Chapter 5 argues that bad design causes accidents and mishaps, not human error. Seeking the root causes of failures and redesigning systems to address them is the only way to avoid repeating disasters. Norman promotes HCD as the path forward because it takes human behavior, including inattention, into account.

Understanding Why There is Error

Norman argues that machines require people to behave in unnatural ways, resulting in errors. Staying alert for hours while multitasking, for example, can result in mistakes that lead to financial loss, injury, and even death. Investigators typically seek the root cause of failures, assign blame, and punish the guilty with fines, more training, job loss, or jail time. As Norman observes, however, accidents result from a chain of events and can only be prevented by disrupting the chain.

Norman objects to solely blaming people for errors, urging investigators to look more closely for root causes. To this end, he advocates a technique called the “Five Whys,” which stresses the need to ask as many questions as necessary to determine the root cause of a problem. This technique prompts investigators to look beyond human error and discover the underlying issues behind failures. Humans are creative, exploratory beings who are prone to error.