Visual processing finds colors, features, parts, wholes, spatial relations, and motions {vision, physiology}. Brain first extracts elementary perceptual units, contiguous lines, and non-accidental properties.
properties: sizes
Observers do not know actual object sizes but only judge relative sizes.
properties: reaction speed
Reaction to visual perception takes 450 milliseconds [Bachmann, 2000] [Broca and Sulzer, 1902] [Efron, 1967] [Efron, 1970] [Efron, 1973] [Taylor and McCloskey, 1990] [Thorpe et al., 1996] [VanRullen and Thorpe, 2001].
properties: timing
Location perception is before color perception. Color perception is before orientation perception. Color perception is 80 ms before motion perception. If people must choose, they associate current color with motion 100 ms before. Brain associates two colors or motions before associating color and motion.
processes: change perception
Brain does not maintain scene between separate images. Perceptual cortex changes only if brain detects change. Perceiving changes requires high-level processing.
processes: contrast
Retina neurons code for contrast, not brightness. Retina compares point brightness with average brightness. Retinal-nerve signal strength automatically adjusts to same value, whatever scene average brightness.
processes: orientation response
High-contrast feature or object movements cause eye to turn toward object direction {orientation response, vision}.
processes: voluntary eye movements
Posterior parietal and pre-motor cortex plan and command voluntary eye movements [Bridgeman et al., 1979] [Bridgeman et al., 1981] [Goodale et al., 1986]. Stimulating superior-colliculus neurons can cause angle-specific eye rotation. Stimulating frontal-eye-field or other superior-colliculus neurons makes eyes move to specific locations, no matter from where eye started.
information
Most visual information comes from receptors near boundaries, which have large brightness or color contrasts. For dark-adapted eye, absorbed photons supply one information bit. At higher luminance, 10,000 photons make one bit.
Consciousness>Consciousness>Sense>Vision>Physiology
1-Consciousness-Sense-Vision-Physiology
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Date Modified: 2022.0224