The Normalization of Deviance: How Acceptable Risk Creeps Upward

The Normalization of Deviance: How Acceptable Risk Creeps Upward On January 28, 1986, the Space Shuttle Challenger broke apart 73 seconds after launch, killing all seven crew members. The immediate cause was a failed O-ring seal in a solid rocket booster. But the deeper cause was far more troubling: NASA engineers had known about O-ring problems for years. They had seen evidence of erosion and blow-by on previous flights. Each time, when nothing catastrophic happened, the deviation from safety standards became a little more acceptable. Sociologist Diane Vaughan studied the Challenger disaster and coined the term "normalization of deviance" to describe this phenomenon. It is one of the most important mental models for anyone who makes decisions in complex environments -- which is to say, all of us. What Is Normalization of Deviance? Normalization of deviance occurs when people within an organization become so accustomed to a deviation from standard that they no longer consider it as dev