the process by which the eye's lens changes shape to focus near or far objects on the retina.
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binocular cues
depth cues, such as retinal disparity, that depend on the use of two eyes.
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blind spot
the point at which the optic nerve leaves the eye, creating a "blind" spot because no receptor cells are located there.
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color constancy
perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object.
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cones
retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations.
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depth perception
the ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance.
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feature detectors
nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement.
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figure-ground
the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).
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fovea
the central focal point in the retina, around which the eye's cones cluster.
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gestalt
an organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes.
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grouping
the perceptual tendency to organize stimuli into coherent groups.
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hue
the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth.
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intensity
the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave's amplitude.
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iris
a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening.
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lens
the transparent structure behind the pupil that changes shape to help focus images on the retina.
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monocular cues
depth cues, such as interposition and linear perspective, available to either eye alone.
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opponent-process theory
the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green.
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optic nerve
the nerve that carries neural impulses from the eye to the brain.
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parallel processing
the processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision. Contrasts with the step-by-step (serial) processing of most computers and of conscious problem solving.
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perceptual adaptation
in vision, the ability to adjust to an artificially displaced or even inverted visual field.
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perceptual constancy
perceiving objects as unchanging (having consistent shapes, size, brightness, and color) even as illumination and retinal images change.
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phi phenomenon
an illusion of movement created when two or more adjacent lights blink on and off in quick succession.
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pupil
the adjustable opening in the center of the eye through which light enters.
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retina
the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information.
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retinal disparity
a binocular cue for perceiving depth: By comparing images from the retinas in the two eyes, the brain computes distance- the greater the disparity (difference) between the two images, the closer the object.
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rods
retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond.
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visual cliff
a laboratory device for testing depth perception in infants and young animals.
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wavelength
the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission.
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Young-Helmholtz trichromatic (three-color) theory
the theory that the retina contains three different color receptors-one most sensitive to red, one to green, one to blue-which, when stimulated in combination, can produce the perception of any color.
Studied by 2 people
