Psych 1000 chapter 5 textbook notes

Visual acuity ability to see fine detail increases

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Visual acuity (ability to see fine detail) increases with image directly on fovea o Blind spot exists at point where ganglion cells exit to form optic nerve
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Transduction - process where characteristics of a stimulus are converted into nerve impulses o Rods and cones accomplish transduction through photopigments o Absorption of light be photopigments increases release of neurotransmitters Brightness Vision and Dark Adaptation o Dark adaptation – the progressive improvement in brightness sensitivity that occurs over time in low illumination Cones adapt completely in 10 minutes Rods continue adapting for 30 minutes, allowing extreme sensitivity to light Color vision o Trichromatic theory – three types of color receptors in retina (blue, green, red) All colors produced by combination of wavelengths between these three colors Flaws in theory: Yellow produced by red and green, yet people with red-green color blindness can see yellow Color afterimage (image in different color appears after stimulus shown for a while then withdrawn) o Opponent-process theory – three color receptors, each responding to two different wavelengths (red-green, blue-yellow, black-white) Explains color afterimage issue o Dual processes in color transduction Modern dual-process theory combines both theories to account for color transduction process Cones contain one of three different photopigments that are sensitive to blue, green, and red Different combinations of intensities will produce different colors Opponent processes occur, but not in cones Ganglion cells respond in opponent-process by altering firing rate o Color-deficient vision Dichromat – color blind to only one system (red-green or yellow-blue) Monochromat – completely colorblind (only sees black-white) Analysis and Reconstruction of Visual Scenes o Feature detectors Optic nerve sends nerve impulses to brain (thalamus, then primary visual cortex) Groups of neurons in the cortex are organized to receive and integrate sensory nerve impulses from specific regions of retina Feature detector cells fire selectively to stimuli that have specific characteristics Certain cells fire when horizontal line present, others when other angles present Parallel processing – different cells analyze stimuli and construct unified image of its properties o Visual association processes Information analyzed and reconstructed in primary visual cortex is routed to other regions known as visual association cortex Audition Frequency – number of sound waves or cycles per second (Hz = one cycle per second) Amplitude – vertical size of the sound waves (decibels – db) Transduction system of ear is made up of bones, membranes, and tubes o Sound waves vibrate eardrum, which vibrates three bones (hammer, anvil, and stirrup)
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  • Spring '09
  • Psychology, Color blindness

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