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14 Cards in this Set
- Front
- Back
Objective
Distinguish between rods and cones. |
Rods are types of visual receptors (120 million) that are mostly found in the periphery of the human retina.
Most sensitive to low levels of light Provide poor acuity Cones are receptors (6 million) that are more prevalent in the central retina (fovea) Sensitive to bright light Provide excellent acuity Essential for color vision |
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Objective
Distinguish the three major theories of color vision. |
1. Young-Helmholtz Theory
2. Opponent-Process Theory 3. Retinex Theory |
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Objective
Explain how color blindness occurs. |
For genetic reasons, some people lack one or two types of cones. Some have all three kinds, but one kind has abnormal properties.
In the most common form of color vision deficiency, people have distinguishing red from green because their long and medium wavelengt cones have the same photopigment instead of different ones. The gene causing this deficiency is on the X chromosome. |
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rods
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Receptors that are abundant in the periphery of the human retina
Respond to faint light Not useful in bright daylight because bright light bleaches them |
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cones
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Receptors that are most abundant in and around the fovea
Less active in dim light More useful in bright light Essential for color vision |
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photopigment
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Chemicals that release energy when struck by light
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Trichromatic (Young-Helmholtz) Theory
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Theory that states that we perceive color through the relative rates of response by three kinds of cones, each kind normally sensitive to a different set of wavelengths
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psychophysical observations
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Reports by observers concerning their perceptions of various stimuli
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visual field
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Part of the world that you see
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negative color afterimage
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A replacement of the red you have been starting at with green, green with red, yellow and blue with each other, and black and white with each other
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Opponent-Process Theory
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We perceive color in terms of paired opposites
Red vs. Green Yellow vs. Blue White vs. Black |
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color constancy
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Ability to recognize the color of an object despite changes in lighting
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retinex theory
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The cortex compares information from various parts of the retina to determine the brightness and color for each area
Example: If the cortex notes a constant amount of green throughout a scene, it subtracts some green from each object to determine its true color |
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color vision deficiency
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An impairment in perceiving color differences compared to other people
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