| Term | Definition |
|---|
| 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 |
| 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") |
| subliminal | below one's absolute threshold for conscious awareness |
| priming | the activiation, 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 percent of the time (also called just noticeable difference or jnd) |
| 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) |
| sensory adaptation | diminished sensitivity as a consequence of constant stimulation |
| transduction | 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 |
| hue | the dimension of color that is determiend 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 |
| 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 |
| 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 the 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 than 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 | retinal receptors cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions; they 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 |
| parallel processing | the processing of several aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision |
| 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 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 |
| color constancy | perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object |
| 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 (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrum on the cochlea's oval window |
| cochlea | 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 |
| 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 |
| cochlear implant | a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea |
| 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 |
| olfaction | the sense or act of smelling |
| 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 |
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