Laboratory based research has shown that the use of stereoscopic displays and observer-produced motion parallax in telepresence systems can each improve operators' performance beyond that achieved using conventional 2-D displays. In applied contexts such as minimal access surgery (MAS) tasks are more complex and a range of sources of depth information is available. We therefore decided to examine the benefits of stereoscopic displays and observer-produced motion parallax under more realistic conditions. The 'pick and place' task was taken from surgical performance studies. It involved picking up small irregular spheres from one place and dropping them through apertures in another. The task was performed under seven different viewing conditions: (1) baseline (monocular), (2) biocular, (3) stereoscopic, (4) free motion parallax, (5) instructed motion parallax, (6) augmented motion parallax and (7) stereo and motion parallax. Each subject did a baseline condition (monocular viewing) followed by one of the seven experimental conditions, followed by a final block of the baseline condition (n = 7 conditions x 10 subjects). Only stereoscopic viewing (conditions 3 and 7) leads to better performance. The provision of motion parallax adds nothing to performance. It may even reduce the effectiveness of stereoscopic viewing. The evidence converges on the fact that binocular viewing confers a considerable performance advantage, while providing motion parallax information, to novice operators at least, is not beneficial.
Many telepresence systems have the capacity to 'slave' camera orientation to the observer's head movements. This results in mimicking the changes in the visual field that would be produced by the observer's head movements. In theory this should result in enhanced depth perception, but in practice the effect often appears to be weak. We report a series of experiments that explore the benefit of providing observer generated motion information (OGMI) across a range of perceptual and perceptual motor tasks. Experiment 1 found that when OGMI was the sole source of depth information observers were able to exploit it in a simple depth judgement task. However, Experiment 2 found that it was unimportant that the motion information was generated by the observer; rather relative motion within the image was sufficient. Experiment 3 used a simple depth adjustment task and found that if subjects first did the task without OGMI they did not benefit by its subsequent availability, suggesting that use of OGMI is not automatic. Experiments 4 and 5 used tracking tasks and found no gain from making OGMI available relative to static viewing of the video image. Overall the results confirm that OGMI confers only weak gains on the accuracy of spatial tasks and that the magnitude of the gains are task dependent.