Michael Dorr

n/a

A less studied component of gaze allocation in dynamic real-world scenes is the time lag of eye movements in responding to dynamic attention-capturing events. Despite the vast amount of research on anticipatory gaze behaviour in natural situations, such as action execution and observation, little is known about the predictive nature of eye movements when viewing different types of natural or realistic scene sequences. In the present study, we quantify the degree of anticipation during the free viewing of dynamic natural scenes. The cross-correlation analysis of image-based saliency maps with an empirical saliency measure derived from eye movement data reveals the existence of predictive mechanisms responsible for a near-zero average lag between dynamic changes of the environment and the responding eye movements. We also show that the degree of anticipation is reduced when moving away from natural scenes by introducing camera motion, jump cuts, and film-editing.

Contrast sensitivity has been extensively studied over the last decades and there are well-established models of early vision that were derived by presenting the visual system with synthetic stimuli such as sine-wave gratings near threshold contrasts. Natural scenes, however, contain a much wider distribution of orientations, spatial frequencies, and both luminance and contrast values. Furthermore, humans typically move their eyes two to three times per second under natural viewing conditions, but most laboratory experiments require subjects to maintain central fixation. We here describe a gaze-contingent display capable of performing real-time contrast modulations of video in retinal coordinates, thus allowing us to study contrast sensitivity when dynamically viewing dynamic scenes. Our system is based on a Laplacian pyramid for each frame that efficiently represents individual frequency bands. Each output pixel is then computed as a locally weighted sum of pyramid levels to introduce local contrast changes as a function of gaze. Our GPU implementation achieves real-time performance with more than 100 fps on high-resolution video (1920 by 1080 pixels) and a synthesis latency of only 1.5 ms. Psychophysical data show that contrast sensitivity is greatly decreased in natural videos and under dynamic viewing conditions. Synthetic stimuli therefore only poorly characterize natural vision.

Open-source eye trackers have the potential to bring gaze-controlled applications to a wider audience or even the mass market due to their low cost, and their flexibility and tracking quality are continuously improving. We here present a new portable low-cost head-mounted eye-tracking system based on the open-source ITU Gaze Tracker software. The setup consists of a pair of self-built tracking glasses with attached cameras for eye and scene recording. The software was significantly extended and functionality was added for calibration in space, scene recording, synchronization for eye and scene videos, and offline tracking. Results of indoor and outdoor evaluations show that our system provides a useful tool for low-cost portable eye tracking; the software is publicly available.

Eye tracking has become cheaper and more robust over the last years. Soon it will be feasible to deploy eye tracking in the mass market. One application area in which an average consumer might benefit from eye tracking is in computer games, where gaze direction can add another dimension of input. Progress in this direction will also be of high relevance to disabled users who lack the dexterity to control the input modalities traditionally used in computer games. Not only could gaming with gaze be enjoyable in itself, but the virtual world of multi-player games might also be one arena where disabled users could meet non-disableds on an equal footing. However, for a satisfactory gaming experience, it does not suffice to simply replace the mouse with a gaze cursor; usually, changes to the game play will also have to be made. In this paper, we will present an open-source game that we adapted so that it can be controlled by either a mouse or by gaze direction. We will show results from a small tournament that indicate that gaze is an equal if not superior input modality for this game.