This dissertation studies the roles and effects of visual affordances and feedback in a general-purpose gesture interface for novice users. Gesture interfaces are popularly viewed as intuitive and user-friendly modes of interacting with computers and robots, but they in fact introduce many challenges for users not already familiar with the system. Affordances and feedback – two fundamental building blocks of interface design – are perfectly suited to address the most important challenges and questions for novices using a gesture interface: what can they do? how do they do it? are they being understood? has anything gone wrong? Yet gesture interfaces rarely incorporate these features in a deliberate manner, and there are presently no well-adopted guidelines for designing affordances and feedback for gesture interaction, nor any clear understanding of their effects on such an interaction.
A general-purpose gesture interaction system was developed based on a virtual touchscreen paradigm, and guided by a novel gesture interaction framework. This framework clarifies the relationship between gesture interfaces and the application interfaces they support, and it provides guidance for selecting and designing appropriate affordances and feedback. Using this gesture system, a 40-person (all novices) user study was conducted to evaluate the effects on interaction performance and user satisfaction of four categories of affordances and feedback. The experimental results demonstrated that affordances indicating how to do something in a gesture interaction are more important to interaction performance than affordances indicating what can be done, and also that system status is more important than feedback acknowledging user actions. However, the experiments also showed unexpectedly high interaction performance when affordances and feedback were omitted. The explanation for this result remains an open question, though several potential causes are analyzed, and a tentative interpretation is provided.
The main contributions of this dissertation to the HRI and HCI research communities are 1) the design of a virtual touchscreen-based interface for general-purpose gesture interaction, to serve as a case study for identifying and designing affordances and feedback for gesture interfaces; 2) the method and surprising results of an evaluation of distinct affordance and feedback categories, in particular their effects on a gesture interaction with novice users; and 3) a set of guidelines and insights about the relationship between a user, a gesture interface, and a generic application interface, centered on a novel interaction framework that may be used to design and study other gesture systems. In addition to the intellectual contributions, this work is useful to the general public because it may influence how future assistive robots are designed to interact with people in various settings including search and rescue, healthcare and elderly care
