Parallel Computation of Vernier Offsets, Curvature, and Chevrons in Humans
Abstract
A vernier offset is detected at once among straight lines, and reaction times are almost independent of the number of simultaneously presented stimuli (distractors), even if absolute orientation cues are masked by varied orientation of the verniers. This result implies that the human visual system processes vernier offsets in parallel. Reaction times for identifying one straight target among offset verniers, on the other hand, increase with the number of stimuli. The same is true for the identification of a vernier offset to one side among verniers offset to the opposite side, if absolute orientation cues are masked. These tasks require serial or semi-parallel processing. Chevrons and curved targets show the same pattern of results. Even deviations below a photoreceptor diameter can be detected at once. The visual system thus attains positional accuracy below the photoreceptor diameter simultaneously at different positions. I conclude that deviation from straightness, or change of orientation, is detected in parallel over the visual field. Discontinuities or gradients in orientation may represent an elementary feature of Parallel processing, Human psychophysics, Hyperacuity, Early vision.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1989
- Accession Number
- ADA282416
Entities
People
- Manfred Fahle
Organizations
- Massachusetts Institute of Technology