Investigating Visual Feedforward for Target Expansion Techniques
In Proceedings of the 33th international conference on Human factors in computing systems (CHI 2015). pages 2777-2786. 2015.
Target expansion techniques facilitate the pointing task by enlarging the effective sizes of targets. When the target expansion is applied to both the motor and visual spaces, the visual feedforward mechanism is key: Indeed it provides a visual aid to the user on the effective expanded targets prior to the execution or completion of the pointing task, enabling the user to take full advantage of the target expansion technique. Focusing on feedforward mechanisms, we introduce a design space that allows us to describe, classify and design target expansion techniques. To do so we first introduce and characterize the concept of atomic feedforward mechanism along three design axes. We then describe a target expansion technique as a combination of atomic feedforward mechanisms using a matrix-based notation. We provide an analytical exploration of the design space by classifying existing techniques and by designing six new techniques. We also provide a first experimental exploration of the design space in the context of distant pointing. The experimental protocol includes an innovative target layout for handling non-centroidal target expansion. The results show that feedforward dynamicity increases movement time and decreases subjective usability, while explicit expansion observability efficiently supports error prevention for distant pointing.