Modern computer systems routinely present information to the user as a combination of text and diagrammatic images, described as “graphical user interfaces”. Practitioners and researchers in Human-Computer Interaction (HCI) generally believe that the value of these diagrammatic representations is derived from metaphorical reasoning; they communicate abstract information by depicting a physical situation from which the abstractions can be inferred.
This assumption has been prevalent in HCI research for over 20 years, but has seldom been tested experimentally. This thesis analyses the reasons why diagrams are believed to assist with abstract reasoning. It then presents the results of a series of experiments testing the contribution of metaphor to comprehension, problem solving, explanation and memory tasks carried out using a range of different diagrams.
The results indicate that explicit metaphors provide surprisingly little benefit for cognitive tasks using diagrams as an external representation. The benefits are certainly small compared to the effects of general expertise in performing computational tasks. Furthermore, the benefit of metaphor in diagram use is largely restricted to mnemonic assistance. This mnemonic effect appears to be greatest when the user of the diagram constructs his or her own metaphor, rather than being presented with a systematic metaphor of the type recommended for use in HCI.