CREAM - Cognitive Reliability and Error Analysis Method  

Human work can be characterised by a scale going from "doing" to "thinking". Some tasks, such as manual skills and following a procedure, require much "doing" and little "thinking", while others, such as diagnosis, planning, and problem solving, require much "thinking" and little "doing". The development of modern technology has changed the nature of human work from being mostly manual skills to being mostly knowledge intensive functions (i.e., cognitive tasks). In present-day industrial environments the amount of "thinking" is increased while the amount of " doing" is reduced. This state of affairs has consequences for both system design and reliability analysis. In system design, for instance, conventional ergonomic aspects must be replaced by cognitive ergonomics. Similarly, in risk assessment and reliability analysis, first generation Human Reliability Analysis (HRA) must be replaced by a second generation, context-dependent cognitive reliability analysis.

CREAM (Cognitive Reliability and Error Analysis Method) is a specific proposal for a second generation HRA. CREAM will enable an analyst to achieve the following:

1. Identify those parts of the work, as tasks or actions, that require or depend on human cognition, and which therefore may be affected by variations in cognitive reliability,

2. Determine the conditions under which the reliability of cognition may be reduced, and where therefore these tasks or actions may constitute a source of risk,

3. Provide an appraisal of the consequences of human performance on system safety which can be used in a PRA/PSA, and

4. Develop and specify modifications that improve these conditions, hence serve to increase the reliability of cognition and reduce the risk.

Steps 1 - 3 are the core of CREAM. Step 4 serves the purpose of ensuring that the proper conclusions are drawn from the analysis, and that the necessary changes to the system are correctly specified.

CREAM can be used in several different ways:

• as a stand-alone analysis method, for either retrospective or prospective analyses, using a consistent taxonomy for error modes and error causes.

• as part of a larger design method for complex, interactive systems,

• as an HRA in the context of an Integrated Safety Analysis (ISA) or Probabilistic Safety Analysis (PSA).

CREAM provides the core functionality of these services, i.e., the concepts, the classification system, the cognitive models, and the methods. In order to be properly used it is necessary to supplement with application or plant specific information, e.g. in the form of values for specific performance parameters, detailed operational and process knowledge that defines the context, etc. CREAM has been developed as a written guideline supported by a hypertext tool. A full description can be found in the book "Cognitive Reliability and Error Analysis Method", published by Elsevier (1998).

A specialised version of CREAM for use in the analysis of traffic accidents has been developed as part of the FICA project. The adapted version was named DREAM, for Driver Reliability and Error Analysis Method. Later, a version was developed for use in maritime accident analysis. It was appropriately named BREAM - B for the ship's Bridge.

See also the items on Accident Modelling and "Human Error".

© Erik Hollnagel, 2006

Back