Sensation and the Senses

sensory adaptation

tendency of sensory receptor cells to become less responsive to a stimulus that is unchanging

Habituation

tendency of the brain to stop attending to constant, unchanging information

absolute threshold

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

difference threshold

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

just noticeable difference

the minimal change in a stimulus that can just barely be detected

Weber's Law

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

subliminal

below one's absolute threshold for conscious awareness

dual processing

the principle that information is often simultaneously processed on separate conscious and unconscious tracks

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.

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

Psychophysics

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

selective attention

the focusing of conscious awareness on a particular stimulus

inattentional blindness

failure to detect stimuli that are in plain sight when our attention is focused elsewhere

cocktail party effect

Ability to concentrate on one voice amongst a crowd

change blindness

failing to notice changes in the environment

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.

Priming

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

Cornea

the transparent layer forming the front of the eye.

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

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. The cones detect fine detail and give rise to color sensations.

Fovea

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

feature detectors

neurons in the brain's visual cortex that respond to specific features of the stimulus, such as shape, angle, or movement

ganglion cells

In the retina, the specialized neurons that connect to the bipolar cells; the bundled axons of the ganglion cells form the optic nerve.

bipolar cells

eye neurons that receive information from the retinal cells and distribute information to the ganglion cells

visual cortex

The visual processing areas of cortex in the occipital lobe

Thalamus

the brain's sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex

optic chiasm

the point in the brain where the visual field information from each eye "crosses over" to the appropriate side of the brain for processing

trichromatic theory

Visual theory, stated by Young and Helmholtz that all colors can be made by mixing the three basic colors: red, green, and blue; a.k.a the Young-Helmholtz theory.

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

Afterimage

A visual image that persists after a stimulus is removed (opponent process theory)

blind spot

the point at which the optic nerve leaves the eye, creating a "blind" spot because no receptor cells are located there

Photoreceptors

rods and cones

audition

the sense or act of hearing

Ossicles

three tiny bones in the middle ear

cochlea

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

semicircular canals

three canals within the inner ear that contain specialized receptor cells that generate nerve impulses with body movement

eardrum

a thin membrane that marks the beginning of the middle ear; sound waves cause it to vibrate

basilar membrane

A structure that runs the length of the cochlea in the inner ear and holds the auditory receptors, called hair cells.

Conductive hearing loss

hearing impairment caused by interference with sound or vibratory energy in the external canal, middle ear, or ossicles

sensorineural hearing loss

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

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

temporal lobe

A region of the cerebral cortex responsible for hearing and language.

olfactory bulb

the brain center for smell, located below the frontal lobes

sensory interaction

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

Gustation

sense of taste

gustatory receptors

chemoreceptors on the tongue that respond to chemicals in food

umami

taste for monosodium glutamate

Supertasters

people with heightened sensitivity to all tastes and mouth sensations

Nociceptors

pain receptors

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.

somatosensory cortex

area at the front of the parietal lobes that registers and processes body touch and movement sensations

parietal lobe

A region of the cerebral cortex whose functions include processing information about touch.

vestibular sense

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

kinesthetic sense

sense of the location of body parts in relation to the ground and each other

Cerebellum

the "little brain" at the rear of the brainstem; functions include coordinating movement output and balance

vestibular sense

semicircular canals