Abstract
The components of graphical user interfaces can be made to dynamically expand as the cursor approaches, providing visually appealing effects. Expansion can be implemented in a variety of ways: in some cases the targets expand visually while maintaining a constant smaller motor-space for selection; and in others both the visual and motor-spaces of the objects are enlarged. Previous research by McGuffin & Balakrishnan [15], and confirmed by Zhai et al. [19], has shown that enlarged motor-space expansion improves acquisition performance. It remains unclear, however, what proportion of the performance improvement is due to the enlarged motor-space, and what to the confirmation of the over-target state provided by visual expansion. We report on two experiments which indicate that for small targets, visual expansion in unaltered motor-space results in similar performance gains to enlarged motor-spaces. These experiments are based on tasks where users are unable to anticipate the behaviour of the targets. Implications for commercial use of visual expansion in unaltered motor-space are discussed.
