Diagrammatic information

Diagrams are increasingly used to present complex and abstract information. Their ultimate success as tools for communication depends largely upon how effectively they can be processed in the mind of the viewer. The application of established principles of graphic design is a vital part of developing effective diagrams, but tends to focus upon external aspects of representation that apply at a general level across a wide range of subject domains. However, the internal (mental) representation of a specific set of subject matter is also important in influencing what sense viewers make of a diagram. The task of characterising relationships between the way a diagram is represented mentally and the effectiveness with which that diagram is processed poses novel challenges to researchers. This paper decribes some of these challenges and discusses methodologies that have been developed to explore the mental representation and processing of explanatory diagrams.