This chapter presents a number of software applications that make use of an eye tracker. It builds on the knowledge of visual attention and its control mechanisms as presented in chapters 3 and 5. It provides a tour through the years, showing how the use of eye gaze as indicator of visual attention has developed from being an additional input modality, supporting the disambiguation of fuzzy signals, to an interaction enhancement technique that allows software systems to work proactively and retrieve information without the user giving explicit commands.

Introduction

Our environment provides far more perceptual information than can be effectively processed. Hence, the ability to focus our attention on the essential is a crucial skill in a world full of visual stimuli. What we see is determined by what we attend to: the direction of our eye gaze, the focus of our visual attention, has a close relationship with the focus of our attention.

Eye trackers, which are used to measure the point of gaze, have developed rapidly during recent years. The history of eye-tracking equipment is long. For decades, eye trackers have been used as diagnostic equipment in medical laboratories and to enable and help communication with severely disabled people (see, e.g., Majaranta and Räihä 2007). Only recently have eye trackers reached the level of development where they can be considered as input devices for commonly used computing systems.