Finger Placement and Hand Grasp during Smartphone Interaction

Abstract

Smartphones are currently the most successful mobile devices. Through their touchscreens, they combine input and output in a single interface. A body of work investigated interaction beyond direct touch. In particular, previous work proposed using the device's rear as an interaction surface and the grip of the hands that hold the device as a means of input. While previous work provides a categorization of grip styles, a detailed understanding of the preferred fingers' position during different tasks is missing. This understanding is needed to develop ergonomic grasp-based and Back-of-Device interaction techniques. We report from a study to understand users' finger position during three representative tasks. We highlight the areas that are already covered by the users' hands while using the on-screen keyboard, reading a text, and watching a video. Furthermore, we present the position of each of the user's fingers during these tasks. From the results, we derive interaction possibilities from an ergonomic perspective.