Touching virtual objects in mid-air: a study on shape recognition

Mid-air haptic technology allows designers to build touchless interfaces incorporating tactile feedback. In the present study, 17 students of the University of Siena were engaged in an experiment where they had to recognize shapes (a circle, a square, or a point) presented one at a time as mid-air haptic stimuli. The task was to discriminate if a stimulus (e.g. round stimulus on the palm of the hand) was compatible with an image (e.g. a circle) or a word (e.g. "circle") displayed on a screen. The results indicate that only the "point"stimulus can lead to appreciable recognition performance, both in terms of accuracy and in relation to the time needed for the identification. No learning-based performance improvements were found. These results suggest that the haptic feedback provided by the mid-air technology used in the experiment is informative but difficult to discriminate and therefore it should be carefully designed in particular when associated to tasks requiring accuracy and speed of recognition.