The effect of contrast design of virtual keyboard in smartphones on touch behavior and usability in text input

Abstract

Background Virtual keyboards in smartphones provide a variety of design themes that allow users to customize their keyboard design. However, indiscreet provision and application of design themes for virtual keyboards can degrade the performance of text input. In this study, we investigated how the contrast design between the background color and the button color of the virtual keyboard affects the user's touch behavior and performance during text input. Methods For the purpose, we have developed an experimental app that can perform text input with one of five different contrast designs (WW, WG, GB, GG, and NB) in virtual keyboard. The app automatically recorded the usability and touch point data during text input. Participants performed the task of inputting given sentences quickly without any typos by using five virtual keyboards in random order. Results Experimental results showed that the contrast between the background and the buttons of the virtual keyboard influenced the speed and satisfaction of the text input. Furthermore, according to the contrast design, the size of the Y-axis shift or distribution of the touch point has also changed. Collectively, the WW keyboard (white button on a light gray background), which is the most common design and has the same contrast as iPhone's default keyboard, was the best in typing speed and subjective satisfaction. On the other hand, the design that is difficult to distinguish between background and buttons (NB keyboard, no contrast) has had a very negative impact on typing speed and satisfaction. Conclusions The contrast between the background and buttons of a virtual keyboard is not only a matter of aesthetic design but can also affect touch behavior and text input usability. Smartphone and application makers have to make a careful decision about the default contrast of virtual keyboards.