Chapter 5: Sensation

sensation

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

perception

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

bottom-up processing

analysis that begins with the sense 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.

psychophysics

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

absolute threshold

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

signal detection theory

a theory predicting how and when we detect the presence of a faint stimulus ("signal") amid background stimulation ("noise"). Assumes that there is no single absolute threshold and that detection depends partly on a person`s experience, expectations, moti

subliminal

below one`s absolute threshold for conscious awareness

difference threshold

the minimum difference between two stimuli required for detection 50 percent of the time; experienced as a just noticeable difference. (Also called just noticeable difference or jnd).

Weber`s law

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

sensory adaption

diminished sensitivity as a consequence of constant stimulation

transduction

conversion of one form of energy into another. In sensation, the transforming of stimulus energies into neural impulses.

wavelength

the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission.

hue

the dimension of color that is determined by the wavelengths 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 a wave`s amplitude.

pupil

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

iris

a ring 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.

accommodation

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

retina

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

acuity

the sharpness of vision.

nearsightedness

a condition in which nearby objects are seen more clearly than distant objects because distant objects focus in front of the retina

farsightedness

a condition in which faraway objects are seen more clearly the near objects because the image of near objects is focused behind the retina.

rods

retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don`t respond.

cones

receptor cells that are concentrated near the center of the retina and that function in daylight or in well - lit conditions; 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.

feature detector

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

parallel processing

the processing of several aspects of a problem simultaneously; the brain`s natural mode of information processing for many functions, including vision. Contrasts with the step-by-step processing of most computers and of conscious problem solving.

Young-Helmholtz trichromatic theory

(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 when stimulated in combination 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.

color constancy

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

audition

the sense of hearing.

frequency

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

pitch

a tone`s highness or lowness; depends on frequency.

middle ear

the chamber between the eardrum and cochlea containing three tiny bones (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrum or the cochlea`s oval window.

inner ear

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

cochlea

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

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.

conduction hearing loss

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

sensorineural hearing loss

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

gate-control theory

the theory that the spinal cord contains 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 travelling up small nerve fibers and is closed by activity in large fibers o

sensory interaction

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

kinesthesis

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.