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.
psychophysics
the study of relationship between the physical characteristic 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 stimuli ("signal") amid background stimulation ("noise"). Assumes 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% of the time; also referred to as just noticeable difference (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.
amplitude
height of a wave; influences brightness in visual perception and volume in audition
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.
rods
Retinal receptors that detect black, white, and gray; 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 in well-lit conditions. They 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; determines perception of hue in light and of pitch in sound
pitch
sound information that depends on frequency (or wavelength) of sound waves
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.
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) middle ear structures that conduct sound waves to the cochlea.
sensorineural hearing loss
hearing loss caused by damage to the cochlea's receptors cells or to the auditory nerves; also called nerve deafness.
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.
kinesthesia
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); also called "proprioception
vestibular sense
the sense of body movement and position, including the sense of balance; enabled by feedback from semicircular canals in inner ear
hair cells
finger-like projections on the basilar membrane that stimulate activity of the auditory nerve
cochlea
snail-shaped tube in the inner ear that contains fluid that moves in response to vibrations, stimulating activity on the basilar membrane
basilar membrane
area within the cochlea where hair cells are located
semicircular canals
fluid filled tubes in inner ear that provide information about movement of the head
Ernst Weber
early psychologist who established that the proportion of difference (rather than absolute difference) between two stimuli that is required for distinguishing between them is constant for particular types of sensation (e.g. weight, brightness, etc).
Gustav Fechner
often credited with founding "psychophysics" as a subfield of psychology; studied afterimages
David Hubel & Torsten Wiesel
Nobel-prize-winning researchers who discovered "feature detectors" within the brain
cochlear implant
a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea
sensory interaction
the principle that one sense may influence another, as when the smell of food influences taste
synaesthesia
when one sort of sensation (such as hearing a sound) produces another (such as seeing color)
olfaction
sense of smell
prosopagnosia
inability to recognize or perceive faces
gestalt
a perceptual whole; derived from German word meaning "form" or "whole
subliminal
literally, "below threshold"; stimuli too weak to be consistently detected
selective attention
ability to attend to only a limited amount of sensory information at one time
cocktail party effect
ability to selectively attend to one voice among many
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
proximity
Gestalt grouping principle; we group nearby figures together
similarity
Gestalt grouping principle; we group similar figures together
continuity
Gestalt grouping principle; our tendency to perceive smooth, continuous patterns rather than discontinuous ones
connectedness
Gestalt grouping principle; when objects uniform (in color or texture) are linked (no space exists between them) we perceive them as a single unit
closure
Gestalt grouping principle; we fill in "gaps" to create a full, complete object
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
retinal disparity
a binocular cue for perceiving depth; by comparing the images of the retinas of the two eyes, the brain computes distance. The greater the disparity (difference) between the two images, the closer the object
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)
Wolfgang Kohler
credited with founding Gestalt Psychology; also conducted studies of insight learning in chimps
relative height
monocular cue for depth perception; we perceive objects higher in our visual field to be farther away. Explanation for why the "bottom" of a figure-ground illusion usually is interpreted as the "figure
relative size
monocular cue for depth perception; if we assume two objects are similar in size, most people perceive the one that casts the smaller retinal image to be farther away
interposition
monocular cue for depth perception; if one object partially blocks our view of another object, we perceive it as closer
linear perspective
monocular cue for depth perception; parallel lines, such as railroad tracks, appear to converge with distance. The more they converge, the greater the perceived distance
light and shadow
monocular cue for depth perception; nearby objects reflect more light to our eyes...thus, given two identical objects, the dimmer one seems farther away. Also, shading produces a sense of depth consistent with our assumption that light comes from above.
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.
relative clarity
monocular cue for depth perception; objects that seem "fuzzier" or less clear are perceived to be farther away.
texture gradient
monocular cue for depth perception; a gradual change from course, distinct texture to fine, indistinct texture signals increasing distance
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 a specific stimulus as one thing and not another (for example, due to suggestion or expectations based on prior learning)
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
change blindness
when paying attention to a specific aspect of a visual scene, we may fail to notice other fairly obvious changes or presentations of stimuli; demonstrated by the door study and the gorilla illusion
McGurk effect
the same sound (e.g. "ba") can be perceived differently (e.g. "pa" or "fa") when the visual image of the mouth pronouncing it is changed; a classic example of "visual capture
bipolar cells
second layer of neurons in the retina that transmit impulses from rods and cones to ganglion cells; rods share these, but cones do not
retinal ganglion cells
the third layer of retinal neurons whose axons leave the eyeball and form the optic nerve.
gustation
sense of taste
embodied cognition
in psychological science, the influence of bodily sensations, gestures, and other states on cognitive preferences and judgments
priming
Activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response
nociceptors
Nerve endings that signal the sensation of pain.