Module 17: Vision Flashcards
Transduction
conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret.
Wavelength
the distance from the peak of one light wave or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short gamma waves to the long pulses of radio transmission.
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.
Intensity
the amount of energy in a light wave or sound wave, which influences what we perceive as brightness or loudness. Intensity is determined by the wave’s amplitude (height).
Iris
the colored portion of the eye that is a muscle that constrict or expands (dilates) the size of the pupil
Pupil
the adjustable opening in the center of the eye through which light passes
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.
Accommodation
the process by which the eye’s lens changes shape to focus near or far objects on the retina.
Rods
retinal receptors that detect black, white, and gray, and are sensitive to movement; necessary for peripheral and twilight vision, when cones don’t respond.
Cones
retinal receptors that are concentrated near the center of the retina and that function in daylight or in well- lit conditions. Cones detect fine detail and give rise to color sensations.
Optic Nerve
the nerve that carries neural impulses from the eye to the brain.
Blind Spot
the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there.
Fovea
the central focal point in the retina, around which the eye’s cones cluster.
Young-Helmholtz trichromatic (three-color) theory
the theory that the retina contains three different types of 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.
Opponent-process Theory
the theory that opposing retinal processes (red-green, blue-yellow, 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.
Feature Detectors
nerve cells in the brain’s visual cortex that respond to specific features of the stimulus, such as shape, angle, or movement.
Parallel Processing
processing many aspects of a stimulus or problem at once.
Gestalt
an organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes.
Figure-Ground
the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).
Grouping
the perceptual tendency to organize stimuli into coherent groups.
Proximity
the tendency to group nearby things together
Continuity
the tendency to perceive smooth, continuous patterns, rather than discontinuous ones
Closure
the tendency to fill in gaps to create a composite, whole object.
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.
Visual Cliff
a laboratory device for testing depth perception in infants and young animals.
Binocular Cue
a depth cue, such as retinal disparity, that depends on the use of two eyes.
Retinal Disparity
a binocular cue for perceiving depth. By comparing retinal images from the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object.
Monocular Cue
a depth cue, such as interposition or linear perspective, available to either eye alone.
Phi Phenomenon
an illusion of movement created when two or more adjacent lights blink on and off in quick succession.
Perceptual Constancy
perceiving objects as unchanging (having consistent color, brightness, shape, and size) even as illumination and retinal images change.
Perceptual Adaptation
the ability to adjust to changed sensory input, including an artificially displaced or even inverted visual field.
