48 Improving Browsing Performance: A study of four input devices for scrolling and pointing tasks Shu min Zhai Barton A. Smith Ted Selker IBM Almaden Research Center 650 Harry Road, NWE-B2, San Jose, California 95120, USA {zhai, smith, selker}@almaden.ibm.com ABSTRACT Navigating through online documents has become an increasingly common HeI task. This paper investigates alternative methods to improve user performance for browsing World Wide Web and other documents. In a task that involved both scrolling and pointing, we compared three input methods against the status-quo. The results showed that a mouse with a fmger wheel did not improve user's performance; two other methods, namely a mouse with an isometric rate-control joystick operated by the same hand and a two handed system that put a mouse on the dominant hand and a joystick on the other, both significantly improved users' performance. A human factors analysis on each of the three input methods is also presented. KEYWORDS Input Devices, Interaction Techniques, Web Browsing, Scrolling, Mouse, Isometric vs. Isotonic Devices, joystick, Wheel Mouse, IntelliMouse lM , TrackpointlIPM, Two-handed Input, Bimanual Interaction. 1. INTRODUCTION Today's mainstream interaction style (WIMP - window, icon, menu and pointer), although with a long history (Smith, Irby, Kimball, Verplank & Harslem, 1982), is still gaining a wider range of applications and a larger user population. The rapidly developing World Wide Web (WWW)makestheuse of such style of interaction even more frequent and intense. As a result, the limita- tions of existing WIMP features also become more severe and obvious. There have been numerous interface inventions and studies since the basic WIMP style was developed (e.g Buxton 1986), but they have been largely restricted to the research literature and isolated demonstrations. The unavailability of commercial hardware and software and an incomplete understanding of human factors both have contributed to the lack of major improvements in the mainstream interfaces. One basic feature of the existing mainstream WIMP interfaces is that the user communicates with the computer system via a single stream of spatial input, physically driven by a 2 degree of freedom input device, typically a mouse, and graphically displayed as a cursor. The universal cursor travels around the entire interface, switching its functions from pointing, to selection, to drawing, to scrolling, to opening and to jumping, according to what virtual devices (widgets), such as the main document/window, a menu, a scrolling bar, an icon or a hyperlink, has been acquired and engaged. Such a single stream operation, needless to say, has offered the users many advantages such as the ease of understanding and learning the interaction mechanism. The disadvantage, however, is the limited communication bandwidth (Buxton 1986) and the costs in time and cognitive effort of acquiring widgets and control points (Buxton and Myers 1986, Leganchuk, Zhai and Buxton 1996). A particular case at point is document browsing, one of the most frequent tasks in interacting with computers. A document, such as a text file, a spreadsheet, a folder, and most importantly, a Human-Computer Interaction: INTERACT'97 S. Howard, J. Hammond & G. Lindgaard (editors) Published by Chapman & HaIl ©IFIP 1997