Exploration Strategies for Tactile Graphics Displayed by Electrovibration on a Touchscreen

Abstract

Advancements in surface haptics technology have given rise to the development of interactive applications displaying tactile content on touch surfaces such as images, signs, diagrams, plots, charts, graphs, maps, networks, and tables. In those applications, users manually explore the touch surface to interact with the tactile data using some intuitive strategies. The user's exploration strategy, tactile data's complexity, and tactile rendering method all affect the user's haptic perception, which plays a critical role in design and prototyping of those applications. In this study, we conducted experiments with human participants to investigate the recognition rate and time of five tactile shapes (i.e., triangle, square, pentagon, hexagon, and octagon) rendered by electrovibration on a touchscreen using three different methods and displayed in prototypical orientation and non-prototypical orientations (i.e., 15 degrees CW and CCW to the prototypical orientation). The results showed that the correct recognition rate of the shapes was higher when the haptically active area (area where electrovibration was on) was larger. However, as the number of edges was increased, the recognition time increased and the recognition rate dropped significantly, arriving to a value slightly higher than the chance rate of 20% for non-prototypical octagon. Moreover, the recognition time for inside rendering condition was significantly shorter in comparison with edge and outside rendering conditions and edge rendering condition led to the longest recognition time. We also recorded the participants' finger movements on the touchscreen to examine their haptic exploration strategies. Based on our temporal analysis, we classified six exploration strategies adopted by participants to identify the shapes, which were different for the prototypical and non-prototypical shapes. Moreover, our spatial analysis revealed that the participants first used