Swiss Cheese Model
What is the Swiss Cheese Model?
The Swiss Cheese Model illustrates how failures typically result from a combination of factors rather than a single root cause.3 These factors often include latent errors inherent in a procedure, machine, or system. The model is visualized as multiple layers of Swiss cheese, where the holes in each layer represent potential failure points. When these holes align, a failure occurs.
The Basic Idea
In recent years, a new area of study known as “safety science” has emerged. Safety science is fundamentally connected to several other fields, such as engineering and healthcare. Its scope is not limited to physical and psychological safety, but also includes issues of security, such as cybersecurity. Advancements in safety science aim to inform decision-making in a variety of disciplines.1 One model used by safety scientists to assess risk is the Swiss Cheese Model.
Every slice of Swiss cheese is full of holes. The size and number of holes will vary from one slice to another. In this model, a slice of Swiss cheese is symbolic of a given measure taken to minimize risk. Each slice of cheese can be thought of as a line of defense against accidents. Examples of different “slices” within a given organization may be management, allocation of resources, and an effective safety program.2
Each slice of Swiss cheese has its own unique set of holes. These holes represent shortcomings, or areas where there is potential for failure. Some slices may have more holes than others. When all of a given organization’s slices are stacked together, they represent the organization’s defense against risk as a whole. Since all the pieces of cheese have holes in different areas (which is representative of their differing weak points), sometimes one or more slices of cheese will cover a hole in another slice of cheese. This is symbolic of how some facets of an organization have strengths that can compensate for the shortcomings of others. However, sometimes holes will overlap, resulting in a hole that goes all the way through the stack of cheese. This represents a weak point that is common to all areas of a given organization, where there is the greatest potential for failure to occur.
Latent errors are triggered by active errors, which are unsafe behaviors carried out by individual parties. Thus, it is not simply mistakes made at the individual level that lead to an accident. In models of risk assessment, we must also consider the latent conditions that may be triggered by these errors.4
The Swiss Cheese Model has been used to help organizations understand why accidents occur in spite of their best efforts to prevent them. It is helpful for identifying weak points and for developing strategies to combat them. The goal of safety science is to maximize productivity while minimizing risk of harm, and the Swiss Cheese Model is an asset to the advancement of the field.
In order for a catastrophic event, such as a plane crash, to occur, a sequence of events precedes it. Think of these separate factors as slices of Swiss cheese lined up one behind the other. If any one of the holes in them doesn’t align with the others, the series of events is changed or curtailed, and a catastrophe is prevented. But if all the holes line up…the door is open for disaster.
– Sandra Brown in Low Pressure (2012)
About the Authors
Dan Pilat
Dan is a Co-Founder and Managing Director at The Decision Lab. He is a bestselling author of Intention - a book he wrote with Wiley on the mindful application of behavioral science in organizations. Dan has a background in organizational decision making, with a BComm in Decision & Information Systems from McGill University. He has worked on enterprise-level behavioral architecture at TD Securities and BMO Capital Markets, where he advised management on the implementation of systems processing billions of dollars per week. Driven by an appetite for the latest in technology, Dan created a course on business intelligence and lectured at McGill University, and has applied behavioral science to topics such as augmented and virtual reality.
Dr. Sekoul Krastev
Sekoul is a Co-Founder and Managing Director at The Decision Lab. He is a bestselling author of Intention - a book he wrote with Wiley on the mindful application of behavioral science in organizations. A decision scientist with a PhD in Decision Neuroscience from McGill University, Sekoul's work has been featured in peer-reviewed journals and has been presented at conferences around the world. Sekoul previously advised management on innovation and engagement strategy at The Boston Consulting Group as well as on online media strategy at Google. He has a deep interest in the applications of behavioral science to new technology and has published on these topics in places such as the Huffington Post and Strategy & Business.
