Effects of Holding Ring Attached to Mobile Devices on Pointing Accuracy Yuya Kawabata, Daisuke Komoriya, Yuki Kubo, Buntarou Shizuki, and Jiro Tanaka University of Tsukuba, Japan {kawabata,komoriya,kubo,shizuki,jiro}@iplab.cs.tsukuba.ac.jp Abstract. It is difficult for a user to operate a touch screen device accurately under the eyes-free condition. The difficulties arise from the absence of visual or tactile feedback under this condition. This research focuses on the effective- ness of a holding ring attached to the back of mobile devices to improve pointing accuracy under the eyes-free condition. We explored the extent to which the hold- ing ring improves the pointing accuracy by preparing three mobile devices with holding rings attached in different positions and a mobile device without a hold- ing ring. The pointing accuracy was then evaluated by performing user studies. The result suggested that the pointing accuracy could be improved under the tar- get condition, which is 15.4 mm × 10.4 mm, by attaching the holding ring. Keywords: Eyes-free input · Back-of-device interaction · Tactile feedback · One-handed operation · Touch screen · Smartphone · Thumb-based input 1 Introduction Using a mobile device with a touch screen (hereafter a mobile device) while walking has emerged as a social problem, because it consumes the user’s visual attention and thus, causes of traffic accidents [1, 2]. One of the solutions to this problem is an eyes- free touch input which enables the user to operate the mobile device without watching the display of the device. However, it is difficult to operate a mobile device without being able to look at the display [3] because there is neither visual nor tactile feedback. Our idea to address the above issue was prompted by a previous solution and re- search. The user of a one-handed keyboard (e.g., Twiddler Tek Gear Inc.) uses a belt to hold the keyboard stably. Fukatsu et al. [4] and Corsten et al. [5] showed that the point- ing accuracy in eyes-free touch input is improved by tactile landmarks on the back of the device. These solutions and research results suggest that the back of a device presents potential design space for improving the performance of the input via the touch screen located on the front of a mobile device.