Unit 4 Vocab - Mod 18 & 19

Wavelength

Wavelength

The distance between two corresponding parts of a wave.

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 or sound wave, which we perceive as brightness or loudness, as determined by the wave's amplitude.

Cornea

The clear tissue that covers the front of the eye.

Pupil

The adjustable opening in the center of the eye through which light enters.

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.

Lens

The transparent structure behind the pupil that changes shape to help focus images on the retina.

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.

Accomodation

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; necessary for peripheral and twilight vision, when cones don't respond.

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.

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 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.

Opponent-Process Theory

The theory that opposing retinal processes enable color vision.

Parallel Proccessing

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.

Blindsight

A condition in which a person can respond to a visual stimulus without consciously experiencing it.

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).

Proximity

We group nearby figures together. We see not six separate lines, but three sets of two lines.

Continuity

We perceive smooth, continuous patterns rather than discontinuous ones.

Closure

The tendency to complete figures that are incomplete.

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.

Visual Cliff Experiment

Gibson and Walk. Infants as young as 6 months usually hesitate to crawl past the apparent edge of a visual cliff, which suggests that they are able to perceive depth.

Binocular Cues

Depth cues, such as retinal disparity and convergence, that depend on the use of two eyes.

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.

Monocular Cues

Depth cues, such as interposition and 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 even as illumination and retinal images change.

Interposition

Monocular visual cue in which two objects are in the same line of vision and one partially conceals the other, indicating that the first object concealed is further away.

Color Constancy

Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object.

Perceptual Adaptation

In vision, the ability to adjust to an artificially displaced or even inverted visual field.

Shape Constancy

The tendency to interpret the shape of an object as being constant, even when its shape changes on the retina.

Relative Motion

As we move, objects that are actually stable may appear to move.