Acquisition of expanding targets

TLDR

Several UI widgets dynamically grow in size when focused, such as toolbar icons that expand to aid selection while keeping a small initial size to save screen space, but this reduced initial size can degrade selection performance. The study investigates how varying expansion parameters affect selection performance in a task. The experiment varied expansion parameters and measured selection performance in a controlled task. Results show that Fitts' law predicts performance, which depends on the target's final size rather than its initial size, even when expansion starts late, indicating expanding widgets can be used without sacrificing performance.

Abstract

There exist several user interface widgets that dynamically grow in size in response to the user's focus of attention. Some of these, such as icons in toolbars, expand to facilitate their selection - allowing for a reduced initial size in an attempt to optimize screen space use. However, selection performance may be degraded by this decreased initial widget size. We describe an experiment which explores the effects of varying parameters of expansion techniques in a selection task. Our results suggest that Fitts' law can model and predict performance in such tasks. They also indicate that performance is governed by the target's final size, not its initial one. Further, performance is dependent on the target's final size even when the target only begins expanding as late as after 90% of the movement towards the target has already been completed. These results indicate that expanding widgets can be used without sacrificing performance