Module 18-19

Gestalt

an organized whole that is perceived as more than the sum of its parts.

figure-ground

the organization of the visual field into objects that stand out from their surroundings

Proximity

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

Continuity

we perceive smooth, continuous patterns rather than discontinuous ones

Closure

we fill in gaps to create a complete, 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 cues

depth cues, such as retinal disparity, 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

relative height

we perceive objects higher in our field of vision as farther away

relative size

a monocular cue for perceiving depth; the smaller retinal image is farther away

Interposition

if one object partially blocks our view of another, we perceive it as closer

linear perspective

A monocular cue for perceiving depth; the more parallel lines converge, the greater their perceived distance.

phi phenomenon

an illusion of movement created when two or more adjacent lights blink on and off in quick succession

stroboscopic movement

a type of apparent movement based on the rapid succession of still images, as in motion pictures

perceptual constancy

perceiving objects as unchanging even as illumination and retinal images change

color constancy

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

Wavelength

the distance from the peak of one light or sound wave to the peak of the next.

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 transparent outer covering 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

Rods

retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision

Cones

retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions and give rise to color sensations.

optic nerve

carries neural impulses from the eye to the brain

blind spot

the point at which the optic nerve leaves the eye and no receptor cells are located there.

Fovea

the central focal point in the retina, around which the eye's cones cluster

trichromatic theory

theory of color vision that proposes three types of cones: red, blue, and green

opponent-process theory

the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision.

feature detectors

nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement

parallel processing

processing many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision

hue

a particular shade of a given color

accommodation

the process by which the eye's lens changes shape to focus near or far objects on the retina