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Sensation |
Absolute Threshold
The minimum stimulation needed to detect a particular stimulus 50 percent of the time.
Accommodation
The process by which the eye’s lens changes shape to focus the image of near objects on the retina.
Acuity
The sharpness of vision.
Audition The sense of hearing. Blind Spot
The point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there.
Bottom-up Processing
Analysis that begins with the sense receptors and works up to the brain’s integration of sensory information.
Cochlea A coiled, bony, fluid filled tube in the inner ear through which sound waves trigger nerve impulses. Cocktail Party Effect
The ability to attend selectively to only one voice among many.
Color Constancy
Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object.
Conduction Hearing Loss
Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea.
Cones
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.
Difference Threshold The minimum difference that a person can detect between two stimuli. We experience the difference threshold as a just noticeable difference. (Also called the just noticeable difference). Farsightedness A condition in which faraway objects are seen more clearly than nearby objects because the image of near objects is focused behind the retina. Feature Detectors Nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement. Fovea
The central focal point in the retina, around which the eye’s cones cluster.
Frequency The number of complete wavelengths that pass a point in a given time. 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 Theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows the 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 by information coming from the brain. 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.
Inner Ear The innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs. 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.
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.
Kinesthesis
The system for sensing the positions and movement of individual body parts.
Lens The transparent structure behind the pupil that changes shape to focus images on the retina. 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.
Nearsightedness
A condition in which nearby objects are seen more clearly than distant objects because the lens focuses the image of distant objects in front of the retina.
Opponent-Process Theory The theory that opposing retinal processes (red-green, yellow-blue, black-white) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green. Optic Nerve
The nerve that carries neural impulses from the eye to the brain.
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 (serial) processing of most computers and of conscious problem solving. Perception
The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.
Pitch A tone’s highness or lowness; depends on frequency. Place Theory
In hearing, the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated.
Psychophysics
The study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them.
Pupil
The adjustable opening in the center of the eye through which light enters.
Retina
The light- sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that being 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.
Selective Attention
The focusing of conscious awareness on a particular stimulus, as in the cocktail party effect.
Sensation
The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.
Sensorineural Hearing Loss Hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves; also called nerve deafness. Sensory Adaptation
Diminished sensitivity as a consequence of constant stimulation.
Sensory Interaction
The principle that one sense may influence another, as when the smell of food influences its taste.
Signal Detection Theory
Predicts 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, motivation, and level of fatigue.
Subliminal
Below one’s absolute threshold for conscious awareness.
Top-down Processing
Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.
Transduction
Conversion of one form of energy into another. In sensation, the transforming of stimulus energies into neural impulses.
Vestibular Sense
The sense of body movement and position, including the sense of balance.
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.
Weber’s Law
The principle that, to perceive their difference, two stimuli must differ by a constant minimum percentage (rather than a constant amount).
Young- Hemholtz Trichromatic Theory
The theory that the retina contains three different color receptors- one most sensitive to red, one to green, and one to blue- which when stimulated in combination can produce the perception of any color.