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All real-time computer games, particularly networked computer games, have a delay from when a player starts an action (e.g., clicking the mouse) until the game renders the result (e.g., firing a projectile). This delay can degrade both player performance (e.g., reduced game score) and quality of experience (e.g., the game is less fun). While previous work has studied the effects of delay on commercial games and individual game actions, a more detailed understanding is needed of the effects of delay on moving target selection with realistic target motion, a common scenario in many games. This paper presents an in-depth study of the effects of delay on the fundamental game action of selecting a moving target with a mouse while varying two parameters for the target motion - turn frequency and turn angle. We design and implement a custom game where players select moving targets using a mouse, while the game controls both the target motion and input delay. Analysis of data gathered in a 56-person user study shows both target selection time and accuracy degrade with delay. However, both selection time and accuracy increase with the frequency and angle of changes in the target's movement, because turning slows targets down even while making them less predictable. We set these results in the context of other studies of delay and target selection by comparing our findings to those in seven other previously published papers that investigated the effects of delay on target selection. [ABSTRACT FROM AUTHOR]

Many interfaces attempt to assist users by offering suggestions, predicting actions, or correcting user input. Although these attempts may often be beneficial, they will occasionally fail, and prior research from psychology and behavioral economics on loss aversion suggests that such failures may have an overweighted impact on subjective preferences. To better understand the relationship between interface outcomes and subjective preferences, we adapted to interaction a model from behavioral economics describing reference-dependent preferences. Two experiments examined our model's predictions: both involved word-snapping interface assistance during text selection, with subjects choosing whether they preferred unassisted text selection (no snapping) or assisted text selection (snapping). In Experiment 1, the word-snapping feature could be disabled when it was unhelpful by backtracking the selection, which required progress losses in terms of target characters selected. In Experiment 2, word-snapping could be disabled by pressing a modifier key and waiting for an animation to complete, without need for the loss of target characters. Time and error performance with both experimental methods were comparable. The model predicts an aversion to progress losses in Experiment 1 that should be neutralized in Experiment 2, and the results of both experiments conformed to these predictions. We discuss the implications of the model as a platform for understanding user preferences more broadly, especially when considering interfaces that risk periodically failing to meet user expectations. [ABSTRACT FROM AUTHOR]

Identifying a target command can be difficult and time-consuming when the user is unfamiliar with a software system. One technique for assisting command identification is to provide asubset interfacethat contains only a limited set of the system's capabilities. We examine the design of subset interfaces, showing that subsets can be presentedseparatelyto the full user interface (UI) (e.g. in a palette) orin place, with in-place methods using eitherstaticordynamicmethods to identify the subset. We introduce theStencilMapandEphemeralMapasin-placesubset UIs that, respectively, use static and dynamic highlighting. Both StencilMaps and EphemeralMaps make all of an application's commands concurrently available for selection within a grid. To highlight subset items StencilMaps use a static dark semi-transparent ‘stencil’ overlay to de-emphasise all but the subset items; EphemeralMaps, in contrast, use a short delay, with subset items shown immediately, and other items gradually faded in. A first experiment compares user performance with thein-placepresentation of StencilMaps against that of theseparatepresentation of a subset palette. Results confirm the predicted spatial memory benefits for StencilMaps. A second experiment analyses the performance impact of three approaches to highlighting: none,statichighlighting in StencilMaps, anddynamichighlighting in EphemeralMaps. Results show an interesting trade-off – while highlighting can offer benefits in assisting rapid target identification (particularly when the user is unfamiliar with the interface layout), there can also be longer-term performance benefits when highlighting is absent because the increased difficulty of visual search promotes the use and formation of spatial memory. [ABSTRACT FROM PUBLISHER]