Spatial memory is an important facet of human cognition - it allows users to learn the locations of items over time and retrieve them with little effort. In human-computer interfaces, a strong knowledge of the spatial location of controls can enable a user to interact fluidly and efficiently, without needing to visually search for relevant controls. Computer interfaces should therefore be designed to provide support for developing the user's spatial memory, and they should allow the user to exploit it for rapid interaction whenever possible. However, existing systems offer varying support for...