CHI ‘88 AN EMPIRICAL COMPARISON OF PIE vs. LINEAR MENUS Jack Callahan, Don Hopkins, Mark Weisert and Ben Shneiderman Computer Science Department University of Maryland College Park, Maryland 20742 ABSTRACT Menus are largely formatted in a linear fashion listing items from the top to bottom of the screen or win- dow. Pull down menus are a common example of this format. Bitmapped computer displays, however, al- low greater freedom in the placement, font, and gen- eral presentation of menus. A pie menu is a format where the items are placed along the circumference of a circle at equal radial distances from the center. Pie menus gain over traditional linear menus by reducing target seek time, lowering error rates by fixing the dis- tance factor and increasing the target size in Fitts’s Law, minimizing the drift distance after target selec- tion, and are, in general, subjectively equivalent to the linear style. KEYWORDS: menus, user interface, empirical stud- ies, directional selection INTRODUCTION In presenting a list of choices to the user, most com- puter system designers have been limited, largely by the available hardware and software, to a linear for- mat. The items are listed from top to bottom, some- times with an index number for each to the item. OC- casionally, the lists are multi-columned, have multiple items per line, or are even hierarchical (i.e. indented sub-choices), but for the most part lie in a strictly one dimensional structure. hlany of these menus are static on the display screen or activated from mouse Supported in part by the Xerox Corporation Univer- sity Grants Program, NSF grant #DCR-8219507, and Office of Naval Research grant #N00014-87-K-0307. t Computer Science Laboratory, Xerox PARC, Palo Alto, Calif. 94303. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage,the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. 01988 ACM-O-89791-265-9/88/0004/0095 $00.75 Login Logout Open Close Shape Move I Figure 1: A typical linear menu Login Move Shrink Open 0 Close @ Shape I Logout Figure 2: A crude pie menu actions in two formats: pull-down (menu appears at a fixed label on screen when mouse directed) or pop-up (menu appears anywhere within a fixed area, occasion- ally the whole screen) [ll]. Some systems have used the two dimensional nature of the computer display to the advantage of certain menu applications. Many flight simulation programs, for example, lay out direc- tional headings in a typical compass format. Item placement in menus has been an important re- search topic for many years. Menu organization is typically divided into three types [4]: alpha/numeric, categorical (functional), and random ordering. It is generally agreed that the performance of subjects (i.e. time to seek a target) with different placement styles converges with practice [2,10]. Further studies [9] re- vealed that a functional placement of items is supe- 95