In the blink of an eye: investigating latency perception during stylus interaction

While pen computing has become increasingly more popular, device responsiveness, or latency, still plagues such interaction. Although there have been advances in digitizer technology over the last few years, commercial end-to-end latencies are unfortunately similar to those found with touchscreens, i.e., 65 - 120 milliseconds. We report on a prototype stylus-enabled device, the High Performance Stylus System (HPSS), designed to display latencies as low as one millisecond while users ink or perform dragging tasks. To understand the role of latency while inking with a stylus, psychophysical just-noticeable difference experiments were conducted using the HPSS. While participants performed dragging and scribbling tasks, very low levels of latency could be discriminated, i.e., ~1 versus 2 milliseconds while dragging and ~7 versus 40 milliseconds while scribbling. The HPSS and our experimentation have provided further motivation for the implementation of latency saving measures in pen-based hardware and software systems.