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Absolute Threshold

The minimum stimulation needed to detect a particular stimulus 50 percent of the time

Accommodation

(1) The process by which the eye's lens changes shape to focus near or far objects on the retina. (2) Adapting our current understandings to incorporate new information.

Audition

The sense or act of hearing.

Binocular Cues

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

Blind Spot

the point at which the optic nerve leaves the eye, creating a spot where there are no receptor cells, a spot in which is not visible.

Bottom-Up Processing

Analysis that begins with the sensory receptors and works up to the brain's integration of sensory information.

Change Blindness

Failing to notice changes in the environment.

Cochlea

A coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses.

Cochlear Implant

A device for converting sounds into electrical signals and stimulation the auditory nerve through electrodes threaded in the cochlea.

Color Constancy

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

Conduction Hearing Loss

Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea.

Cones

Retinal receptor cells that are concentrated near the center of the retina and that function in well-lit conditions. The cones detect fine detail and give rise to color sensations.

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.

Difference Threshold

The minimum difference between two stimuli required for detection 50 percent of the time.

Extrasensory Perception

The controversial claim that perception can occur apart from sensory input.

Feature Detectors

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

Parallel Processing

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

Young-Helmholtz Trichromatic (three-color) Theory

the theory that the retina contains 3 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 (white-black, red-green) enable color vision. ex: some cells are stimulated by green and inhibited by red, or vice versa

Frequency

the number of complete wavelengths that pass a point in a given time (for example, per second)

Pitch

a tone's experienced highness or lowness; depends on frequency

Middle Ear

the chamber between the eardrum & cochlea containing 3 tiny bones (hammer, anvil & stirrup) that concentrate the vibrations of the eardrum on the cochlea's oval window

Inner Ear

the innermost part of the ear, containing the cochlea, semicircular canals, & vestibular sacs

Place Theory

in hearing, the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated

Frequency Theory

in hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches that frequency of a tone, thus enabling us to sense its pitch

Sensorineural Hearing Loss

hearing loss caused by damage to the cochlea's receptor cells or to the auditory nerves; also called nerve deafness

Kinesthesis

the system for sensing the position & movement of individual body parts

Vestibular Sense

the sense of body movement & position, including the sense of balance

Gate-Control Theory

the theory that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass on to the brain. The "gate" is opened by the activity of pain signals traveling up small nerve fibers & is closed by activity in larger fibers or by information coming from the brain

Sensory Interaction

the principle that one sense may influence another

Gestalt

an organized whole

Figure-Ground

the organization of the visual field into objects (figures) that stand out from their surroundings (ground)

Grouping

the perceptual tendency to organize stimuli into coherent groups

Visual Cliff

a laboratory device for testing depth perception in infants & young animals

Retinal Disparity

a binocular cue for perceiving depth: by comparing images from the retinas in the 2 eyes, the brain computes distance; the greater the disparity, the closer the object

Monocular Cues

depth cues (such as interposition & linear perspective) available to either eye alone

Phi Phenomenon

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

Perceptual Constancy

perceiving objects as unchanging, even as illumination & retinal images change

Perceptual Adaptation

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

Perceptual Set

a mental predisposition to perceive one thing & not another

Parapsychology

the study of paranormal phenomena, including ESP ^ & psychokinesis

Sensation

the process by which our sensory receptors & nervous system receive & represent stimulus energies from our environment

Perception

the process of organizing & interpreting sensory information, enabling us to recognize meaningful objects & events

Top-Down Processing

information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience & expectations

Selective Attention

the focusing of conscious awareness on a particular stimulus

Inattentional Blindness

failing to see visible objects when our attention is directed elsewhere

Psychophysics

the study of relationships between the physical characteristics of stimuli, such as their intensity, & our psychological experience of them

Signal Detection Theory

a theory predicting how & when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no single absolute threshold & that detection depends partly on a persons experience, expectation, motivation & alertness

Subliminal

below one's absolute threshold for conscious awareness

Priming

the activation, often unconsciously, of certain assosciations, thus predisposing one's perception, memory or response

Weber's Law

the principle that, to be perceived as different, 2 stimuli must differ by a constant percentage (rather than a constant amount)

Sensory Adaptation

diminished sensitivity as a consequence of constant stimulation

Transduction

conversion of one form of energy into another. ex. sensation: stimulus energies to neural impulses our brains can interpret

Wavelength

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

Hue

the dimension of color that is determined by the wavelength of light (color names like blue)

Intensity

the amount of energy in a light or sound wave as determined by the waves amplitude

Pupil

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

Iris

the ring of muscle tissue that forms the colored portion of the eye around the pupil & controls the size of the pupil opening

Lens

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

Retina

the light-sensitive inner surface of the eye, containing the receptor rods & cones plus layers of neurons that begin the processing of visual information

Rods

retinal receptors that detect black, white, gray; necessary for peripheral & twilight vision, when cones don't respond

Optic nerve

the nerve that carries neural impulses from the eye to the brain

Fovea

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

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