Ms. Clough AP Psychology Unit 2 - Sensation and Perception

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 sensory 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.

selective attention

the focusing of conscious awareness on a particular stimulus.

inattentional blindness

failing to see visible objects when our attention is directed elsewhere.

change blindness

failing to notice changes in the environment.

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 percent of the time.

signal detection theory

a theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no single absolute threshold and that detection depends partly on a person's experience, expectations, motivation, and alertness.

subliminal

below one's absolute threshold for conscious awareness

priming

the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response.

difference (detection) threshold

the minimum difference between two stimuli required for detection 50 percent of the time. Also called the just noticeable difference (jnd).

Weber's law

the principle that, to be perceived as different, two stimuli must differ by a constant 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, such as sights, sounds, and smells, into neural impulses our brains can interpret.

wavelength

the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic versions of this vary from the short blips of cosmic rays to the long pulses of radio transmission.

hue (color)

the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth.

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.

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.

accomodation

the process by which the eye's lens changes shape to focus near or far objects on the retina.

rods

retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond.

cones

retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. These 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 and no receptor cells are located there.

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 stimulus, such as shape, angle, or movement.

parallel processing

the processing of many 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.

Young-Helmholtz trichromatic (three-color) theory

the theory that the retina contains three different color 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. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green.

audition

the sense or act of hearing.

frequency

the number of complete wavelengths that pass a point in a given time (for example, per second).

pitch

a tone's experienced 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.

cochlea

a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses

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 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.

cochlear implant

a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea.

kinesthesis

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.

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 or by information coming from the brain.

sensory interaction

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

gestalt

an organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes

figure-ground

the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).

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

a laboratory device for testing depth perception in infants and young animals.

binocular cues

depth cues, such as retinal disparity, that depend on the use of two eyes.

retinal disparity

a binocular cue for perceiving depth by comparing images from the retinas in the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object.

monocular cues

depth cues, such as interposition and linear perspective, available to either eye alone.

phi phenomenon

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

perceptual constancy

perceiving objects as unchanging (having consistent shapes, size, lightness, and color) even as illumination and retinal images change.

color constancy

perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object.

perceptual adaptation

in vision, the ability to adjust to an artificially displaced or even inverted visual field.

perceptual set

a mental predisposition to perceive one thing and not another.

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.

Gustav Fechner

1801-1887; Field: perception; Contributions: stated that the magnitude of a sensory experience is proportionate to the # of JND's that the stimulus causing the experiences above the absolute threshold

just noticeable difference (JND)

the minimal change in a stimulus that can just barely be detected

tip of the tongue phenomenon

experience of knowing that we know something but being unable to access it

receptor cells

Specialized cells in every sensory system of the body that can turn other kinds of energy into action potentials (neural impulses) that the brain can process.

receptive field

the region of the sensory surface that, when stimulated, causes a change in the firing rate of that neuron

qualitative dimension

One of the two dimensions of stimuli; determining what a stimuli is. coded and expressed by which neurons are firing

quantitative dimension

dimension focusing on how much of a stimulus there is

distal stimulus

In perception, it is the actual object or event out there in the world, as opposed to its perceived image.

proximal stimulus

In perception, it is the information our sensory receptors receive about the object.

bipolar cells

In the retina, the specialized neurons that connect the rods and cones with the ganglion cells.

serial processing

occurs when the brain computes information step-by-step in a methodical and linear matter

convergence

A binocular cue for perceiving depth; the extent to which the eyes converge inward when looking at an object

David Hubel and Torsten Wiesel

Nobel-prize-winning researchers who discovered "feature detectors" within the brain

Afterimage

A visual image that persists after a stimulus is removed.

color blindness

a variety of disorders marked by inability to distinguish some or all colors

tympanic membrane (eardrum)

the membrane at the end of the ear canal that relays vibrations into the middle ear

Habituation

decreasing responsiveness with repeated stimulation. As infants gain familiarity with repeated exposure to a visual stimulus, their interest wanes and they look away sooner.

relative size

a monocular cue for perceiving depth; the smaller retinal image is farther away

texture gradient (monocular cue)

a gradual change from a coarse, distinct texture to a fine, indistinct texture signals increasing distance. Objects far away appear smaller and more densely packed

Interposition

if one object partially blocks our view of another, we perceive it as closer

linear perspective (monocular cue)

Parallel lines appear to meet in the distance. The sharper the angle of convergence, the greater the perceived distance.

aerial perspective (monocular cue)

the haziness that surrounds objects that are farther away from the viewer, causing the distance to be perceived as greater

motion parallax (monocular cue)

Objects that are closer move past us more quickly than those in the distance, we infer distance from relative speed

retinal convergence

depth cue that results from the fact that your eyes must turn inward slightly to focus on near objects

Law of Pragnanz

perceptual organization will always be as regular, simple, and symmetric as possible

motion detection

perception of motion, either through the perception of its changing position, or through how we move our heads to follow the stimuli

Apparent motion/Phi phenomenon

- stimulus present in two locations within short time interval is seen as one moving stimulus

- no moving stimulus though! (i.e., no sensations of movement)

stroboscopic effect

images in a series of still pictures presented at a certain speed will appear to be moving

autokinetic effect

illusion, caused by very slight movements of the eye, that a stationary point of light in a dark room is moving