Human error skill-based

Human Error Skill-based errors Slips of action... 

The classification of human error within the FASGEP project takes into account the woric of Rasmussen, specifically the classification of Rule-Based errors, Skill-Based errors, and Knowledge-Based errors. The causal relationships for each of the classifications have been developed into a causal network. A type of graphical probability model is based on this. 

A relatively simple model has been developed by Rasmussen to quantify human error rates based on the level of training (Rasmussen (1979, 1981)). This model divides the behaviour into three basic categories skill-based, rule-based, and knowledge-based behaviours. 

The classification structure for PIFs used in this chapter is based on the model of human error as arising from a mismatch between demands and resources which was described in Chapter 1, Section 1.6 (Figure 1.6). In this model demands were seen as requirements for human performance which arise from the characteristics of the process environment (e.g., the need to monitor a panel or to be able to fix a seal in a flange) and the nature of the human capabilities to satisfy these demands (e.g., skills of perception, thinking, and physical action). These demands are met by the individual and group resources of personnel and the extent to which the design of the task allows these resources to be effectively deployed. Where demands exceeded resources, errors could be expected to occur. 

Advocates of the global approach would argue that human activities are essentially goal-directed (the cognitive view expressed in Chapter 2), and that this cannot be captured by a simple decomposition of a task into its elements. They also state that if an intention is correct (on the basis of an appropriate diagnosis of a situation), then errors of omission in skill-based actions are imlikely, because feedback will constantly provide a comparison between the expected and actual results of the task. From this perspective, the focus would be on the reliability of the cognitive rather than the action elements of the task. 

Skill-based (S-B) errors are not easily prevented because of the highly automatic (or unconscious) open-loop character of this level of behaviour either you learn to live with them, or you change the task environment in which they occur, when human error seems to have been built in (quite predictably) in the design stage. Especially ergonomics may contribute in... 

As was discussed in Chapter 2 Rasmussen has provided the basic model of human error based on three levels of behaviour skill-, rule- and knowledge-based (S-B, R-B, K-B). This SRK model has been operationalised to describe operator errors in process control tasks by combining it with characteristic task elements, which as a whole cover the entire spectrum of operator subtasks. 

Skills, rules, and knowledge model Models human information processing in terms of three levels of behavioral control skill based, rule based, and knowledge based Models the processes and requirements for each level of behavior Can be used with quantitative models of human performance to estimate task time and errors... 

The attractiveness of systems and engineering approaches in reducing safety incidents has unfortunately not eUminated individual behaviour as the most frequently reported cause. An analysis by Endsley (1999), that most human error incidents resulted from a loss of situational awareness (SA) rather than judgement or skill based decisions, emphasized the importance of attention recovery mechanisms for safety critical roles. Marty papers have been published dealing with attention recovery and fatigue countermeasures to date, however, none have been found that include a mechanism to enable instantaneous and cued recovery at the moment of demand. This chapter formalizes a practice based approach to recovery of SA delivered in over 20 years of counselling and coaching performance with a diversity of clients. 

Other authors like Jens Rasmussen ([14], [15]) distinguish between different levels of human performance and correlate them to required attention and familiarity with the task, cf. Fig.5. It is evident that knowledge-based actions are associated with the highest error probability, but most actions required from a car driver are rule based like obeying traffic signs, or skill-based like changing the gears. 

The tasks of hazard identification and risk assessment are closely linked— both require the assessors to visualize the operation (Cooper and Chapman 1985). In a complex situation, particularly one that does not yet exist in reality, it may be difficult to visualize all the factors that affect the risk, which leads to a greater likelihood of human error. Therefore, staff must be trained in how to perform a risk assessment. The skills needed wiU often be fuUy developed only after some considerable period of working in the real environment. Training is obvionsly extremely important, bnt the conventional classroom-based training is often ineffective (Bransford et al. 1986) and training in the real environment will inevitably expose inexperienced personnel to the very risks that companies are aiming to minimize. 

Slips (execution errors) and lapses (memory errors) occur at the skill-based performance levels. They are due to the intrinsic variability of human actions with respect to place, force and time co-ordination. 

---