Kinetic Depth Effect and Optic Flow 1. 3D Shape from Fourier Motion
Abstract
Fifty-three different shapes were defined by sequences of 2 D views (frames) of dots on a rotating 3D surface. (1) Subjects' accuracy of shape identifications dropped from over 90% to less than 10% when either the polarity of the stimulus dots was alternated from light-on-gray on successive frames or when neutral gray interframe intervals were interposed. Both manipulations interfere with motion extraction by spatio-temporal (Fourier) and gradient first-order detectors. Second-order (non-Fourier) detectors that use full-wave rectification are unaffected by alternating-polarity but disrupted by interposed gray-frames. (2) To equate the accuracy of 2AFC planar direction-of-motion discrimination in standard and polarity-alternated stimuli, standard contrast was reduced. 3D discrimination survived contrast reduction is standard stimuli whereas it failed completely with polarity-alternation even at full contrast. (3) When individual dots were permitted to remain in the image sequence for only two frames, performance showed little loss compared to standard displays where individual dots had an expected lifetime of 20 frames, showing that 3D shape identification does not require continuity of stimulus tokens. (4) Performance in all discrimination tasks is predicted (up to a monotone transformation) by considering the quality of first-order information (as given by a simple computation on Fourier power) and the number of locations at which motion information is required.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1987
- Accession Number
- ADA211260
Entities
People
- Barbara A. Dosher
- George Sperling
- Michael S. Landy
Organizations
- New York University