Lecture 2a, G6DIHF
These lecture notes were not written as a course handout, but as a resource for lectures. Therefore, references and comments will not always be complete.
Recently you may have seen the Kegworth video. With the notes I gave you and some of the points I raised in the introduction, I hope this raised a number of issues for you and started you thinking about the issues of error, and of the contribution design has to make to the occurrence of such errors.
In this lecture, I will talk about a number of other accidents, large and small and consider not only what contributed to the accident, but also the problem of post-hoc analyses, types of error that occur and ways in which designs can be implemented to circumvent such errors occurring. A lot of the examples I give will illustrate how operator characteristics in terms of psycho-physiological baselines, fatigue, cognitive processing, and social situations all can contribute to disasters.
But first, I will summarise some of the things I talked about last week. Especially note that the products of Human Factors are not just evaluations of one particular incident but are also the development of models (predictive), principles (predictive), guidelines (prescriptive) and standards (prescriptive, legal). For example one of Norman's main guidelines is "design for error".
This lecture will investigate what 'error' means and how "errors" are of use to Human Factors experts. As Reason (1990) states
"human error is a very large subject, quite as extensive as that covered by the term human performance".
In this lecture all I can hope to do is give you a flavour for what human error is. Our purpose here is to motivate the study of the human operator in context, to determine what kinds of cognitive and social processing occurs and what kinds of issues people need to consider as designers of artifacts like computers. The point is to get you to adhere meaningfully to Norman's principle of "designing for error" by giving you a flavour for what features "cause" errors.
Reason states that there are two approaches to reducing this enormous area for investigation. The first is by taking a "broad but shallow stance aiming at a wide though superficial coverage of many well-documented error types or taking a narrow but deep slice, trading comprehensiveness for a chance to get at some of the more general principles of error production".
Last week I mentioned an approach in ergonomics called 'error ergonomics'. This approach involves collecting data on particular errors which occur and developing groups of regular errors that people make and then trying to design around them. This would be Reason's broad but shallow approach.
There has been renewed interest in the study of error since the Tenerife runway collision in 1977, Three Mile Island two years later, the Bhopal methyl isocyanate tragedy in 1984, the Challenger and Chernobyl disasters of 1986, the capsize of the Herald of Free Enterprise, the King's Cross tube station fire in 1987 and the Piper Alpha oil platform explosion of 1988.
In addition, theoretical and methodological advances since the mid 1970's in cognitive psychology have acted to make errors a proper study in their own right.
As Reason states "Not only must more effective methods of predicting and reducing dangerous errors emerge from a better understanding of mental processes, it has also become increasingly apparent that such theorising, if it is to provide an adequate picture of cognitive control processes, must explain not only correct performance, but also the more predictable varieties of human fallibility. Far from being rooted in irrational or maladaptive tendencies, these recurrent error forms have their origins in fundamentally useful psychological processes".
Ernst Mach (1905) put it well: "Knowledge and error flow from the same mental sources, only success can tell one from the other".
"Technology has run amuck. Rather than eliminating errors it merely changes the nature of those errors".
"Error will be taken as a generic term to encompass all those occasions in which a planned sequence of mental or physical activities fails to achieve its intended outcome, and when these failures cannot be attributed to the intervention of some chance agency". Reason, 1990.
Reason goes on the break this down into slips, lapses and mistakes. These will be considered below.