An Evaluation of Stylus-based Text Entry Methods on Handheld Devices in Stationary and Mobile Scenarios
top
Although text entry in a mobile device has been heavily explored, most of the existing techniques have been studied only in a stationary scenario. Furthermore, we observed that the thumb of the non-dominant hand is available for the secondary input while a user is holding a device. Based on this observation, we designed a two-handed software keyboard with the stylus and the thumb. We compared four different stylus-based text entry techniques, including ours, in one stationary scenario and two mobile scenarios.
Introduction

Fig 1. A user is holding a PDA. Note that the thumb of the non-dominant hand holding the PDA
is available for simple manipulations on the screen.
Text entry is thus a basic interaction in the usage of PDAs, motivating the research and development of a broad range of
novel text input methods. Despite this already thorough exploration, we observe two opportunities for further investigation:
  • Most of the developed text entry techniques support input via only the userfs dominant hand. These techniques vary in input space, and thus leverage different motor skills. For example, the mini-qwerty keyboard requires users to click small keys, while a gesture-based text entry method requires users to gesture between a small number of larger-sized zones to input text. We observe however that when users hold a PDA with the non-dominant hand, the thumb of the non-dominant hand is available for secondary input (as shown in Fig 1). We believe that a two-handed keyboard can be designed to support simultaneous input through a stylus and the thumb of the non-dominant hand.
  • Most of the developed input techniques have been examined only while the user is stationary. However, mobile devices are used not only while the user is sitting or standing still, but also while she is walking. We believe that researchers also should investigate user text entry performance with various software keyboard designs for PDAs while users are actually mobile.
 
Two-handed Chorded Keyboard

Fig 2. Our two-handed chorded keyboard

After doing a pilot study with prototype designs, we had the design shown in Fig 2. The blue rectangle on the left-bottom of the screen represents the input region for the thumb of the non-dominant hand. A portion of the mini-qwerty keyboard is displayed on the right side of the screen. Initially, the interface shows the left portion of the mini-qwerty layout. The position of the thumb of the non-dominant hand in the blue region determines the portion of the mini-qwerty keyboard that should be displayed. For example, when the user places the thumb in the right-most region of the blue box, the right portion
of the mini-qwerty keyboard is shown, like in Fig 2 (c).

We did a comparative study with four different techniques, including ours, in one stationary scenario and two mobile scenarios. The study showed that mobility can impact the user performance in text entry and our design was the most accurate in the mobile scenarios. For the details, please see our paper.
Publication
  • Koji Yatani and Khai N. Truong (2007) "An Evaluation of Stylus-based Text Entry Methods on Handheld Devices in Stationary and Mobile Scenarios" In Proceedings of the nineth ACM SIGCHI International Conference on Human Computer Interaction with Mobile Devices & Services (MobileHCI 2007), pp. 145 -- 152, September 2007.