Purpose: To understand how observers know where they are going on the basis of visual information while moving through cluttered environments and exercising natural gaze patterns. Our pre"ious research has suggested that people use depth-registered, local information (t ie displacement of particular objects as they are laid out in the visual field), rather than depthless, global information (the pooled motion of all objects in the visual field irrespective of depth) to make heading judgments. Here we explored ot servers' ability to make heading judgments-both nominal and absolute-tram displays with only a few objects. Methods: Stimulus trials mimicked loccmotion across a plane while looking at a stationary object (a tree) and approach! ig it at angles between 1 and 8 deg. Various sources of local information con ;erning the other trees (displacement of the nearest object in the field of view, inward displacements, and outward deceleration) were manipulated. Observers responded indicating their absolute heading by manipulating a computer-con trolled mouse. Results: Nominal judgments of heading direction (those to the correct side of the fixation tree) were nearly adequate w len compared to task requirements of everyday gait. Thus, performance in minimal environments is only slightly worse than in cluttered ones. Results weie also consistent with the idea that several sources of local information predict observer performance. Absolute judgments of heading were uncorrelated with the number of trees present, but instead were correlated with the number of sources of information present. Conclusions: When fixating an object while locomoting, the ground plane of the visual world rotates around that objet t. The direction of this rotation specifies the direction of heading (clockwise mear s heading is to the right of gaze direction). The three local sources invest gated here are emblems of this rotation.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience