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% of the time.
Signal Detection Theory
A theory predicting how and when we detect the presence of a faint stimulus 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 l
Subliminal
Below one's absolute threshold for conscious awareness.
Difference Threshold
The minimum difference between 2 stimuli required for detection 50% of the time. We experience this as a just noticeable difference.
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
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.
Hue
The dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, etc.
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 grey; 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 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; no receptor cells are located there.
Fovea
The central focus 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 several aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision.
Young-Helmholtz Trichromatic Theory
The theory that the retina contains three different color receptors- red, green, and blue- which when stimulated in combination can produce the perception of any color.
Opponent Process Theory
The theory that opposing retinal processes 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 of complete wavelengths that pass a point in a given time.
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 on the cochlea's oval window.
Inner Ear
The innermost part of the ear, containing the cochlea, semicircle canals, and vestibular sacs.
Cochlea
A coiled, bony, fluid-filled tube in thee inner ear through which sound waves trigger neural 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 a 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 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
Sensory Interaction
The principle that one sense may influence another, as when the smell of food influences its taste.
Kinisthesis
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.