Sensation and Perception

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 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.

selective attention

the focusing of conscious awareness on a particular stimulus.

inattentional blindness

failing to see visible objects when our attention is directed elsewhere.

change blindness

failing to notice changes in the environment.

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 there is no single absolute threshold and that detection depends partly on a person's experience, expectations, motivation, and alertness.

subliminal message

anything below our absolute threshold

difference threshold

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

Weber's law

the principle that, to be perceived as different, two 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. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brains can interpret.

wavelength

the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic versions of this 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 wavelength 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 the wave's amplitude.

cornea

transparent front that protect eye and bend light to provide focus

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.

fovea

central point in the retina; cones cluster here

accomodation

Sensation - 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, when cones don't respond.

cones

retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. These 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 and no receptor cells are located there.

fovea

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

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, including vision. Contrasts with the step-by-step (serial) processing of most computers and of conscious problem solving.

Trichromatic 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. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green.

audition

the sense or act of hearing.

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.

Pinna

collect sound wave and funnels them into the auditory canal

auditory canal

connect outer ear to middle ear

middle ear

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

cochlea

snail shape; convert vibration into neural impulses

hair cells

inside of the cochlea that activate in response to the vibration from the middle ear

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 something going wrong with the vibration through the ear

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 and movement of individual body parts.

vestibular sense

the sense of body movement and 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 and is closed by activity in larger fibers or by information coming from the brain.

sensory interaction

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

Gestalt Psychology

emphasized our tendency to integrate pieces of information into meaningful wholes

figure-ground

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

grouping

the perceptual tendency to organize stimuli into coherent groups.

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

our eyes each see a slightly different image; the image disparity will be greater for closer objects

monocular cues

depth cues, such as interposition and linear perspective, available to either eye alone.

phi phenomenon

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

perceptual constancy

perceiving objects as unchanging (having consistent shapes, size, lightness, and color) even as illumination and retinal images change.

perceptual adaptation

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

perceptual set

previous experience influencing your mental predisposition to perceive one thing and not another

extrasensory perception (ESP)

the controversial claim that perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition.

parapsychology

the study of paranormal phenomena, including ESP and psychokinesis.

decibels

unit for sound intensity

Bipolar cells & Ganglion cell

above cones and rods in the redina

thalamus and visual cortex

receive information from the optic nerve

synesthesia

associating one sensory with another sensory

Four skin sensation

pressure, pain, cold, warmth

5 sensation of taste buds

sweat, salty, bitter, sour, umami

smell sense does not pass through…

thalamus in the brain, all other do