Appropriateness of Foot Interaction for Non-Accurate Spatial Tasks Toni Pakkanen and Roope Raisamo Tampere Unit for Computer-Human Interaction (TAUCHI) Department of Computer Sciences, FIN-33014 University of Tampere {Toni.Pakkanen, Roope.Raisamo}@cs.uta.fi ABSTRACT This paper describes alternative methods for manipulating graphical user interfaces with a foot. Feet are used in many real world tasks together with the rest of the body, but in computer environments they are almost completely put aside as an interaction possibility. One of the major problems in choosing input methods for different tasks in user interfaces is determining what kind of method is appropriate for a certain task. Feet could easily be used as a supportive input method in interaction with computers together with the traditional mouse. In this paper, we discuss the possibility of using foot input in different non- accurate spatial tasks, and the efficiency and usability experience the users have of foot interaction compared with a traditional hand-based interface with the same input device. The aim is to find out how well foot interaction suits for non-accurate spatial tasks. Categories & Subject Descriptors: H5.2. [Information Interfaces and Presentation]: User Interfaces – Interaction styles, input devices and strategies, evaluation/methodology; I3.6. [Computer Graphics]: Methodology and Techniques – Interaction techniques General Terms: Experimentation; Human Factors; Measurement. Keywords: Input; Interaction; Multimodality; Usability. INTRODUCTION Computers are mostly operated today by using spatial interaction methods with a mouse, i.e., objects are moved, resized and selected with a mouse. Several of these tasks interrupt users’ workflow with information. For example, when a user is reading a webpage or writing a document, the window has to be scrolled every so often and this is usually done with a mouse. Currently this part of the task can be done separately with a mouse wheel, which is an example of how tasks can be divided into different subtasks that can be done simultaneously. Some of these supportive non-accurate subtasks could also be executed by foot without any interruptions to current workflow. For example, while writing the use of the mouse wheel requires interrupting the writing task. If these kinds of subtasks would be operated with a foot, users could keep their concentration on the work they are doing and workflow would not be interrupted. Currently, feet are mostly used in expensive virtual environments as an additional input method [4], but for example a trackball could be a cheap additional input device to be used by feet and it would provide the users with a less interruptive way to handle supportive subtasks like scrolling or moving objects in their document. The factors limiting interaction possibilities with feet are human capabilities to operate conveniently, efficiently and accurately enough, i.e., human cognitive and psychomotor capabilities and users’ subjective experiences of the interaction method. Generally, this means simpler tasks, and easier input methods mean more efficient and more accurate input results. Fitts’ law and its derivatives [5] have in many cases been proven to fit in measuring human psychomotor capabilities, but no form of the law takes into account a user’s subjective experience of an input method. This leads to a situation where the law describes the efficiency of an input method, but an efficient input method is not necessarily preferred by the users only because of its efficiency. The subjective satisfaction of an input method strongly affects which input methods the users prefer. In several studies based on Fitts’ law [e.g., 5, 3] it has been shown that the non-dominant hand and feet are in psychomotor aspect less effective than the primary hand. The order of the efficiency of input limbs is the dominant hand, the non-dominant hand, the dominant foot and the non-dominant foot. Feet have been used as an alternative method for the hand [6, 7], but it has been proven that foot interaction is suffering more in execution times with accurate tasks than the hands, so hands are better suited for accurate subtasks and the hands are also about twice as accurate as the feet [3]. In human cognitive processing the question is how to divide the subtasks so that users do not have to do several primary tasks at once. With the primary task we mean tasks that require the user’s attention and that way cause more cognitive load to the user. In psychological research it has been shown that humans are capable of efficient parallel Copyright is held by the author/owner(s). CHI 2004, April 24–29, 2004, Vienna, Austria. ACM 1-58113-703-6/04/0004. CHI 2004 ׀Late Breaking Results Paper 24-29 April ׀Vienna, Austria 1123