Psychology - Sensation & Perception

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"). 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)

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 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

semicircular canals

fluid filled tubes in inner ear that provide information about movement of the head

cochlear implant

a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea (sensorineural hearing loss)

sensory interaction

the principle that one sense may influence another, as when the smell of food influences taste

olfaction

sense of smell

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

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

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

phi phenomenon

an illusion of movement created when two or more adjacent lights blink on and off in rapid succession

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)

parapsychology

the study of paranormal phenomena, including ESP and psychokinesis

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

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

priming

Activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response

nociceptors

Nerve endings that signal the sensation of pain.

sensation

the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment

selective attention

The focusing of conscious awareness on a particular stimulus

inattentional blindness

Failing to see visible objects when our attention is directed elsewhere

Extrasensory Perception (ESPs)

the controversial claim that perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition

intensity

amount of energy in the wave determined by wave’s amplitude