DIAGNOSTIC REASONING IN ACTION

The task of diagnosis is a very important topic in many different contexts. In highly complex technical installations involving high hazards, such as process plants, diagnosis is a crucial part of disturbance control; in technical maintenance, diagnosis is necessary to locate the root cause of system failures; and in medicine, diagnosis is the basis for any patient treatment. The paper presents a discussion of the basic nature of causal reasoning as applied for diagnosis and the mental strategies applied when diagnosis is viewed as an integrated part of ''natural decision making'' for interaction with the environment. A typology is suggested to characterize diagnosis in different domains such as process control, maintenance and medicine. In addition, an attempt is made to distinguish between the features of diagnosis depending on the ultimate aim, whether it is explanation, compensation, repair, or punishment and the difference in the context of the task, ''the causal field,'' related to the mental model involved in the different cases is outlined.