In an influential paper titled ''External cognition: how do graphical representations work?'', noted, amongst other things, three biases in work on graphical representations: that it has been primarily concerned with external representations which are not actively modified by the user (i.e. limited interactivity), it has ignored the role of social and communicative context (e.g. collaborative sketching), and it has not made progress toward a framework that might allow the designer to produce and evaluate new forms of graphical representation. They pointed out that ''little is known about the cognitive value of any graphical representations, be they good old-fashioned (e.g. diagrams) or more advanced (e.g. animations, multimedia, virtual reality)''. They argued for a theoretical approach that considers the role played by external representations in relation to internal mental ones: ''we need to ask what is the nature of the relationship between graphical representations and internal representations, and to consider how graphical representations are used when learning, solving problems and making inferences''.
Interest in expanding research on graphical representations into these areas prompted the Workshop on Interactive Graphical Communication at Queen Mary University of London in August 2000 and, developing out of that discussion this special issue. The papers collected here do not, jointly or individually, provide the kind of processing account that Scaife and Rogers argued was necessary for effective design. However, these papers do present empirical and theoretical progress in addressing several of the limitations they identified. They also present concepts and principles that provide a basis for engaging with the design of systems to support interactive graphical communication.