that raising an old issue will look like second-guessing past decisions.
What it looks like when it's working
Items move back onto the active list, and some get fixed before they cause harm. If the list is the same every quarter and nothing ever moves, the review has become a ritual.
How long until it sticks
Expect two or three quarterly reviews before people bring items without being asked.
How you know it stuck
When people notice something odd, they say "that one goes on the normal list" instead of shrugging it off.
The idea behind it
Teams rarely miss warning signs because nobody saw them. More often the signs were seen, discussed, and filed as acceptable. Each time nothing bad happens, the team's sense of what counts as normal moves a little further.
Where it comes from
Research basis. Vaughan found that the engineers and managers behind the Challenger launch had seen damage to the booster seals on earlier flights and, one decision at a time, came to treat it as an acceptable risk. Seventeen years later, the board investigating the Columbia disaster found the same pattern with foam striking the shuttle. After earlier strikes, managers had downgraded the problem to a routine follow-up item and treated strikes as within normal experience. The evidence for normalization of deviance comes mainly from detailed studies of disasters, which are chosen after the fact. A 2023 review found 33 papers on the idea, and only 7 of them collected new data. The pattern is well described, but a regular review like this one has not been tested.