Sensation and Perception

bottom-up processing

bottom-up processing

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

top-down processing

Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.

transduction

The process of converting one form of energy into another, such as transforming stimulus energies into neural impulses.

psychophysics

The study of the relationship between physical characteristics of stimuli and our psychological experience of them.

absolute threshold

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

signal detection theory

A theory predicting how and when we detect the presence of a faint stimulus amid background stimulation.

subliminal

Below one's absolute threshold for conscious awareness.

priming

The activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response.

difference threshold

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

Weber's law

The principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage.

sensory adaptation

Diminished sensitivity as a consequence of constant stimulation.

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.

intensity

The amount of energy in a light or sound wave, which we perceive as brightness or loudness.

cornea

The eye's clear, protective outer layer.

pupil

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

iris

The colored part of the eye that controls the size of the pupil.

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.

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; 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.

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 color receptors—one most sensitive to red, one to green, one to blue—which can produce the perception of any color.

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

The processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions.

audition

The sense or act of hearing.

frequency

The number of complete wavelengths that pass a point in a given time.

pitch

A tone's experienced highness or lowness; depends on frequency.

middle ear

The chamber between the eardrum and cochlea containing three tiny bones that concentrate the vibrations of the eardrum on the cochlea's oval window.

cochlea [KOHK-lee-uh]

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

inner ear

The innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs.

sensorineural hearing loss

Hearing loss caused by damage to the cochlea's receptor cells or to the auditory nerves.

conduction hearing loss

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

cochlear implant

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

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 the frequency of a tone, thus enabling us to sense its pitch.

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.

gustation

The sense of taste.

olfaction

The sense of smell.

kinesthesis [kin-ehs-THEE-sis]

The system for sensing the position and movement of individual body parts.

vestibular sense

The sense of body movement and position, including the sense of balance.

sensory interaction

The principle that one sense may influence another, as when the smell of food influences its taste.