Understanding and Exploiting Spatial Memory in the Design of Efficient Command Selection Interfaces

Humans have a strong natural ability to remember item locations. In graphical user interfaces, this ability is one of the primary mechanisms by which users become efficient. However, there are two ways in which modern applications often fail to exploit the potential of spatial memory. First, they overuse hierarchical structures such as cascading menus, which slows down interaction for expert users who already know item locations; and second, they move items around, most commonly in response to changing display geometry. The three goals of this thesis are therefore to (1) develop a better understanding of human spatial memory in the context of user interfaces; (2) design and validate efficient command-selection interfaces based on the strength of spatial memory; and (3) design and validate interface strategies that allow users to maintain spatial memory even when display geometry changes. Addressing goal (1), a comprehensive literature review of spatial memory for user interfaces is presented. The review covers underlying psychological models of spatial memory, the observable properties of spatial memory, and existing applications of spatial memory to human-computer interaction. In addition to informing the research in this thesis, the review is intended to provide a useful summary of the state of spatial memory research for scientists in HCI, as well as providing a set of design guidelines on spatial memory for practitioners. Addressing goal (2), this thesis presents the design and evaluation of two related user interface techniques, CommandMaps and StencilMaps. The CommandMap is a spatially stable interface with a flattened hierarchy, intended as a replacement for cascading menu systems. Theoretical performance predictions indicate that CommandMaps should be significantly faster than traditional user interfaces such as menus and the Microsoft Office Ribbon, and laboratory-based empirical studies of command selection confirm these predictions. These positive results motivated the design and implementation of two real-world CommandMap user interfaces based on Microsoft Word and Pinta (an open-source image editing application). Evaluation results confirmed that CommandMaps continue