ABSTRACT

Search and Selection In Vast and Splay Menus

By

Ben D. Harper

Thesis submitted to the Faculty of the Graduate School of the University of Maryland in partial fulfillment of the requirements for the degree of

Masters of science

1995

Advisory Committee:

Associate Professor, Dr. Kent L. Norman Ph.D.

Professor, Dr. Nancy S. Anderson Ph.D.

Associate Professor, Dr. Gary Marchionini Ph.D.

Splay menus use a technique that allows a large number of menu items to be displayed in a single screen while maintaining depth and breadth information. The advantage of splay menus is that final goal items can be reached in one selection, instead of the large number of mouse movements required in traditional menus. The challenge in splay menus is to present the options on screen in a format that aids visual search in a vast selection space. This study explores factors that affect selection in broad menu structures. It demonstrates how a splay menu structure can be made optimal for an item set as large as 256 items. By shifting the search task from conjunction reliant character searches to feature searches using color, users more quickly and accurately make selections in large menu systems. Also of interest was the effect of input device (graphics tablet or mouse)on selection. Grouping cues using eight colors were compared to text grouping cues with row, column, and block group formats. Results show speed, latency, and fatigue advantages for color grouping cues in all conditions. Grouping cue and form interacted in both speed of selection and movement latency. The main effects of both cue and form with respect to fatigue level were significant also. Surprisingly, error rates in selection for all conditions was very low. Subjects did not show any learning effects over the course of 384 selections suggesting that these effects are not diminished over time. Input device showed no effect on any measure. The advantageous effect of color grouping cues support the Wolfe, et al. theory of guided attention in which pre-attentively processed cues guide attentive searches to locations most likely to contain the target. A distinction between group search and item search in this task is suggested by both the differential finding of speed and motion latency and the positive correlation of these two measures. A number of practical implications of these finding in screen layout and menu design are discussed.

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