In this article, Rasmussen presents the concept of human error, and how complex and dynamic environments should shift the focus of error. The author argues for a general understanding of human behavior and social interactions in cognitive terms. He presents three cases to analyze human–system interactions, including traditional task analysis and human reliability, causal analysis after an event, and design of reliable work conditions in modern sociotechnical systems. Rasmussen highlights the need for errors to be studied in the context of cognitive control of behavior in complex environments.