Abstract
Our research aims to find out how deep a visual field is operated for integration of orientations as an ensemble. Ensemble perception is a process that the visual system produces summary statistical representations from any feature. Here we focus on the feature of orientations that is one of the most primary visual characteristics involved in the configuration of objects. The current research investigates integration process of grating orientations in a virtual three-dimensional space using a stereoscope, which could give us a clue to the depth affecting on convergence of the orientations under the size constancy situation. Gratings were defined with 0.5 cycles per degree on the standard picture plane (the physical screen) and a radius of the presentation area was fixed with five degrees of visual angle, irrespective of the depth, but they had apparently never overlapped one another. Eight gratings were randomly presented from the standard picture plane to 100 cm maximum depth and these gratings randomly oriented varying 0.5 degrees to 32 degrees from the average of each trial. After 100 ms presentation of the set, participants indicated to which side it tilted compared to the vertical with two-alternative forced choice. Our results showed that sensitivity to the orientation variance increased in proportion to the depth increase despite the size constancy, suggesting that employed total space had influenced on averaging performances about orientations. For ensemble perception, human visual system does not always integrate all orientation information with the same sensitivity regardless of depth.