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 process, as when we construct perceptions drawing out our experience and expectation.
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 stimuli ("signal") amid background stimulation ("noise"). Assume that there is no single absolute threshold and that focuses more on the processing of briefly stored information. (e.g. what determines a "hit", "miss," "false alarm" or "correct rejection")
Difference threshold
the minimum difference between two stimuli required for detection 50 percent of the time. We experience the difference threshold as a just noticeable difference (also called just noticeable difference or JND.)
Subliminal Sensation
detection of stimuli below absolute threshold
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. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission.
Hue
the dimension of color that is determine by the wavelength of light; what we know as the color names blue, green, and so forth.
Pupil
the adjustable opening in the center of the eye through which light enters.
Iris
a ring of muscle tissue that forms the color portions 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 right in front of the retina.
Farsightedness
the condition in which faraway objects are seen more clearly that 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
receptors cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine details and give rise to color sensation.
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 receptors cells are located there. Creates a gap in our vision that is "filled" by the brain.
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 stimuli, 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. Contrast with the step-by-step (serial) processing of most computers and of conscious problem solving.
Young-Helmholtz Trichromatic theory
the theory that the retina contains three different colors 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; useful for explaining the phenomenon of "after-images"
Color constancy
perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the objects.
Audition
the sense of hearing
Frequency
the number of complete wavelengths that pass a point in a given time.
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, semicircular canals, and vestibular sacs.
Cochlea
a coiled bony, fluid-filled tube in the inner ear through which sound waves trigger nerve 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 its pitch.
Gate-Control theory
the theory that the spinal cord contains neurological "gate" that blocks pain signals or allows them to pass on to the brain. The "gate" is open by the activity of pain signals traveling up small nerve fibers and is closed by activity in larger fibers or by information coming form the brain.
Kinesthesis
the system for sensing the position and movement of individual body parts; enabled by feedback from proprioceptors (which provide info about the movement of muscles, tendons, joints)
Vestibular sense
the sense of body movement and position, including the sense of balance; enabled by feedback from semicircular canals in inner ear
basilar membrane
area within the cochlea where hair cells are located
gestalt
a perceptual whole; derived from German word meaning "form" or "whole"
selective attention
ability to attend to only a limited amount of sensory information at one time
figure-ground
A gestalt perceptual phenomenon; the organization of the visual field into objects that stand out from their surroundings
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
laboratory device for testing depth perception among infants and young animals; its use demonstrated that, among most species, animals have the ability to perceive depth by the time they are mobile
binocular cues
depth cues that require the combined input of both eyes
monocular cues
depth cues that only require input from one eye; often used in 2D art to create illusion of depth
convergence
a binocular cue for perceiving depth; the more the eyes strain to turn inwards to view an object, the closer the object is (note: only a factor at close ranges)
interposition
monocular cue for depth perception; if one object partially blocks our view of another object, we perceive it as closer
relative motion
monocular cue for depth perception; as we move, stationary objects seem to "move" as well. Objects above a fixation point move "with" us, objects below the fixation point move "past" us.
phi phenomenon
an illusion of movement created when two or more adjacent lights blink on and off in rapid succession
stroboscopic movement
the brain's perception of continuous movement in a rapid series of slightly varying images; this is how we perceive motion in film and animation
perceptual constancy
perceiving objects as unchanging (having consistent shapes, size, lightness, and color) even as illumination and retinal images change
perceptual adaptation
the ability to adjust to an altered perceptual reality; in vision, the ability to adjust to an artificially displaced or inverted visual field (as when wearing visual displacement goggles).
perceptual set
mental predisposition to perceive one thing and not another (for example, due to suggestion or expectations based on prior learning)
human factors psychology
Branch of psychology that explores how people & machines interact and how physical environment can be adapted to human behaviors
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
visual capture
the phenomenon that occurs when vision overtakes some other, conflicting sensory input
retinal disparity
a binocular cue for perceiving depth; by comparing images from the two eyeballs, the brain computes distance - the greater the disparity (difference) between the two images, the close the object
Inattentional Blindness
failing to see visible objects when our attention is directed elsewhere
cochlear implant
a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea
Sensorineural Hearing Loss
hearing loss due to failure of the auditory nerve
Conduction Hearing Loss
hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea
Decibels
measure of loudness of sound
Pitch
the property of sound that varies with variation in the frequency of vibration
Intensity
the magnitude of sound (usually in a specified direction)
Priming
the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response
Psychophysics
the branch of psychology concerned with quantitative relations between physical stimuli and their psychological effects