Evaluating Temporal Delays and Spatial Gaps in Overshoot-avoiding Mouse-pointing Operations

For hover-based UIs (e.g., pop-up windows) and scrollable UIs, we investigated mouse-pointing performance for users trying to avoid overshooting a target while aiming for it. Three experiments were conducted with a 1D pointing task in which overshooting was accepted (a) within a temporal delay, (b) via a spatial gap between the target and an unintended item, and (c) with both a delay and a gap. We found that, in general, movement times tended to increase with a shorter delay and a smaller gap if these parameters were independently tested. Therefore, Fitts’ law cannot accurately predict the movement times when various values of delay and/or gap are used. We found that 800 ms is required to remove negative effects of distractor for densely arranged targets, but we found no optimal gap.