In this paper we present our findings from a lab and a field study investigating how passers-by notice the interactivity of public displays. We designed an interactive installation that uses visual feedback to the incidental movements of passersby to communicate its interactivity. The lab study reveals:(1) Mirrored user silhouettes and images are more effective than avatar-like representations. (2) It takes time to notice the interactivity (approximately 1.2s). In the field study, three displays were installed during three weeks in shop windows, and data about 502 interaction sessions were collected. Our observations show: (1) Significantly more passers-by interact when immediately showing the mirrored user image (+90%) or silhouette (+47%) compared to a traditional attract sequence with call-to-action. (2) Passers-by often notice interactivity late and have to walk back to interact (the landing effect). (3) If somebody is already interacting, others begin interaction behind the ones already interacting, forming multiple rows (the honeypot effect). Our findings can be used to design public display applications and shop windows that more effectively communicate interactivity to passers-by.

Abstract. Distant displays such as interactive public displays (IPD) or interactive television (ITV) require new interaction techniques as traditional input devices may be limited or missing in these contexts. Free hand interaction, as sensed with computer vision techniques, presents a promising interaction technique. This paper presents the adaptation of three menu techniques for free hand interaction: Linear menu, Marking menu and FingerCount menu. The first study based on a Wizard-of-Oz protocol focuses on Finger-Counting postures in front of interactive television and public displays. It reveals that participants do not choose the most efficient gestures neither before nor after the experiment. Results are used to develop a Finger-Count recognizer. The second experiment shows that all techniques achieve satisfactory accuracy. It also shows that Finger-Count requires more mental demand than other techniques.

Figure 1. a,b,c) Three strategies for revealing an initial mid-air gesture on public displays: a) spatial division, b) temporal division, c) integration; d,e,f) examples of findings from our field study: d) the Teapot Gesture is fluently integrated with other gestures, e) users explore a potential gesture vocabulary, f) users often imitate other users' gestures. ABSTRACTWe investigate how to reveal an initial mid-air gesture on interactive public displays. This initial gesture can serve as gesture registration for advanced operations. We propose three strategies to reveal the initial gesture: spatial division, temporal division, and integration. Spatial division permanently shows the gesture on a dedicated screen area. Temporal division interrupts the application to reveal the gesture. Integration embeds gesture hints directly in the application. We also propose a novel initial gesture called Teapot to illustrate our strategies. Our main findings from a laboratory and field study are: A large percentage of all users execute the gesture, especially with spatial division (56%). Users intuitively discover a gesture vocabulary by exploring variations of the Teapot gesture by themselves, as well as by imitating and extending other users' variations.