Errors: An Inherent Part of Human-System Performance - Foundations for Designing User-Centered Systems - page 279

Erroneous actions, then, can be seen generally as the result of one of two things:
1. Performing the right action in the wrong circumstances. This is what Reason
( 1990 ) calls a mistake, or a failure in planning.
2. Performing the wrong action in the right circumstances. This is often referred to
as a slip (Norman 1981 ; Reason 1990 ), or failure in action execution.
In either case the action could have been deemed correct if the circumstances
had been slightly different. This helps to explain Rasmussen's ( 1988 ) description
of erroneous actions as being the results of carrying unsuccessful experiments in
unfriendly environments.
It is also important to take into account different perceptions when trying to
interpret what people mean by error. Rasmussen et al. ( 1994 ) suggest that the
following perspectives can be identified:
• Common sense: to explain an unusual event
• The lawyer: to find somebody to blame and/or punish
• The therapist: to improve human performance
• The scientist: to understand human behavior
• The reliability analyst: to evaluate human performance
• The designer: to improve system configuration.
As interactive system designers, our perspective tends to be mostly a combi-
nation of the scientist's and the designer's perspectives. The two are somewhat
related, because by understanding the human behavior, we can provide appropriate
support to prevent errors happening or to mitigate the consequences of any errors
that may not be preventable. In most cases this will be by changing the design of
the system.
10.1.2 The Fine Line Between Success and Failure
As long as there have been people, there have been errors. Getting things right is
not always easy, and often requires knowledge and skills that have to be acquired
over an extended period of time: you cannot become an expert overnight. One of
the ways in which people learn is through practice, by reflecting on their perfor-
mance, using feedback, and then trying to do it better next time. This approach is
nicely illustrated in the works of Henry Petroski (e.g., Petroski 1985 / 1992 , 1994 ,
2006 ), who has shown how the development of engineering has progressed over
the centuries by learning from past errors.
The study of errors has fascinated psychologists for over a century. It received
renewed impetus from the end of the 1970s with major events like the Three Mile
Island disaster in 1979, the runway collision at Tenerife in 1977, and a range of
catastrophes in medical care (e.g., Bogner 2004 ), when the gauntlet was picked up
by the human factors and ergonomics community. The focus of study has changed
somewhat, however, and there is now recognition that it is important to think about