Abstract
The bulk of published data on eye movements have been gathered in laboratory settings. One eye of a seated observer is often tracked while s/he views static objects or images constrained to a single depth plane. By contrast, eye movements in natural environments are often made while the observer and/or target are in motion, to objects that vary in both direction and depth. We monitored monocular and binocular eye movements of mobile observers as they performed a number of tasks, from scanning a 3D array of targets while seated in the laboratory, to navigating footpaths in natural, wooded environments. A custom-built wearable eyetracker was used to monitor version and vergence eye movements of observers performing the tasks under a range of conditions. Monocular and binocular eye movements were studied within a 3-dimensional array of calibration points surrounding observers indoors, free viewing outdoor scenes, a visual search task, and while walking indoors and out.
In the free-view task observers were instructed to simply familiarize themselves with a region defined as the hemisphere forward from their fixed viewpoint. In the visual search task, observers searched for a small target within a hemisphere. Free to move their heads and bodies, large gaze changes (> 30 deg) were common. Fixations durations in the search task ranged from 1000 msec fixations while inspecting high-density regions. While it is possible to extract individual version and vergence ‘components’ of gaze shifts between targets in 3D space, the right and left eye movements each exhibit main-sequence saccadic characteristics; the dynamics of each determined by the relative location of the two eyes and the sequence of targets.