Normalisation of deviance is the process where what was unacceptable gradually becomes acceptable over time in the absence of failures. So, the longer a period without incidents, a requirement to wear a hard hat may start to be taken less seriously and later ignored. The unacceptable becomes the norm, no longer seen as deviant.

The term was used by Diane Vaughan when discussing the culture and events leading to the Challenger disaster. However, it’s easy to recognise it in much more mundane examples.

Classic workplace examples where deviance may start to become normalised include:

Normalisation of deviance can be particularly tricky to avoid when failures are rare yet severe or with known but distant dangers, such as smoking.

The Normalisation of Deviance

A phone zombie is a regular pedestrian turned zombie walker because they’re busy staring at their phone.

Sometimes it’s hard not to be a phone zombie—whether it’s a notification about where you’re about to meet, a message about something you just finished at work, texting to say you’re on your way home, a sudden thought to look something up, reading a weekly newsletter, or maybe it’s just switching the podcast. On a long, quiet street on my commute, I’ve also read a book while walking. There are so many reasons why it’s easy to turn into a phone zombie walking unthinkingly down the street.

Once, while waiting for a crossing light to change and checking train times on my phone, I noticed the people around me starting to cross. Taking my cue, I began to walk too, only realising a few steps later, with a car bearing down on me, that the light hadn’t changed to signal it was ok to cross. I’ve also seen people walk into cyclists, a near miss with a bus driving close to the curb, and someone tripping and falling. Take care, and don’t let it be you!

Also known as smartphone zombies, smombie for short, or zombie pedestrians.

You can get a printed gift of phone zombies, but as zombies aren't that nice to look at, I also made a friendlier version of phone zombies

Also see: continuous partial attention, when drinking tea and phubbing

Phone zombie

I always considered a checklist, a checklist, so I was interested to learn the distinction between two types of checklists: Read-Do and Do-Confirm.

A Read-Do checklist might be prepared in advance for several potential possibilities. You check off the tasks as you do them, like following a new cooking recipe. They may be geared towards helping people understand what they should be doing and in what order and helping them remember key steps in unusual or unplanned scenarios. So, for example, if a plane develops a particular type of rare fault, such as an engine failure, a Read-Do checklist could be pulled out for that scenario. The pilot and crew can use it to make the most of others' past experiences and failures. Even with training, given the situation's relative rarity, and especially if a serious situation might interfere with normal thinking, a Read-Do checklist helps steer the crew to safe outcomes without relying solely on training and memory. The calm security and simplicity of steps of a checklist can be just what's needed.

A Do-Confirm checklist is more of an aid to memory to make sure nothing gets missed. It's a safety net for normal operation catching lapses in memory. In principle, we know what to do, so we run through those steps from experience and memory and use the Do-Confirm checklist at a designated pause point to ensure we didn't miss anything. The WHO Safe Surgery checklist has helped save 1,000s of lives.

Because a simple checklist can never account for every unexpected occurrence in complex environments—for example, healthcare, aviation, building a skyscraper, or software projects—both checklist types can benefit from items that require a communication step. An item can just be to ensure that all those with the relevant knowledge have discussed things. It's a simple and powerful way to improve outcomes across a wide range of unexpected scenarios.

I learned about the simple power of checklists, the two types, and the resistance to adopting them—from Atul Gawande's, The Checklist Manifesto: How to get Things Right.

Two types of checklists: Read-Do, Do-Confirm

The tomato test, or tomato slicing test, is a handy way to see if your knives could do with sharpening. The idea is that a properly sharpened blade should slice through the taut skin of a tomato with minimal pressure.

Somewhat counterintuitively, most cooks seem to agree that sharp knives reduce the risk of accidents as you don't have to push down as hard as with blunt knives.

To do the tomato slicing test: Place a tomato on a board and gently run the knife over the top surface. A sharp blade will glide through the tomato skin, cutting it precisely all the way down. You shouldn't need to apply any pressure if the knife has weight. If you need to push down to pierce the skin, it could be time to sharpen.

Cutting the top off the tomato first allows it to sit stably on its end, so you don't have to hold it.

Alternatively, you could use a serrated knife which is handy for foods with a hard outside and a soft inside.

The sharper the knife, the less mess you'll make and the easier you can ghost cook.

The tomato test

We all know that racing drivers overtake on the inside — it's the shorter, faster route. It was only relatively recently that I found how useful it can be on a long drive, too, not for racing but for using the bend on a multilane road for easier, safer overtaking.

Perhaps this scenario will resonate: after cruising at a steady speed for miles of a long journey you slowly catch up with a car traveling just a few miles an hour slower. You're not driving fast enough to zip by them, but the difference is enough to slow your steady progress on a long journey, and if you're driving near the speed limit anyway you probably don't want to accelerate much to overtake.

On a multi-lane road like a motorway or freeway — not a single lane road where you'd be overtaking with reduced visibility on the corner in the opposing lane — timing your overtaking so you're on the inside of a bend and the slower car is on the outside allows you to get round the slower driver in a shorter time and without needing to travel nearly as fast.

And the converse is also true: if you've timed your overtaking when approaching a bend where you'll be on the outside you'll find that you'll have to go a lot faster to get round or perhaps that your intended overtaking is actually not getting you past at all.

Passing on an inside bend

The Swiss Cheese Model helps explain why, despite all our best intentions, accidents happen.

Analysis of accidents in large complex systems such as power stations or plane crashes led to an understanding that "no one failure, human or technical, is sufficient to cause an accident. Rather, it involves the unlikely and often unforeseeable conjunction of several contributing factors arising from different levels of the system."

James Reason's Swiss Cheese Model is a memorable visual metaphor that illustrates how each safeguard may contain a latent flaw or hole and that an unfortunate circumstance may result in these holes lining up to disastrous effect. It's also a nice reminder that multiple layers of defence will be more effective, but even with our best efforts, there's still potential for something to go wrong.

Excerpt from Revisiting the "Swiss Cheese" Model of Accidents (pdf), Reason, Hollnagel and Paries, 2006.

Coronavirus example from the Cleveland Clinic.

I learned recently that it's sometimes called the "cumulative act effect".

This sketch, updated and polished, features with a number of others in my book Big Ideas Little Pictures.

The Swiss Cheese Model

Forcing functions are a super way to help make things foolproof, or better, errorproof — as all of us make mistakes with designed things without being fools. You may have used your own forcing function when, in an attempt to make sure you remember your passport or tickets before a flight, you put them directly in front of the door so you couldn’t open it without noticing them. That little dialogue that asks you if you want to save your changes before closing your work, that’s a forcing function too.

My first memory of understanding a forcing function was when working with a giant machine capable of cutting through 100 pieces of paper at a time. The two buttons to operate it were on opposite sides of the machine. I couldn’t start the machine without spreading my arms out wide. There was then no way to also accidentally have your fingers in with the paper and near the blades when it started. Smart.

I learned this sense of forcing function from Don Norman’s classic The Design of Everyday Things. Also from Don, see Mapping.

The other sense of forcing functions for productivity is also really useful: helping kick ourselves into action.

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Category: safety