The Swiss Cheese Model

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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.

Also see:

Published 3 Oct 2020

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When teaching framing at UC Berkeley, Professor George Lakoff would often begin with a simple test: "Don't think of an elephant." Except everyone does. When he said elephant, like it or not, all things elephant—large, slow, floppy ears, tusks, trunk, jungle, savannah—were likely to come to mind. Lakoff gives another example: When Richard Nixon came on TV and said, "I am not a crook," everyone thought about him as a crook, even though he explicitly said he wasn't. Another case he shares is when someone says tax relief, it evokes a frame whereby taxes are a burden, someone imposing those taxes is hurting people, someone relieving you of that hurt is helping you, and anyone who wants to stop that relief is a villain. Suppose you think taxes are good, not bad; if you use the term tax relief when arguing against it, you're setting yourself up as the villain. Using someone else's language draws you into their worldview. Some Framing Examples Here are some more everyday examples of framing at work: Taking sides in an argument suggests there has to be a winner and loser. When someone helps you, saying "I owe you one" frames the favour as a transaction to be repaid rather than a gift. Stay-at-home parent and working parent evokes a frame where staying at home isn't work. Quality time frames certain family moments as more valuable and implies that some time is less meaningful. Screen time evokes a frame of off-screen vs on-screen time, as opposed to considering the value of what you're doing, whether on-screen or off. Reframing Signage I love spotting signs that shift the frame in positive, thoughtful ways. Rather than presupposing bad behaviour, they invite good. For example, this sign from Kew Gardens: "Respecting Significant Trees Please help us manage our trees to ensure we can enjoy them for as long as possible. This tree needs a break from adults and children climbing on it. Please don't climb." Rather than setting Kew up as the rule-enforcer spoiling your fun, it frames them as caretakers—inviting you to help give a tired tree a break. Not climbing becomes an act of kindness, not a restriction. Not climbing becomes an act of respect rather than restriction. Our local wetlands has a "Ducks only" sign instead of an admonishing "Keep off the grass". Or at an ATM, even saying "Wait" rather than "Don't remove your card" helps keep removing your card further from your mind. A reader shared with me that as a lifeguard, he learned to yell "Walk!" rather than "Don't run!" A positive action to take is direct, rather than a negative that needs to be processed—see Point Positive. Language shapes and reflects how we think. Using language that negates a frame evokes the frame. What frames are you evoking? Related Ideas to Don't Think of an Elephant Everything I've learned about framing, metaphor, and how they shape our thinking continues to fascinate me. Here are some related sketches and powerful metaphors: Primary metaphor The Frog Boil Metaphor Rivers and Buckets Compliments are Gifts The Learning Pit The Swiss Cheese Model Trust Battery The Accountability Ladder Sharpen the Saw Ideas Are Locations, Objects, Food Framing Get More Participation: Instead of "Anything Else?" ask "What Else?"…When teaching framing at UC Berkeley, Professor George Lakoff would often begin with a simple test: "Don't think of an elephant." Except everyone does. When he said elephant, like it or not, all things elephant—large, slow, floppy ears, tusks, trunk, jungle, savannah—were likely to come to mind. Lakoff gives another example: When Richard Nixon came on TV and said, "I am not a crook," everyone thought about him as a crook, even though he explicitly said he wasn't. Another case he shares is when someone says tax relief, it evokes a frame whereby taxes are a burden, someone imposing those taxes is hurting people, someone relieving you of that hurt is helping you, and anyone who wants to stop that relief is a villain. Suppose you think taxes are good, not bad; if you use the term tax relief when arguing against it, you're setting yourself up as the villain. Using someone else's language draws you into their worldview. Some Framing Examples Here are some more everyday examples of framing at work: Taking sides in an argument suggests there has to be a winner and loser. When someone helps you, saying "I owe you one" frames the favour as a transaction to be repaid rather than a gift. Stay-at-home parent and working parent evokes a frame where staying at home isn't work. Quality time frames certain family moments as more valuable and implies that some time is less meaningful. Screen time evokes a frame of off-screen vs on-screen time, as opposed to considering the value of what you're doing, whether on-screen or off. Reframing Signage I love spotting signs that shift the frame in positive, thoughtful ways. Rather than presupposing bad behaviour, they invite good. For example, this sign from Kew Gardens: "Respecting Significant Trees Please help us manage our trees to ensure we can enjoy them for as long as possible. This tree needs a break from adults and children climbing on it. Please don't climb." Rather than setting Kew up as the rule-enforcer spoiling your fun, it frames them as caretakers—inviting you to help give a tired tree a break. Not climbing becomes an act of kindness, not a restriction. Not climbing becomes an act of respect rather than restriction. Our local wetlands has a "Ducks only" sign instead of an admonishing "Keep off the grass". Or at an ATM, even saying "Wait" rather than "Don't remove your card" helps keep removing your card further from your mind. A reader shared with me that as a lifeguard, he learned to yell "Walk!" rather than "Don't run!" A positive action to take is direct, rather than a negative that needs to be processed—see Point Positive. Language shapes and reflects how we think. Using language that negates a frame evokes the frame. What frames are you evoking? Related Ideas to Don't Think of an Elephant Everything I've learned about framing, metaphor, and how they shape our thinking continues to fascinate me. Here are some related sketches and powerful metaphors: Primary metaphor The Frog Boil Metaphor Rivers and Buckets Compliments are Gifts The Learning Pit The Swiss Cheese Model Trust Battery The Accountability Ladder Sharpen the Saw Ideas Are Locations, Objects, Food Framing Get More Participation: Instead of "Anything Else?" ask "What Else?"

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