Providing Semi-private Feedback on a Shared Public Screen by Controlling Presentation Onset

We describe a novel technique to provide semi-private feedback on a shared public screen. The technique uses a no-onset presentation that takes advantage of perceptual limitations in human vision to avoid alerting other users to feedback directed at one individual user by suppressing the sudden onset of the feedback. Three experiments evaluated the effectiveness of the technique and appropriate timing parameters and alternatives for presentation onset. Our experiments indicated that an 80 ms no-onset presentation allows participants to interpret information directed to them with over 90% accuracy, but their ability to interpret simultaneously presented information intended for others will be close to random chance. The technique initially camouflages the information being presented by overlaying additional visual elements and then removes those elements to reveal only the elements encoding the information being presented. We discuss applications for the technique, including classroom clicker usage, which was our original motivation for the study.