Human On-Line Response to Visual and Motor Target Expansion

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 overtarget 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.

Faster Cascading Menu Selections with Enlarged Activation Areas

Cascading menus are used in almost all graphical user interfaces. Most current cascade widgets implement an explicit delay between the cursor entering/leaving a parent cascade menu item and posting/unposting the associated menu. The delay allows users to make small steering errors while dragging across items, and it allows optimal diagonal paths from parent to cascade items. However, the delay slows the pace of interaction for users who wait for the delay to expire, and it demands jerky discrete movements for experts who wish to pre-empt the delay by clicking. This paper describes Enlarged activation area MenUs (EMUs), which have two features: first, they increase the area of the parent menu associated with each cascade; second, they eliminate the posting and unposting delay. An evaluation shows that EMUs allow cascade items to be selected up to 29% faster than traditional menus, without harming top-level item selection times. They also have a positive smoothing effect on menu selections, allowing continuous sweeping selections in contrast to discrete movements that are punctuated with clicks.

Multimodal feedback for the acquisition of small targets

This paper examines how multimodal feedback assists target acquisition in graphical user interfaces. All combinations of three feedback modes are analysed: non-speech audio, tactile, and pseudo-haptic 'sticky' feedback. The tactile conditions used stimulation through vibration (rather than force-feedback), and the sticky conditions were implemented by dynamically reconfiguring mouse control-display gain as the cursor entered the target. Results show that for small, discretely located targets all feedback modes reduce targeting times, with stickiness providing substantial improvements. Furthermore, stickiness and tactile appear to combine well. However, the results of a more ecologically-oriented menu-selection task show the need for caution, revealing that excessive feedback can damage interaction though 'noise' that interferes with the acquisition of neighbouring targets.

On the Validity of Using First-Person Shooters for Fitts' Law Studies

3D first-person shooter games provide highly polished, compelling and entertaining environments that far out-strip the refinement of most research systems. Many also provide extensive support for tailoring the environment, allowing researchers to adapt them to specific research agendas. This paper examines using 3D first-person shooter game environments for motivating participants in Fitts' Law studies. In particular, we examine whether the first-person metaphor for target acquisition, which involves rotating the world to pan the target to the screen-centre, is accurately modelled by Fitts' Law, and whether the resultant Fitts' metrics are representative of traditional cursor-based acquisition. Results show excellent Fitts' modelling, with metrics that are similar to traditional pointing.

Improving the Acquisition of Small Targets

This paper describes the design and comparative evaluation of three methods that aid the acquisition of small targets. The first method, called 'bubble targets', increases the effective width of the target as the pointer approaches. The second method uses a form of 'stickyness' to restrict movement as the pointer passes over an object. In the third method, called 'goal-crossing', the user simultaneously presses two mouse buttons before passing the pointer over the item. Goal-crossing overcomes the need for the user to decelerate the mouse when acquiring the target. Two evaluations were conducted, with the first (n=37) based on the acquisition of abstract targets for Fittst Law modelling, and the second based on an ecologically oriented window resizing task (n=11). Both showed that goal-crossing allowed the fastest target acquisition, but that it produced high error rates and was unpopular with participants. The 'bubble' and 'sticky' techniques also allowed faster target acquisition than the traditional approach, and users were enthusiastic about them. Fitts' Law accurately modelled all techniques. Implications of the results for general user interface design are briefly discussed.