Consistency vs. Multiplicity in Interface Design:
Limitations of Single Interface Metaphors

Liang-Yi Lin

James A. Levin

University of Illinois at Urbana-Champaign
Champaign, IL 61820


Many prescriptive interface design guides stress the importance of consistency in interface design, so that novice users are not confused and can learn new applications more quickly. While agreeing that consistency is generally a good thing, this paper presents research that shows some of the limitations of consistency. The first experiment points to the task specific value of single interface models. Subjects using any one of three interface models (book, note card, map) did well on certain tasks and more poorly on others. There was a strong interaction between the type of interface and the type of task the subjects were given. The second and third experiments explored the acquisition of skill in using multiple interfaces vs. a single interface. Subjects learning a single interface initially outperformed the subjects learning three interfaces. However, the consistent interface subjects' performance topped out, and there was a cross-over point after extended use of the interfaces, after which the multiple-interface subjects outperformed the single-interface subjects. They showed more cognitive flexibility, choosing the interface that was appropriate for each task they were faced with. Consistency produced a fast learning curve, but also limited the level of expertise that users achieved.

Topic areas: interface design, user models, design principles

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