External representations are involved in many cognitive tasks, such as multiplication with
paper and pencil, grocery shopping with a written list, geometrical problem solving, graph
understanding, diagrammatic reasoning, chess playing, and so on. Few would deny that
external representations play certain roles in these tasks. However, in comparison with
internal representations, relatively little research has been directed towards the nature of
external representations in cognition. This might be due to the belief that very little knowledge about the internal mind can be gained by studying external representations, or due to
the view that external representations are nothing but inputs and stimuli to the internal
mind, or simply due to the lack of a suitable methodology for studying external representations.