From Brains to Branch Points:
Cognitive Constraints in Navigational Design

Abstract

This work develops an applied design theory of navigation¾the task of determining where places and things are, how to get to them and actually getting there¾intended to support the analytical and generative phases of the design of electronic user interfaces. It develops a model of navigation as a fundamental cognitive task comprising four subtasks, a taxonomy of navigational design comprising six subdomains, and a set of fifteen design principles to aid in developing environmental locomotional design (a subdomain of navigational design) in support of wayfinding (a subtask of navigation). The principles link specific manipulations of design elements to potential effects on wayfinding performance, and represent constraints imposed by wayfinding cognition on environmental locomotional design. Twelve of the principles are derived from existing psychological evidence, while three are hypothesized to account for incongruities between the psychological evidence and empirical results.

The design principles are applied to two design examples: a design for everyday file system interaction in a traditional desktop environment, and a design for inter-object navigation in a spatial multiscale environment. The latter design is partially implemented and subject to user testing. Results show an average reduction in time on task of 30% on a directed search task. Performance increases were accompanied by reductions in measures of effort, such as mouse movement, of up to 84%. Overall, the data imply that the design manipulations suggested by the design principles reduced the cognitive overhead of wayfinding, as anticipated.

The work illustrates how design knowledge, in the context of user interface design, differs from psychological knowledge, and offers a process for extracting the former from the latter. It also shows that existing psychological knowledge is insufficient for design needs, and speculates that this is not merely a matter of quantity, but may also be due to differences in disciplinary needs.

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