Visual Perception of Elevation
Annual rept. 1 Jan-31 Dec 1991
COLUMBIA UNIV NEW YORK DEPT OF PSYCHOLOGY
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The experiments demonstrate the importance for human observers of the retinal orientation and location of individual straight lines in determining 1 the physical elevation visually perceived as being at eye level VPEL, and 2 the orientation within a frontal plane visually perceived as being vertical VPV. The particular depth plane is unimportant for each discrimination as shown by experiments in which stimuli at the same retinal location from differently pitched and differently rolled planes of different depth influence each discrimination identically. The laws of spatial summation for lines controlling VPEL have been determined and are very different than for other visual discriminations Influences for a parallel line set summate across a negatively accelerated exponential with a 15.10 space constant lines from nonparallel sets make use of a mechanism that takes a weighted average of their individual influences. The time course for light and dark adaptation of VPEL for a 2-line stimulus is similar to that for a normally illuminated and fully structured pitched visual environment. The VPEL discrimination is near- spatiotopic for eye position and head orientation. The analysis of results at 1.5G has not yet been completed. but it appears that a bias with only minimal influence on the slope of the VPEL vs-pitch function results from change of G. Spatial localization, Pitch, Roll, Eye level, Visual localization, VPEL, VPV, Perception, Egocentric spatial localization, Vertical.