Erik Hollnagel

Birds do it: The ETTO Principle

Surprisingly, it is the investigation of "non-accidents" that most inspires Erik Hollnagel in his work as a professor and widely published author on safety in various domains, including nuclear power generation, aerospace and aviation, air traffic management, software engineering, health care, and land-based traffic. In his talk to a packed Namahn library, Hollnagel explained that accident investigation and risk assessment models universally focus on what goes wrong and the elimination of "error". While this principle may work with machines (an approach dating back to the Industrial Revolution), it does not work with humans, who are a common element in all accidents. Variability in human performance is inevitable, even in the same tasks we repeat every day.

Hollnagel explained how our need to identify a cause for any accident has colored all risk assessment thinking. However, we don't "find" causes; we "create" them, and when none can be found, we use the "act of God" opt-out clause. This is a social process, which changes over time just as thinking and society change: after the Second World War and until the late 1970s, most accidents were seen as a result of technical failure. The Three Mile Island accident saw the cause shift from technical to human failure. Finally in the 1980s with the Challenger disaster, the cause identified was not solely technical or human but organizational. The current financial crisis is another such organizational accident and future accidents will no doubt inspire us to find new causes by which to describe them.

Hollnagel would prefer to be able to explain why for most of the time we do things right and to use this knowledge to shift accident prevention thinking from cause identification to understanding and supporting human creativity, learning and performance variability.

Resilience Engineering (also the subject of Hollnagel's latest book) proposes a simple principle, which when applied to any situation or domain, can reveal the "trade-offs" we make in the pursuit of attaining our goals: the Efficiency Thoroughness Trade-off (ETTO) principle. We make these trade-offs for a variety of reasons in order to get something done: on the side of thoroughness, we pay more attention to safety; on the side of efficiency, we do things faster. These trade-offs are not made for any bad reason, but for the greater good. In an example taken from nature, Hollnagel argued that birds display ETTO every day when they risk eating in the open, where food is plentiful and the danger is greatest, as opposed to eating less but in safety. Indeed, human ability to adjust performance to changing circumstances is also a key to our success and for most of the time, things go right, but occasionally and inevitably, an unforeseen combination of the same trade-offs result in accidents. The origin of both success and failure is the same: performance.

Today the systems we depend upon are complex, intractable, interdependent and constantly changing. Our safety is the ability to succeed in varying circumstances. Therefore, we need to build human performance variability into these systems. Hollnagel argued that if our performance varies on the side of failure (the current focus of risk assessment), it equally varies on the side of success, which is where we should also be focusing our attention. He believes this would be a leap forward in the thinking around accident prevention and would make a positive contribution to the design of socio-technical systems and management.

Erik Hollnagel

Erik Hollnagel (PhD, psychology) is Professor and Industrial Safety Chair at École des Mines de Paris (France), Professor Emeritus at University of Linköping (Sweden), and Visiting Professor at the Norwegian University of Science and Technology (NTNU) in Trondheim (Norway). He has since 1971 worked at universities, research centres, and industries in several countries and with problems from several domains, including nuclear power generation, aerospace and aviation, air traffic management, software engineering, healthcare, and land-based traffic.

His professional interests include industrial safety, resilience engineering, accident investigation, cognitive systems engineering and cognitive ergonomics.

He has published more than 250 papers and authored or edited 13 books, some of the most recent titles being "Resilience Engineering Perspectives: Remaining Sensitive to the Possibility of Failure" (Ashgate, 2008), "Resilience Engineering: Concepts and Precepts" (Ashgate, 2006), "Joint Cognitive Systems: Foundations of Cognitive Systems Engineering" (Taylor & Francis, 2005) and "Barriers and Accident Prevention" (Ashgate, 2004). Erik Hollnagel is, together with Pietro C. Cacciabue, Editor-in-Chief of the international journal of Cognition, Technology & Work.