Developing and using cognitive task typologies.

Based on experiences from case studies, some preliminary thoughts are presented regarding the why and how of developing a cognitive task typology model. Three different practical functions of such a typology are outlined: comparison, prediction, and design. These functions can be applied to sets of tasks both in the same and in different task worlds (e.g. artificial/laboratory tasks vs. real-life/case study tasks). Several existing techniques may be suitable for this purpose: hierarchical task analysis, verbal protocols, and the use of elementary cognitive modules. Finally two partly overlapping approaches to identify relevant task dimensions for a typology are outlined: one based on a macro-ergonomic view of human-machine systems, and the other centred around the cognitive concept of an operator's mental model of the task. In the Discussion a bottom-up strategy for typology development is advocated, and the relationship with task complexity is noted.