Vision: Sensory and Perceptual Processing

Light and shadow

Brightly lit objects appear closer, objects in shadows appear farther away

Cornea

Bump in front of the eye

Optic nerve

Carries visual information from the eye to the brain

Atmospheric perspective

Dust, smog, and water vapor make far objects look hazy

Ciliary muscles

Responsible for accommodation, changing the shape of the lens

Visual association cortex

Organizes simple visual sensations, interprets and adds meaning

Linear perspective

Parallel lines appear to converge at a distance

Shape constancy

Perceiving an object as retaining its shape despite changes in viewing angle

Size constancy

Perceiving an object as retaining its size despite changes in distance

Brightness and color constancy

Perceiving an object as retaining the same brightness/color despite changes in lighting

Depth perception

Perceiving depth in visual images

Motion perception

Perceiving movement of objects

Perceptual constancy

Perceiving objects as remaining the same despite changes in the retinal image

Trichromatic theory

Perception of color is based on the response of three types of cones

Cones

Photoreceptors responsible for daytime vision, low sensitivity, high acuity, and color

Rods

Photoreceptors responsible for night vision, high sensitivity, low acuity, and no color

lens

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

Retinal disparity

Binocular cue for depth perception, difference in retinal images of each eye

Convergence

Binocular cue for depth perception, extraocular muscles move eyes to focus

Interposition

Objects that block our view of other objects are closer

Fovea

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

Afterimage

A visual image that persists after a stimulus is removed.

Perceptual adaptation

Ability to adjust to changed sensory input, including an artificially displaced or inverted visual field

Blind spot

Area where the optic nerve leaves the eye, no photoreceptors

Texture gradient

Areas with sharp, detailed texture are interpreted as closer

Cataracts

Clouding of the lens, causing blurry vision

Opponent-process theory

Colors are represented in the visual system as opponent colors

Binocular cues

Cues for depth perception that require both eyes

Monocular cues

Cues for depth perception that require signals from one eye

Figure-ground

Distinguishing between a figure and a background

Visible light

Electromagnetic radiation with wavelengths of ~400-700 nm

Nearsightedness

Eyeball too long, distant images focus in front of retina

Continuity

Favoring smooth or continuous paths when interpreting a series of points or lines

Closure

Filling in missing parts of a figure to see it as complete

Lens

Focuses light on the back of the eye

Common fate

Grouping elements together that are moving together

Similarity

Grouping together elements that appear similar

Proximity

Grouping together objects that are physically close to each other

Pupil

Hole through the iris

Phi phenomenon

Illusion of movement created by blinking lights in quick succession

Color blindness

Inability to distinguish two or more shades in the color spectrum

Sensory restriction

Lack of sensory stimulation, leading to abnormal sensory and perceptual development

Relative size

Larger objects appear closer if we expect them to be the same size

Retina

Light sensitive layer of the eye; contains rods and cones

Primary visual cortex

Receives visual information from the optic nerve, processes basic visual features

Wavelength

Refers to the frequency of a light wave

Restored vision

Regaining vision after a period of sensory restriction

Amplitude

The height of a light wave, known as brightness

Monochromatic color blindness

Total color blindness, world appears in shades of black and white

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

feature detectors

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

Visual Information Processing

optic nerves connect to the thalamus in the middle of the brain, and the thalamus connects to the visual cortex

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

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

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

accommodation

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

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.