Gesture output: eyes-free output using a force feedback touch surface

We propose using spatial gestures not only for input but also for output. Analogous to gesture input, the proposed gesture output moves the user's finger in a gesture, which the user then recognizes. We use our concept in a mobile scenario where a motion path forming a "5" informs users about new emails, or a heart-shaped path serves as a mes- sage from a friend. We built two prototypes: (1) The long- RangeOuija is a stationary prototype that offers a motion range of up to 4cm; (2) The pocketOuija is self-contained mobile device based on an iPhone with up to 1cm motion range. Both devices actuate the user's fingers by means of an actuated transparent foil overlaid onto a touchscreen. We conducted three studies with the longRangeOuija in which participants recognized 2cm marks with 97% accu- racy, Graffiti digits with 98.8%, pairs of Graffiti digits with 90.5%, and Graffiti letters with 93.4%. Participants previ- ously unfamiliar with Graffiti identified 96.2% of digits and 76.4% of letters, suggesting that properly designed gesture output is guessable. After the experiment, the same participants were able to enter 100% of Graffiti digits by heart and 92.2% of letters. This suggests that participants learned gesture input as a side effect of using gesture output on our prototypes.